Sort by

Hi, another book review for this book. I always feel something 自己実現的 reading this kind book, such another book is this. And it's occasionally suffocating if I were to quote from the book, like there is no way out. To summerize, the idea of 労働力商品の所有者としての労働者 and 消費社会 are the two where I find such 自己実現的 aspect in today's world. Its kind of ironic like what we believe to be logical isn't really logical given the logic of Capitalism, as said below. ウェーバーが"プロテスタンティズムの倫理と資本主義の精神"の末尾部分で...近代社会を激しく糾弾したのは...そのような社会に適合して生きる近代人が、実際には倒錯的なものでしかない自らの精神的態度<形骸化した"禁欲">を合理的なものとして誇っていることへの憤りゆえであった And maybe what we need is such spirit of observing the world just as it is, said by Spinoza, but I would like to find laughter and pity in such observation opposing to Spinoza as the author suggests haha. 笑うな、泣くな、ただ理解せよ With that all being said, there were couple of books introduced, which I would like to read if I were to go further on the topic. I was interested in how the transition from Imperialism, Fordism and 消費社会 can be explained by, fits in to the picture of 資本論. Maybe I should take a look into 大転換 and 消費社会の神話と構造 as recommended. Reading such books gives better understanding of how today came to "today", and how I came to end up in such "today". ポピュリズム大陸 南米 is rather for pure curiosity, as I'm thinking of visiting Argentina next August, and thought would be interesting to learn its history and how the current libertarian government came to place given below. 無論、ヨーロッパや南米などで、反新自由主義を標榜する政権が登場するなどしているが、その打倒には程遠い And yes, I also need to start studying Spanish as well haha. That's it for today's post!

I'm writing this post because I was impressed by what its written haha. The book explains 労働力の商品化 as 諸在価値 to be 通約可能. And argues how such 通約可能性 wasn't possible back in Greece for the reason below. ギリシア社会は奴隷労働にもとづいており、したがって、人間とその労働力の不等を自然基礎としていたのであるからである And it continues discussing the nature of 貨幣 specific to Capitalism as the 通約可能性 and its consequence as below. 本来、何らかの具体的欲望をかなえるために貨幣を求める、というのが欲望の正常なあり方だとすれば、ここで現れるのは貨幣それ自体への欲望である...倒錯性 Its interesting how it associates this 倒錯性 to those 規範 seen in 前近代社会. したがって、古代社会は、貨幣を、その経済的なおよび道徳的な秩序の破壊者として批判する It also associates this 倒錯性 to 抽象的な価値の蓄積 within the context of Max Weber's Protestantism on Capitalism ... プロテスタンティズムの職業生活の成功によって自己の救済を不断に確信せねばならないという信仰から合理的で勤勉な生活態度...を"世俗的禁欲"とウェーバーは呼んだが...それは、財の有用性を享受することではなく、抽象的な"価値"の蓄積へとすべての努力を振り向ける ... which leads to the modern Capitalism. And I believe this transition is what The Great Gatsby was depicting. この...勤勉さは、その原初の緊張感を失っていき、致富に成功した資本家は奢侈に流れもするだろう And below sounds to explain a lot of what I see in myself, and I'm impressed how things can be explained in such manner. ウェーバーが"プロテスタンティズムの倫理と資本主義の精神"の末尾部分で...近代社会を激しく糾弾したのは...そのような社会に適合して生きる近代人が、実際には倒錯的なものでしかない自らの精神的態度<形骸化した"禁欲">を合理的なものとして誇っていることへの憤りゆえであった Its just amazing how and where you get to "re"discover yourself. It always leaves me questioning about myself and the world, which I kinda like it haha. May be I should read プロテスタンティズムの倫理と資本主義の精神 for the start. Also, the book draws an analogy between 一般的等価形態 and Hobb's 社会契約説. The 社会契約説 seems to explain the underlying assumptions of today's world which I am unaware of, taking it for granted. Might be good to take a look at リヴァイアサン as well. By the way, I'm thinking of going to this tomorrow. I hope I now have a better understanding of surrealism, able to appreciate them a bit😅, after reading this book.

I'm preempting this book for now to read this book, its shouldn't take too long. The reason is somewhat descriebed as below... われわれの意識や感性、感覚、価値観、思考といった、普通われわれ一人一人が"自分のもの"であると信じて疑わないもののなかに、資本主義がどのように入り込んでいるのか...資本主義社会のなかに現に生きているわれわれが無意識的に自明のものとして見てしまう事象が、この人類史的視点のフィルターを通して見られると、相対化され、決して自明ではないものとして現れてくる...そのような...批判の...テクストとしての"資本論" ...related to the book to some extent. 歴史が予見不可能だというのは嘘である...確かに見通すことができるのは、未来の一般構造だけかもしれない。しかし実を言えば、一般的構造だけが、過去や私たちにが理解できる唯一のことではないか。だから、もしあなたが自分の時代をはっきり見ようと願うならば、遠くから見るべきなのだ...クレオパトラの鼻が見えなくなるちょうどその距離からである With that being said, seems like I'm a kind of guy who can't stand being aware of unaware haha. われわれはそれでも無自覚でいられるだろうか By the way, I'm listening to this song repeatedly these days🎵.

The book was great giving lists of novels, describing how they can be characterized and fits in the context of "American". And there are couple of books that was introduced which I thought might be good to read in the future. - ライ麦畑でつかまえて - カッコーの巣の上で - キャッチ＝２２ - 見えない人間 I would definitely read "Inivisible Man", maybe I'll try others as well, but all the above I'm interested in Richard Powers, a novelist introduced at the very end of the book. In the epilogue, the book gives some advice for how and what can one expect from reading books, as below. 自分の読み方について考える時には、相手に自分を活性化してもらうという肯定的な発想にせよ他者を消費するという否定的発想にせよ、とにかくそうした非対称的な発想以外の道はないか考えてみることはできる Richard Powers is introduced as where we can find such 非対称性 in relation between 自分 and 他者 in his novels. パワーズという作家の大きな特徴は、世界を思い描く上で、意味づける自分と対象、自己と他者、というふうに非対称的な関係を根底にそえるのではなく、自分と対象<...対象が一枚の写真であれ、一人の他人であれ、第一次世界対戦であれ...>との関係がまずあって、刻々と変化していくその関係から、そのつど自分と対象とが分泌されていく And I believe such experience described as below are those moment when we become aware the 対称性 of today in relation to all the other times in the course of history. いわゆる"近代文化"-が、自らを決定的であるとする思い込みこそ、視界に生じた信じがたい頑迷さと狭隘さではないのか、という漠然とした直感がその根底に見出される。そしてそのように感じる時、私たちは自分たちが狭く閉ざされた場所から逃れ出て、再び星空の下に立ち、最善のことも最悪のこともすべてが可能な、真正で深遠で、恐ろしく見通しのきかない底しれない世界に出たのだという、えも言われぬ印象を持つのである Also, it should be the kind of relation which E.H. Carr describes as below. 過去は現在の光に照らされて初めて知覚できるようになる。現在は過去の光に照らされて初めて十分理解できるようになる By the way, I found out that Richard Powers is graduate of UIUC. I wonder if can go back to school and take his English courses haha.

Its after I started reading this book that I realized that its similar to this book, although I haven't read it yet, in a sense its about characterizing the society at the time. With that being said, and keeping in mind that the book was written in 1920s, it's interesting that the book describes what the basis use to be for people claiming their rights, which seems to differ from today's society of "singularity". むしろ現代(1920s)の特徴は、凡俗な魂が、自らを凡俗であると認めながらも、その凡俗であることの権利を大胆に主張し、それを相手かまわず押し付けることにある Note that I haven't read the book, so I might be totally wrong, let's see. But the book is still interesting itself finding out how the author lived in 1920s observed his society back then. Personally, I would rather once again take it as an ideal than taking it for granted ignorantly :) 普遍一般の人間個人の主権に関する理念や法的理想だったものが、いまや(1920s)...一つの心理状態へと移行したのだ And there is this moment that you discover what used to appear as 必然, in other words 心理状態, was one of mere possibility, reducing to a matter of choice, and everything starts to seem possible... - added as of 2025/06/19 いわゆる"近代文化"-が、自らを決定的であるとする思い込みこそ、視界に生じた信じがたい頑迷さと狭隘さではないのか、という漠然とした直感がその根底に見出される。そしてそのように感じる時、私たちは自分たちが狭く閉ざされた場所から逃れ出て、再び星空の下に立ち、最善のことも最悪のこともすべてが可能な、真正で深遠で、恐ろしく見通しのきかない底しれない世界に出たのだという、えも言われぬ印象を持つのである .. maybe because of the below reason. すなわち私たちの生とは、瞬間ごとに、そしてすべてに先立って、自分にとって可能なものについての意識であるということなのだ By the way, I can somewhat see myself in the song, don't know how I can fit in at this "party". Like nobody's lookin' me in my eyes and everyone's got so much to say. But I'm told that it's where I'm suppose to be. Makes me wonder if I could sneak out the back🎵.

Today's post is bit different from what I have been posting lately. The purpose of this post is to leave a note on places I was interested by reading this book, which hopefully I can visit one day. The last chapter of the book is about "utopia". It discusses how the notion of utopia has _not_ changed over time ever since the time of Greece and how it can be characterize by this and that. The first characteristic I was interested by is how lights are homogeneously arranged in utopian society. The book describes that such homogeneous arrangement of light does not create any kind of contrast that is provided by shadow, like found in fluorescent light. The opposite, meaning having contrast, is those that can be found in light bulb. The book interprets such homogeneous manner of light in utopian society as below, which reminds me of what Foucault was discussing. トーマス・モアの"ユートピア"には照明のことは書かれていなかったと思うけれども、生活には闇の部分がなく、隅々までも監視が行き届いているという意味では、大体の古今のユートピアはどれも基本的にいわゆる明るい社会なんです With the above being said, the books says that people of Paris once gone against such use of light. パリ・コミューンという1871年の革命のときに...民衆が闇をかえせと叫んで、パリの街灯をひとつひとつ壊して歩いたという And the city I want to visit is Prague as the book says its one of the city in Europe which contrast created by light is beautiful. 点々とオレンジ色のオレンジ色の街灯のならんでいるヨーロッパの町で、もっとも街灯の美しい町のひとつとしてプラハを挙げるならば、そこでは光と影がじつにみごとな起伏にとんだ空間を作り出している。歩くと自分の影がいっしょに動いてゆく Another characteristic that I found interesting in utopian society is its preference over linear arrangement of a city. Its interesting how those linearity found in Greece can be interpreted as "Rationale" ... たとえばアテネはずいぶん奇妙な町です...規則性と反復性の傑作といっていいパルテノン神殿が立っている...あの植谷雄高でさえ、パルテノン神殿に地中海の理性を感じたと記憶します ... and how its different from those linearity found in Pyramid in Egypt and other places. もちろん直交性を持った都市は以前からありました...たとえばエジプトのルクソールに行くと、神殿そのものが直線的ですから、まわりの道もほぼ直線になっていいます...ミレトスの直線は神によって与えられた直線ではなく、人間の(合理的)直線なんです And lastly, the book mentions how the linearity can be interpreted in a context of Orientalism considering "Rationale" as a Western representation. One such example the book gives is the city of Miletus in Turkey, considering how Miletus was neighboring "Asia" back when there was a Persian Empire. The book draws a contrast between Europe and Asia by considering the "Rational" as Western, against "Asia" described as below. そのころにプラトンが登場したんですね。彼には守るべきものがあったわけです。それは、ギリシアが既に高度に推しすすめていた理性というものです...それを象徴する幾何学的に構成された都市...ミレトスに...アジアが侵入してくるのが怖かったんですね。ここで言うアジアというのは、広いアジア的なものです...規則性、反復性がない...エキゾティックで...得体の知れない魅力的なもの Maybe I should read this book in regards. Also, back to how lights are arranged in utopian society, its interesting how Asian cities are getting more utopian today where it was "Asia" that represented the very opposite. Its interesting by how those nature found in the listed cities are still able to be seen in the very society that I live today. And if I were to consider "today" as a point in a history as just like those society once used to be, I see something within those cities that I can associated to myself. Its interesting that the very nature seems to stay the same over time, in fact I can still see them in The Hunger Game haha. The books also shares how those terms like Fantastic, Féerique and etc differs each other. I wonder which term is appropriate for describing Midnight in Paris. Maybe Fantastic? Please let me know if you can tell, because I can't yet😂. That's it for today's post. I hope I can write a post like this more often. See you in the next! --- Diary --- I went to Hakone today and it was such a great trip. Just wanted to keep a note so that I can remember haha.

This is a short note for myself, somewhat related to the reason why I want to read Society of Singularities. I haven't read the book yet, but I believe there is an attitude prevalent in such society, which attitude I am aware of my very self, something like below described in the book. "あれかこれか"の決断が迫られる状況は忌避される。さまざまな対立に主体的に関与するのというのではなく、多様性が強調される It could be about any kind of social matter, such as this against that. And I believe there needs at least some kind of attitude towards to make discussion meaningful. With that being said, I feel like its an responsibility of mine as one taking part in society to be aware of issues around the world and having my own attitude towards them. And the below quote from Wright Mills well states what I have in my mind in regards. 私は客観的で（objectvive）であろうと努めてきたが、コミットしてこなかった（detached）つもりはない By the way, I applied for the next year Masters tickets hoping as a gift for the coming father's day. Let's see if I can get one😉

This is the review, or rather my takeaway, of the book. I want to go over the book by quoting the two lines found in the book from E.H Carr. The first quote below, I believe, reflects the very argument that was repeated in the book... 過去は現在の光に照らされて初めて知覚できるようになる ... which is below. The above quote well points out that there always is a perspective, and its the perspective(現在) that allows us to look at(知覚) the past. 世界に起こることは無限であり、なんらかの意味づけをしなければ、それ自体に意味はない。どの事実をどのように整理して理解可能にするのか...事実は一定の観点に関係づけられてはじめて事実として浮かび上がる The second quote, from E.H Carr as well, is given as below. 現在は過去の光に照らされて初めて十分理解できるようになる Note that its not 知覚 as in the first quote, but its 理解. As far as I understand, the point is that we can only understand ourselves(現在) when there is a past that allows to place and study ourselves in relation to. The books wraps up with below line. I think the kind of discussion is needed, not just on the matter of 中立, but to really any subject out there in the world. この終章で考えたいのは、中立を強く求める、そうした時代についてである。さまざまな分野を横断して、なぜかこの時代に支配的になっている雰囲気を問題にしたいと思う。今日の雰囲気はいつの時代にも変わらず存在してきたものではない Which leads me to question the world that I see today, and its the question that I feel is the most interesting one out there.

I was watching this movie and made me want to write about this book, which I wasn't really think of writing about it. To start, people may have different opinion on the movie, but I personally I liked it. Its about a kid who immersed himself in jazz, and a professor who just keep pushing the kid until he breaks. And I can kind of relate myself to this kid as I think I have this tendency of getting lost in my own world, unable to see the other possible choices. And this I believe can be said to various aspects in life, but here I will discusses in terms of jobs quoting from the book as below. 組織が不安定になっても、社会のなかにおける"職業"という軸をしっかりしていれば、そこから距離をとり、職場のなかでの仕事を茶化したりズラしたりすることができます。"ポスト日本型雇用社会"における茶化し/ズラしのためには、組織の安定に左右されない、社会のなかにおける仕事="職業"という考え方が必須で、それこそ、現代日本において、かりあげクンのように"軽やかに"いきるための条件なのです And what I like about the books is that it extends this way of "humorizing" to the life itself, finding the common ground in the way how the people lived back in Soviet Union. 後期社会主義では...彼らは、権威的な言説を茶化したり、骨抜きにしたり、新しい意味を与えたりしながら、一見抑圧的な体制の下にありながらも、"軽やかに暮らし""とても楽しい生活をしていた"のです...かりあげクンは、堅苦しい会社の仕事から"超越(ヴェ二)"した存在で、作品では、彼が、"軽やかに暮らし""とても楽しい生活をして"いる様子が描かれます。彼は、後期社会主義のソ連に生きていた人々と同じく、"システムの内部にいてその一部として機能しながら同時にその枠外の別の場所にいる生き方"(ユルチャク)をしていると言えるでしょう Note that I do _like_ my job, but it can't be all that's out there, so as every other things in life. Also I occasionally get lost in those books I read, makes me feel deadlocked and little discouraged, which is kind of paradoxical as they are suppose to help me figure out those lingering question of mine. Maybe his "軽やかさ" is exactly what I need now in my life haha. By the way, I like jazz and listening to them makes me want to appreciate the world just as it is, not sure myself what that suppose to mean though😂. There is a nice jazz bar in Shinjuku, which I haven't visited for a while. Hope I can visit the place once again during this summer.

A while ago, I quoted Hideharu Ando's description of 価値自由. There was a follow up on how his personal experience during the war had lead him to study the idea, and I wanted to make a note of it. It discusses the conditions on how one can be critical on something, and how his personal experience is tied to his study as below. 事実と価値の分離が可能になる条件は、一つの現実に一つの、その現実を正当化する価値がへばりついているという状態からの離脱である。一つの現実（事実）を異なる観点（価値）から把握する可能性がなければ、そしてそうした異なる、複数の観点がそんざいするということを真剣に受け止めたうえで自分と社会を考察するという構えがなければ、ウェーバーの方法論はまったく意味をなさない。安藤はこのことを軍隊生活とその後の研究生活で考え続けた。彼が価値自由を、自分自身の生き方の問題、そしてエートスの問題として引き受けたのも、このためであった And it continues as following, which I see interesting correspondance between Foucault's study unraveling the conditions for those human science came to exist at first place. 安藤の価値自由論は、学問論であると同時に、学問に先立つ前提を批判的に問い直そうとする理論である。無批判にある一定の前提で思考しているかぎり、目の前の、所与の社会秩序を相対化することはできない。このような場合には、wertfrei な態度は現状追認にしかならない。別の言い方をすれば、現実から距離をとって批判的に考察することができる、強い主体、ないしそれを可能にするエートスがなければ、目の前にある現実から自由になることはできない。安藤の読解では、ウェーバーの学問論と宗教社会学が独自の仕方で連結している I would like to queue the book for the next, but there are already few awaiting in the line, let's hope it wont get stalled for too long haha.

I finished reading the book. I wasn't really thinking of writing another post about the book but I changed my mind. The book says that Foucault once mentioned about his role as below. 人々が、自分で考えているよりもはるかに自由なのだと教えること、人々が自明で真理だと信じているいくつかのテーマが、歴史の特定の時点に作り出されたものであり、このみかけの上での自明性は批判し、破壊することができるものだということを示すことです。それが知識人の役割です。 And I realize that the books, not just his but all those other books as well, are playing this very role for me. It also mentions about the questions that he was trying to answer, and I share the same perspective on the kind of questions that needs to be answered, which is listed as below. - 主体の条件 - どのような知を"真理"として構成し、それを"真理"として確信するのか - 歴史的な条件のもとで、どのような条件において、ある対象が知の対象となりうるか - 主体は真理を獲得したと考えることで、どのような満足と権力を獲得するか Despite how complicated they all sounds, I believe its just saying think yourself, and books will help along the way😆. And I actually find it's something quite interesting to think about. By the way, I always find myself feeling strange yet peaceful like I'm back home listening to those songs from childhood. The song must had been played a lot on the radio back then haha. Its nice to have some place, photos, songs, or really anything you can find peace within🎵.

I'm back reading this book. Little note on the difference between 没価値 and 価値自由(Wertfrei) put it into my own words as a reminder for my own sake. The book quotes Hideharu Ando's description of 価値自由 as below. And how it differs from 没価値, which is more close to the seemingly objective notion of 中立, is what I want to emphasize. "ヴェルト・フライハイト"とは、価値理念や価値判断をできるだけ鮮明に（とりわけ自分自身に対して鮮明に）させることによってそれを自覚的に自己統制することを意味する The book continue as below ... 研究者が主体として価値とどう向き合うかが、安藤にとって重大な問題関心であった。自分の価値理念を自覚化することのない主体は容易に周囲の空気に流される...没価値的な学問はこのような主体のあり方と結びつきやすい ..., and I think this is not just something applicable to academic approach, but also to us regarding how we see the world considering that we are placed in our own unique situation. I remember that the book mentions about the origin of moral as Latin's mores and how its fragile which changes over time and society in the history, something like described as below in the book. エートスは"住み慣れた場所"を意味するギリシア語のἦθοςに由来し、"習慣"や"性格"を指す言葉である。もちろんエートスは倫理（ethics）の関連語でもある。しかし両者には違いもある。倫理ないし倫理学は、思考によってある程度まで整合的に考えられた理論のことである。これに対してエートスは、そうした理論とゆるやかに結びつきつつ、ある時代のある社会集団に共有され、彼らの行為を導くような、習慣化された倫理的態度を指す。エートスはラテン語のモーレス（mores）に対応する。 And I wonder what's out there that I could to do considering what I wrote above, and books seems to be a good place to start with ;)

Hi, here's another book review! I still haven't finished the book yet but I would like to summarized my short take away from it. I won't write all the details as I wrote a lot about it in the past posts. I would just say there was a lot of idea that I was seeking at the moment, and as of this moment. Again, its nice to have them put into words. Even though it was little discouraging and indeed suffocating as quoted below😂. フーコーの権力の分析が深まっていけばいくほど、生の可能性が失われていくような印象すら受ける。権力的な関係のうちでの抵抗の可能性が失われ...権力的な網の目に絡まれとられてしまうような理論の運びである...近代的な社会がまず規律的な権力の社会として捉えられ...社会にふさわしい身体と精神をもつ主体が構成される...これは息がつまるような理論である Also, it was interesting to see the book referring to Louis Althusser as I remember reading his book while I was in college. Seems like I'm coming back and forth haha. Another interesting reference I found is that the book which I just started reading mentions about how its based on Foucault's this and that book. Although I'm still not yet familiar with the idea of discours(言説), I'm willing to take a look into those books so that I can see how it can be apply to Orientalism. Maybe later, once I catch my breathing :) Lastly, there was this quote in the book about the seemingly neutral notion of Orientalism disattached from political discussion. "真の知識"が基本的に非政治的であるとする一般的でリベラルな多数意見というものは、知識の生み出される時点でその環境としてある、たとい目には見えずとも高度に組織化された政治的諸条件を、いかにして覆い隠すものとなっているのか。本書が明らかにしようとしているのはその点である I see the statement is also very true in today's everyday world, and I believe its something that we should carefully consider what kind of knowledge that we are dealing with. Again, this is something that I recognize from Max Weber's Wertfreiheit(没自由). And I'm looking forward to see how the book untangles the seemingly neutral notion of Orientalism as said below. "インドやイギリスに関するあらゆる学問的知識は、総体としての政治的事実によって何らかの意味で色付けされ刻印を押され侵害されているのだ"ということとは...本書でオリエンタリズムに関して私の言わんとするところなのである...なぜなら、人文科学におけるいかなる知識の生産であれ、その著者が人間的主体として周囲の環境に巻き込まれている... That's it for today's post! I wonder if there might be some insights into how Japan is portraited in today's tourism, which I kinda like it haha.

As I think more and more, I occasionally get this depression having hard time seeing value or faith in those things that considered to be a priori in life, feels like nothing left to believe in to start with. Sometimes its hard to keep my heads up... Maybe I must have a faith and start thinking the kind of changes that I may be able make. --- wrote as of 5/25 --- Isn't this the very question that I am trying to ask myself, and the very reason that I am willing to learn, so that I can live with little bit of confidence ;)

Little note on my thoughts while I was reading this article. I noticed that people involved in the situation covered in the article fits into the picture discussed in this book. The book discusses how America has changed over time, which resulted in society getting more deterministic in terms of their course of life, given their social and economic backgrounds. Considering how such current situation has been shaped over time and the fact we are at least placed in one of such situation of our own, it makes me wonder how where in the society which I belong to has came to be created. By the way, I think its important that you put your feelings or those intangible idea into words at that very moment, it's hard to come back and put them back together once its lost.

Books occasionally provokes this sense of feeling that I'm more of a object(客体) of interest which needs to be studied within the context of the society(社会) and the history(時代) that I live in, leading me to lose the sense of subjectivity(主体). I think this sense of feeling is what keeps me thinking, questioning, and reading etc. I think below line from this book describes the idea. 自然のことものを対象とする物理学や化学のような学問とは異なり、学問の対象が同時にその主体であるために、厳密な科学性に到達することができないことにある I believe there is some idea shared among the above and below line from this book in terms of subjectivity. I also see something similar in the discussion of Wertfreiheit(没自由) by Max Weber. May be I'm wrong though. 人間には感情や自己の利益に左右されずに、合理的に判断を下すことのできるための能力がそなわっている...判断という活動そのものの力で独自の原則を作り出すことができる But at the end, if we were a product of the society and history we live in, isn't those society and history that we should be studying to understand ourselves? --- a little insight into what I wrote above as of 5/14 --- There must be a condition for such question to arise explaiend as below in the book . 近代の知の大きな特徴は、考古学的な変動によってこのまなざしと表の空間が崩壊し、そこに生身の人間が登場することである。人間は"知にとっての客体であるとともに認識する主体として、その両義的な立場において登場する"。 If the above can be said, there is where the question comes in. "純粋理性批判"においてカントは、批判哲学はコペルニクス的な転換を意味すると誇ったが、これは人間の知が人間の認識の有限性によって初めて根拠づけられるという確認であった...すなわち、人間の認識と知の真理の根拠は、人間が物自体ではなく、現象しか認識できないという認識能力の有限性そのもにあるとされたのだった。 --- another follow up as of 2025/05/19 --- I wondered if I should write this as a new post, but I'll write this as a follow up for this post. The line below is from the book. 真理とは、誰がそれを真理として信じるかによって、大きく意味を変えるものであり、思想を真理として信じる主体の分析なしには、真理そのものの概念を分析しても、意味がないことになる And it discusses about the nature of "the" truth as following. <本質>がどのように歴史的な経緯によって真理として形成されたのかを分析する...真理という概念は、この歴史性を隠蔽して、なにものかの"本質"であるかのように振る舞うものである And it describes "the" truth as following. 真理とは論駁されないという特徴をもつ誤謬にすぎず、歴史的な価値をもつものにすぎない And I agree with the above statement, as far as my understanding, which is for the reason described by the following statement from the book. 個々の主体から離れた真理というものはなく、真理はつねに一つの視点からみられなければならないこと示すものである But at the same time, if I were to place myself in a such mere existence relative to society and history, I get little discouraged that I feel there is no value in such notion of being "myself"😅. This book might be the one for me to take a look at next.

This is a short follow up to the last post. I occasionally use the term "better". I thought it might be a good idea to clarify what I mean by the term when I use in this blog as I believe it can deliver so many things when used depending on the context. Let me first state that, jumping to the conclusion, I try to keep the word "better" within the extent of technical sense. What I mean by that is that the word "better" I use is not based(to the extent that I'm aware of) on any kind of "argument" of mine. I think the below quote from this book gives the sense of idea which I have in my mind. 彼(ゴルトシャイト)からすれば、資本主義経済のネガティブな作用が顕在化する中で、より"人間的"な経済を主題化し、その方向で"進歩"を語ることは、混乱しているどころか、極めて筋の通った議論に思えたはずである。しかしウェーバーからすると、"人間的"というのはあまりにも多義的である。これについて一義的に進歩を論じることはできない。ゴルトシャイトにとっての"人間的"という評価は別の人にとってはそうではないかもしれない。別の人は別の基準で"人間的"を論じる可能性があるし、実際そうしているかもしれない。 But with the above said, there is this below quote that I found in this book. And if I were to make any kind of "argument" regarding "progress", it would be something similar to his. Maybe I will take a look at his book for the next. And yes, there also is this book that I bought quite a while ago that is still piled up in my room. Maybe now is a good time to revisit the book. 歴史の進歩とは、自らの責任を問われ必要のないことで負わされる"不条理な苦痛"を減らすことだ - 市井三郎 By the way, listening to this song while I play around with the DSLR from my college years make me feel things are still the same... Am I just being nostalgic or I actually haven't made any kind of progress ever since😅?

Image today is another day that you are making this world a little better place, and I can't think of anything more exciting😆. It's as exciting as this song, no!?

Listening to Tupac makes me feel I'm no longer young in a sense that I am responsible in one way or the other just by taking part in a society. I like the feeling that there actually is something, no matter how trivial that might be, that I can take part and be responsible. Let's see if I can figure this out😉.

Hi, recently I have been looking into how user processes are prepared. Today's post is about the how user process and thread are being prepared in terms of allocated memory. When a new process or thread being created, it calls clone system call. If you want to create a thread, you can pass CLONE_VM flag to the system call. One of the difference between a process and thread is that wheather it shares its memory space or not. The latter does but the former does not, and today's post is about looking into this difference. In order to see the difference, I prepared a program which ① the parents process assignes a variable with 5, and ② the cloned child process rewrites the variable with 10. The difference mentioned earlier can be seen at the ② point. Let's first see how the process looks like. Below shows that the PID 1628 is the parent and the 1629 is the child. crash> ps | grep clone 1628 1601 0 ffff94fd4a271c80 IN 0.1 2628 1336 clone 1629 1628 0 ffff94fd4123b900 IN 0.1 2628 884 clone crash> Now let's take a look at the physical address correspoding to the variable's virtual address which is 0x404068. You can see the corresponding physical address is 17bfe068. As expected, the value at the address is still 5 as the child process does not share the address space. crash> vtop -c ffff94fd4a271c80 404068 VIRTUAL PHYSICAL 404068 17bfe068 ... crash> rd -p 17bfe068 10 17bfe068: 0000000000000005 00000000014b72b0 .........rK..... ... crash> However, if you take a look at the threading, you will see the varible is now changed as the child shares the same address space and rewrites the variable. crash> ps | grep clone 1714 1601 0 ffff94fd44e2d580 IN 0.1 2628 1396 clone 1715 1714 0 ffff94fd41291c80 IN 0.1 2628 964 clone crash> vtop -c ffff94fd44e2d580 404068 VIRTUAL PHYSICAL 404068 1161e068 ... crash> rd -p 1161e068 10 1161e068: 000000000000000a 00000000004c32b0 .........2L..... ... crash> That's it for the today's post. Note that I used x86 for this experiment as vtop on arm64(below) did not work. I wonder why🤔. Might be fun looking into it. crash> vtop -c 11884 aaaae706c84c VIRTUAL PHYSICAL vtop: invalid structure member offset: mm_struct_mmap FILE: memory.c LINE: 4007 FUNCTION: vm_area_dump() [/usr/bin/crash] error trace: aaaae706c84c => aaaae706456c => aaaae7101180 => aaaae71010ec vtop: invalid structure member offset: mm_struct_mmap FILE: memory.c LINE: 4007 FUNCTION: vm_area_dump() crash>

Hi, I wanted make a post on how the first process gets initiated as I have been playing around with qemu recently. Specifically, I will describe how the parameters below lead to the /sbin/init, which has the pid of 1. admin@ip-10-0-16-6:~/busybox/busybox$ qemu-system-aarch64 -M virt -cpu cortex-a72 -m 1024 -kernel /boot/vmlinuz-6.1.0-13-cloud-arm64 -initrd /home/admin/busybox/busybox/rootfs -append "root=/dev/ram0 rdinit=/sbin/init nokaslr" -nographic Let's start with the source code. After the kernel finishes the initilization of this and that, it gets ready for the first process and calls rest_init. The function inits the rest and calls kernel_init, and then run_init_process gets called. Now back to the arguments and see what it's doing. If you take a look at the man page of initrd, it says that -initrd gets uncompressed onto the /dev/ram0, which then mounted as the inital root file system. Here I found little confusing is that if you specify root as /dev/ram0, the initial root file system, which is /dev/ram0, will remain as the normal root file system. Let's make sure that the first run_init_process is the one being called for initiating the first process in the case of using /dev/ram0 as the normal root file system. Here you can see that the execute_command has /sbin/init, the program specifed by rdinit from the normal root file system which now is the /dev/ram0. (gdb) print ramdisk_execute_command $1 = 0xffff00003fdf0196 "/sbin/init" (gdb) print execute_command $2 = 0x0 (gdb) By the way, don't forget to specify "nokaslr" for the boot parameter. Otherwise, break points won't work😑. That is it for this post!

Hi, today I wanted to make a short post that I now have a working kernel built-in ARP(reply) stack😎. Although the stack can't yet handle ARP request, my stack is now able to receive packets from local peers! Here are the output showing the windows sending arp request and raspberry pi (my stack!) replying to the request. C:\WINDOWS\system32>arp -a Interface: 192.168.10.2 --- 0x8 Internet Address Physical Address Type 192.168.10.1 fc-99-47-12-26-7a dynamic 192.168.10.255 ff-ff-ff-ff-ff-ff static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 239.255.255.250 01-00-5e-7f-ff-fa static Interface: 172.21.176.1 --- 0x2b Internet Address Physical Address Type 172.21.179.85 00-15-5d-4a-0e-39 dynamic 172.21.191.255 ff-ff-ff-ff-ff-ff static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 224.0.1.60 01-00-5e-00-01-3c static 239.255.255.250 01-00-5e-7f-ff-fa static C:\WINDOWS\system32>ping 192.168.10.3 Pinging 192.168.10.3 with 32 bytes of data: Request timed out. Ping statistics for 192.168.10.3: Packets: Sent = 1, Received = 0, Lost = 1 (100% loss), Control-C ^C C:\WINDOWS\system32> ┌──(kali㉿kali-raspberry-pi)-[~] └─$ dmesg | grep my_arp_rcv [ 93.757253] my_arp_rcv(): address of skb　00000000f1642941 [ 93.757324] my_arp_rcv(): address of arp header0000000063ca06a6 [ 93.757349] my_arp_rcv(): sender IP address of 34252992 [ 93.757371] my_arp_rcv(): target IP address of 51030208 [ 93.757391] my_arp_rcv(): the arp requsest is for IP protocol [ 93.757430] my_arp_rcv(): found matching ip interface [ 93.757484] my_arp_rcv(): successfully sent an arp response C:\WINDOWS\system32>arp -a Interface: 192.168.10.2 --- 0x8 Internet Address Physical Address Type 192.168.10.1 fc-99-47-12-26-7a dynamic 192.168.10.3 e4-5f-01-d3-5b-d9 dynamic --> here the entry is added, fc-99-47-12-26-7a is the MAC of pi 192.168.10.255 ff-ff-ff-ff-ff-ff static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 239.255.255.250 01-00-5e-7f-ff-fa static Interface: 172.21.176.1 --- 0x2b Internet Address Physical Address Type 172.21.179.85 00-15-5d-4a-0e-39 dynamic 172.21.191.255 ff-ff-ff-ff-ff-ff static 224.0.0.22 01-00-5e-00-00-16 static 224.0.0.251 01-00-5e-00-00-fb static 224.0.0.252 01-00-5e-00-00-fc static 224.0.1.60 01-00-5e-00-01-3c static 239.255.255.250 01-00-5e-7f-ff-fa static C:\WINDOWS\system32> I recently started this service called scrapbox.io for keeping all the notes taken while I build my programs. Below is the link to the note while I was doing some debuggings for this arp reply stack. https://scrapbox.io/everydaymemo/arpリプライのデバッグ

Hi! There is this holiday called Golden Week in Japan. It is a week long holiday and I wanted to share this project I was working on for almost 12/7😅. Its about building your own networking stack from device(using TAP) to socket. It is a great project for those who want to understand how OS networking stack works behind the Linux kernel. Below is the github link I was following along the project. https://github.com/pandax381/microps https://github.com/sititou70/klab-protocol-stack-tutorial I've gone through each stack and it really deepened my understanding of how OS handles data arriving to its physical devices and sending all the way up to sockets assigned to each application. I am thinking of sharing some of the key concepts of each stack and how they passes data to each other in the future posts! For today's post, I just wanted to share a modification that I made from the original program regarding the TCP stack. I enabled the TCP stack to be able to establish a active connection to a server on the internet and fetch some random content. Of course, the established connection can't just abandon the connection😏. It has to participate in the process of terminating connection passively. I modified the code to complete the entire procedure of such TCP connection. Below is the log from the local program, the one uses the DIY network stack. 00:18:18.434 [D] tcp_open_rfc793: connection established: local=192.0.2.2:7, foreign=194.195.86.83:8080 (tcp.c:1172) 00:18:18.434 [D] tcp_output_segment: 192.0.2.2:7 => 194.195.86.83:8080, len=100 (payload=80) (tcp.c:417) src: 7 dst: 8080 seq: 1804289384 ack: 3543150099 off: 0x50 (20) flg: 0x18 (---AP---) wnd: 65535 sum: 0x30fe up: 0 00:18:18.434 [D] ip_output_core: dev=net1, iface=192.0.2.2, protocol=TCP(0x06), len=120 (ip.c:477) vhl: 0x45 [v: 4, hl: 5 (20)] tos: 0x00 total: 120 (payload: 100) id: 131 offset: 0x0000 [flags=0, offset=0] ttl: 255 protocol: 6 (TCP) sum: 0xdfe3 (0xdfe3) src: 192.0.2.2 dst: 194.195.86.83 00:18:18.435 [D] arp_resolve: resolved, pa=192.0.2.1, ha=8e:6e:37:e9:d1:92 (arp.c:357) 00:18:18.435 [D] net_device_output: dev=net1, type=IP(0x0800), len=120 (net.c:189) 00:18:18.435 [D] ether_transmit_helper: dev=net1, type=IP(0x0800), len=134 (ether.c:108) src: 00:00:5e:00:53:01 dst: 8e:6e:37:e9:d1:92 type: 0x0800 (IP) Data with the size of 80 was sent. Closing the connection. ... 00:18:18.562 [D] tcp_input: 194.195.86.83:8080 => 192.0.2.2:7, len=67 (payload=47) (tcp.c:996) src: 8080 dst: 7 seq: 3543150099 ack: 1804289464 off: 0x50 (20) flg: 0x18 (---AP---) wnd: 29200 sum: 0xc768 up: 0 +------+-------------------------------------------------+------------------+ | 0000 | 48 54 54 50 2f 31 2e 31 20 34 30 30 20 42 61 64 | HTTP/1.1 400 Bad | | 0010 | 20 52 65 71 75 65 73 74 0d 0a 43 6f 6e 6e 65 63 | Request..Connec | | 0020 | 74 69 6f 6e 3a 20 63 6c 6f 73 65 0d 0a 0d 0a | tion: close.... | +------+-------------------------------------------------+------------------+ 00:18:18.562 [D] tcp_output_segment: 192.0.2.2:7 => 194.195.86.83:8080, len=20 (payload=0) (tcp.c:417) src: 7 dst: 8080 seq: 1804289464 ack: 3543150146 off: 0x50 (20) flg: 0x10 (---A----) wnd: 65488 sum: 0x029d up: 0 ... 00:18:18.565 [D] tcp_input: 194.195.86.83:8080 => 192.0.2.2:7, len=20 (payload=0) (tcp.c:996) src: 8080 dst: 7 seq: 3543150146 ack: 1804289464 off: 0x50 (20) flg: 0x11 (---A---F) wnd: 29200 sum: 0x905c up: 0 00:18:18.565 [D] tcp_output_segment: 192.0.2.2:7 => 194.195.86.83:8080, len=20 (payload=0) (tcp.c:417) src: 7 dst: 8080 seq: 1804289464 ack: 3543150147 off: 0x50 (20) flg: 0x10 (---A----) wnd: 65535 sum: 0x026d up: 0 ... 00:18:18.565 [D] tcp_output_segment: 192.0.2.2:7 => 194.195.86.83:8080, len=20 (payload=0) (tcp.c:417) src: 7 dst: 8080 seq: 1804289464 ack: 3543150147 off: 0x50 (20) flg: 0x11 (---A---F) wnd: 65535 sum: 0x026c up: 0 ... 00:18:18.689 [D] tcp_input: 194.195.86.83:8080 => 192.0.2.2:7, len=20 (payload=0) (tcp.c:996) src: 8080 dst: 7 seq: 3543150147 ack: 1804289465 off: 0x50 (20) flg: 0x10 (---A----) wnd: 29200 sum: 0x905b up: 0 Connection is closed passively. And here is the log from my web server hosting this web site. By comparing the logs, you can see that the TCP 3 way handshake at the beginning actively initiated by the local program of mine. At the end, the server is the one that initiating the termination of the connection as it has finished sending all the data, which in this case is a "400 Bad Request".... I made few modification on the program so that the local program can handle the state transition associated with the active establishment and the passive termination of a connection. root@ryofslife:~# tcpdump src host 180.56.119.152 -vvv ... 15:18:18.426463 IP (tos 0x48, ttl 233, id 129, offset 0, flags [none], proto TCP (6), length 40) p9209152-ipngn9901marunouchi.tokyo.ocn.ne.jp.60320 > ryofslife.com.http-alt: Flags [S], cksum 0xaed7 (correct), seq 1804289383, win 65535, length 0 ... 15:18:18.550721 IP (tos 0x48, ttl 233, id 130, offset 0, flags [none], proto TCP (6), length 40) p9209152-ipngn9901marunouchi.tokyo.ocn.ne.jp.60320 > ryofslife.com.http-alt: Flags [.], cksum 0xad84 (correct), seq 1804289384, ack 3543150099, win 65535, length 0 ... 15:18:18.554528 IP (tos 0x48, ttl 233, id 131, offset 0, flags [none], proto TCP (6), length 120) p9209152-ipngn9901marunouchi.tokyo.ocn.ne.jp.60320 > ryofslife.com.http-alt: Flags [P.], cksum 0xdb95 (correct), seq 0:80, ack 1, win 65535, length 80: HTTP, length: 80 GET / HTTP/1.1 ... 15:18:18.679744 IP (tos 0x48, ttl 233, id 132, offset 0, flags [none], proto TCP (6), length 40) p9209152-ipngn9901marunouchi.tokyo.ocn.ne.jp.60320 > ryofslife.com.http-alt: Flags [.], cksum 0xad34 (correct), seq 80, ack 48, win 65488, length 0 ... 15:18:18.682063 IP (tos 0x48, ttl 233, id 133, offset 0, flags [none], proto TCP (6), length 40) p9209152-ipngn9901marunouchi.tokyo.ocn.ne.jp.60320 > ryofslife.com.http-alt: Flags [.], cksum 0xad04 (correct), seq 80, ack 49, win 65535, length 0 15:18:18.682646 IP (tos 0x48, ttl 233, id 134, offset 0, flags [none], proto TCP (6), length 40) p9209152-ipngn9901marunouchi.tokyo.ocn.ne.jp.60320 > ryofslife.com.http-alt: Flags [F.], cksum 0xad03 (correct), seq 80, ack 49, win 65535, length 0 15:18:18.683615 IP (tos 0x48, ttl 43, id 54157, offset 0, flags [none], proto TCP (6), length 52) I am thinking of sharing the code on my github once done fixing little bits and pieces😎. Anyways, wish you all have a great week! See in the next post!!

Hi! I have been working on my lab and wanted to share its physical and logical topology. I think I made a huge improvement on the diagram compared to the last one from an aesthetic point of view😎. Here is the logical topology. There are networks connected by BGP and I prepared a local network for each one of them. All the three local networks are reachable from each other as they advertise their local network to their peers. Among the three routers, I installed netem to the VyOS so that I can simulate some of the WAN characteristics like latency and packet loss. And here is the physical setup and topology of my lab. I used two L2 switches to connect three routers and to prepare a local network for each of the routers. I recently took a simple benchmark regarding bandwidth and latency using this lab setup. It's great have an environment where you can gets your hands dirty😏. See you in the next post!

Hi! I've been running out of cables for my lab and I decided to make one by myself from a 15m CAT 6 ethernet cable which I got from my local store for about $10. I had to make 4 attempts to finally get a working cable and here are the mistakes that I made. Hope it helps someone who is trying to do the same thing😅. First attempt, the pin for white/orange wire were not properly attached. It is also not looking good as the cable sheet is too short for the plug😂. Second attempt, I misaligned the blue and white/green wire. Third attempt, I realized that I was configuring the order of the wires upside-down respect to the plug🤣🤣🤣. And here is the final product! Mistakes are proof that you are learning😎. See you in the next post!

Hi! I wanted to share that my lab is finally connected to the internet! For the last 6 months ever since I got my first switch and router, my lab never had gotten out of its LAN😅. It's the first time getting out of my LAN and interacting with the internet and I'm just sooo excited about it. The reason I decided to extend my lab to the internet is because I have been looking into technologies used over the internet, TOR in particular. I'm learning how relays used in TOR allows clients to hide their identity over the internet and how it helps people in some countries with strict censorship. I found the technology as well as the role it plays in society very interesting. I believe such technology to ensure people have access to learn what is happening around the world is crucial. Having such tool gives us additional choice in what we choose from the pool of sources and I believe it could make a huge different sometimes. I am learning that there are many ways that I can take part in the community and I'm sure there is something that I can do to help people out there! https://www.torproject.org/ By the way, I noticed that my lab topology is getting pretty messy😂. I'm currently working on BGP and I'll share a nicer topology here once I'm done with all the BGP configurations that I have in my mind. See you in the next post!!!!!

Hi! I have been working on l2tp on my lab and I wanted to leave a tip here as it took me about a week to finally make it work. I'm not sure if the problem that I faced is specific to the device that I am using, namely cisco 892 router, but here is the tip for those working on l2tp. When you are setting the interface which is used for tunneling the LAN, the one you apply "xconnect", it has to be a WAN interface! I found this very weird and confusing. Why would you want to use WAN interface for tunneling LAN interface🤣. The below link really saved me as the given answer was exactly the one I needed. Without it, I'm probably still working wondering why ping is not working even though that the tunnel is established and everything seems configured correctly. Cisco892で, "WANポート"を使わなければL2TP接続した両端の機器間でPing疎通できない I also used a lot of Switched Port Analyzer(SPAN) for debugging. It's very useful and fun tool for labbing! Below is the topology of my lab after setting up l2tp. I have been interested in benchmarking my networking devices for a while and I am hoping to make a post about it within a next couple week. Anyways, see you in the next post!

Hi! I have been working on my home lab for about 2 weeks and I wanted to share how it is going so far! I am trying to add as many things as possible that I learned on networking over the past 3 or 4 months. The topology is getting little messy but I'm thinking of organizing them once I'm done trying out all the things that I have in my mind😅. Below is the topology at the time of this post. And here are some of the info on the hardwares that appear on the topology. R1&R2: Cisco 892 VyOS: DELL Optiplex 3020 L3-1&L3-2: Catalyst 3560 L2-1&L2-2: Catalyst 2960 I'll be posting updates on my home lab whenever I learned anything interesting while working on it🧐. See you in the next post!

Hi! Today, I wanted to share that I installed VyOS on my DELL desktop as I needed additional router for my home lab. I usually install this kind of softwares on Ras Pi but I learned that there is no ARM64 version of VyOS😂. The reason I turned my DELL into VyOS is only because I wanted to try out BGP with physical devices😏. See you in the next post!

Hi! Today, I wanted to share about the things that I have learned by tunneling between Ras Pi and a router through GRE. At first, I was trying GRE on packet tracer but it didn't work for some reason. So I decided to instead work on physical devices which were available at the moment. I will share some of key commands for setting up GRE on Ras Pi. For the router, you will find many resources online for setting up GRE on a cisco router😅. ┌──(kali㉿kali-raspberry-pi)-[~] └─$ sudo ip tunnel add gre1 mode gre remote 172.168.10.25 local 192.168.233.204 ttl 255 ┌──(kali㉿kali-raspberry-pi)-[~] └─$ ip tunnel list gre0: gre/ip remote any local any ttl inherit nopmtudisc gre1: gre/ip remote 172.168.10.25 local 192.168.233.204 ttl 255 ┌──(kali㉿kali-raspberry-pi)-[~] └─$ sudo ip addr add 10.10.10.1/24 dev gre1 ┌──(kali㉿kali-raspberry-pi)-[~] └─$ sudo ip link set gre1 up ┌──(kali㉿kali-raspberry-pi)-[~] └─$ sudo ip addr add 192.168.233.204/24 dev eth0 The process of setting up GRE is the same for both Ras Pi and a router, only difference is the commands😎. Once done with the above set up, you have to configure the route for both the physical interface connected to the router and the virtual tunnel interface. Below is the route table. ┌──(kali㉿kali-raspberry-pi)-[~] └─$ sudo ip route default via 192.168.85.77 dev wlan0 proto dhcp src 192.168.85.76 metric 600 10.10.10.0/24 dev gre1 proto kernel scope link src 10.10.10.1 172.168.10.25 dev eth0 scope link 192.168.85.0/24 dev wlan0 proto kernel scope link src 192.168.85.76 metric 600 192.168.233.0/24 dev eth0 proto kernel scope link src 192.168.233.204 Here 10.10.10.0/24 is the network for the tunnel and 172.168.10.25 is the address of the router's physical interface connected to Ras Pi. When I was working on tunneling yesterday, I couldn't figure out why ping was failing after setting up the tunnel. It was the route info that was missing🤣. See you in the next post!

Hi! Today, I wanted to share that I recently turned my raspberry pi into to a firewall to make it part of my home lab. Here are some notes for setting up IPFire on raspberry pi. When I was setting up IPFire, I got stuck for a little while with a rainbow screen when trying to boot it up. 1. Set "hdmi_safe" to 0 which you will find in config.txt. hdmi_safe=0 2. Set "SERIAL-CONSOLE" to OFF which you will find in uENV.txt. SERIAL-CONSOLE=OFF Hope it helps if any one of you encounters the same issue. Firewall is something that I haven't really looked into and excited about adding new component into my home lab and learning what it is capable of!

Hi! Today, I configured an EtherChannel to see how it affects STP. For the setup, I prepared two switches (Switch1 & Swtich2) and connected them with 2 cables. Below shows how STP is configured on Switch1 before EtherChannel is ready on Switch2. Switch1(config)# Switch1(config)#interface range fastEthernet 0/1-2 Switch1(config-if-range)#channel-group 1 mode active //Swtich1はactiveに設定 Creating a port-channel interface Port-channel 1 Switch1(config-if-range)# Switch1(config-if-range)#channel-protocol LACP Switch1(config-if-range)#exit Switch1(config)#exit Switch1#show 00:11:48: %SYS-5-CONFIG_I: Configured from console by console % Type "show ?" for a list of subcommands Switch1#show etherchannel summary Flags: D - down P - in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use f - failed to allocate aggregator u - unsuitable for bundling w - waiting to be aggregated d - default port Number of channel-groups in use: 1 Number of aggregators: 1 Group Port-channel Protocol Ports ------+-------------+-----------+----------------------------------------------- 1 Po1(SD) LACP Fa0/1(I) Fa0/2(I) Switch1# Switch1#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address ec30.918e.c100 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address ec30.918e.c100 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Fa0/1 Desg FWD 19 128.1 P2p Fa0/2 Desg FWD 19 128.2 P2p As you can see from the above, since the EtherChannel is still not configured on Switch2, you can see that STP recognizes 2 ports as they are not yet bundled even though the 2 ports are registered on the channel-group 1. Below is how Switch2 is configured after setting up Switch. Switch1# Switch1#show etherchannel summary Flags: D - down P - in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use f - failed to allocate aggregator u - unsuitable for bundling w - waiting to be aggregated d - default port Number of channel-groups in use: 1 Number of aggregators: 1 Group Port-channel Protocol Ports ------+-------------+-----------+----------------------------------------------- 1 Po1(SU) LACP Fa0/1(P) Fa0/2(P) Switch1#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address ec30.918e.c100 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address ec30.918e.c100 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Po1 Desg FWD 12 128.56 P2p After the ports are bundled, you can see that there are only 1 port recognized by STP. Another observation you can make is that the cost of the bundle port has decreased from 19 to 12. I also tested how STP will behave if I plugged out one of the port used by the channel-group. Switch1#show etherchannel summary Flags: D - down P - in port-channel I - stand-alone s - suspended H - Hot-standby (LACP only) R - Layer3 S - Layer2 U - in use f - failed to allocate aggregator u - unsuitable for bundling w - waiting to be aggregated d - default port Number of channel-groups in use: 1 Number of aggregators: 1 Group Port-channel Protocol Ports ------+-------------+-----------+----------------------------------------------- 1 Po1(SU) LACP Fa0/1(P) Fa0/2(D) Switch1#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address ec30.918e.c100 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address ec30.918e.c100 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Po1 Desg FWD 19 128.56 P2p Comparing before and after plugging one of the port on Switch1 shows that the cost has decreased but it is still recognized as a port-channel.

Hi! Today, I tested STP with my two switches by simply connecting them with two cables. As shown below, one of the links belonging to the non-root bridge got blocked based on the priority number. pi#show spanning-tree vlan 1 VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address ec30.918e.c100 Cost 19 Port 5 (FastEthernet0/3) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address f029.2952.8d80 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Fa0/1 Desg FWD 19 128.3 P2p Fa0/3 Root FWD 19 128.5 P2p Fa0/5 Altn BLK 19 128.7 P2p As the above shows, Fa0/3 is the root port connected to the switch on the other end. So I plugged it out to see if the connection remains up by changing the root port to Fa0/5. Below is the result. pi>show spanning-tree vlan 1 VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address ec30.918e.c100 Cost 19 Port 7 (FastEthernet0/5) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address f029.2952.8d80 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15 sec Interface Role Sts Cost Prio.Nbr Type ------------------- ---- --- --------- -------- -------------------------------- Fa0/1 Desg FWD 19 128.3 P2p Fa0/5 Root LIS 19 128.7 P2p As expected, Fa0/5 is now the root port and the connection is still up! However, one drawback of this configuration is that one of the links is left unused. In order to utilize both of the links, I can set up an etherchannel and bundle the two links. I'm currently studying etherchannel to actually test it out and see how it differs from simply connected redundant links🧐.

Hi! Today, I was working on Inter VLAN Routing using a router(800) and L2 switch(Catalyst 2960). I connected a PC to each VLAN(VLAN10, VLAN20) and tested if I can ping to each other. Below is the set up for the PCs(Windows, Raspberry Pi) connected to the switch. The ip address for the Windows PC is 192.168.1.2/24 and the gateway address for 192.168.2.0/24 is 192.168.1.1/24. For Raspberry Pi, its ip address is 192.168.2.2/24 and the gateway address for 192.168.1.0/24 is 192.168.2.1/24. C:\WINDOWS\system32>route add 192.168.2.0 mask 255.255.255.0 192.168.1.1 OK! ┌──(kali㉿kali-raspberry-pi)-[~] └─$ sudo ifconfig eth0 192.168.2.2 ┌──(kali㉿kali-raspberry-pi)-[~] └─$ sudo ip route add 192.168.1.0/255.255.255.0 via 192.168.2.1 dev eth0 onlink ┌──(kali㉿kali-raspberry-pi)-[~] └─$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.164.146 0.0.0.0 UG 600 0 0 wlan0 192.168.1.0 192.168.2.1 255.255.255.0 UG 0 0 0 eth0 192.168.2.0 192.168.2.1 255.255.255.0 UG 0 0 0 eth0 192.168.164.0 0.0.0.0 255.255.255.0 U 600 0 0 wlan0 Then I configured the switch. I prepared vlan10 & vlan20 for the Windows PC & Raspberry Pi, respectively. After finishing setting up vlans, you need to assign ports to the respective vlans. This time, I used 4 cables, two for connecting the PCs to the switch and the other two for connecting the router. Here are the commands I used for creating vlans. Switch>enable Switch#config terminal Enter configuration commands, one per line. End with CNTL/Z. Switch(config)#vlan 10 Switch(config-vlan)#vlan 20 Switch(config-vlan)#do show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4 Fa0/5, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10, Fa0/11, Fa0/12 Fa0/13, Fa0/14, Fa0/15, Fa0/16 Fa0/17, Fa0/18, Fa0/19, Fa0/20 Fa0/21, Fa0/22, Fa0/23, Fa0/24 Gi0/1, Gi0/2 10 VLAN0010 active 20 VLAN0020 active 1002 fddi-default act/unsup 1003 token-ring-default act/unsup 1004 fddinet-default act/unsup 1005 trnet-default act/unsup Next I assigned the ports to the respective vlans. Switch(config)#do show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4 Fa0/5, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10, Fa0/11, Fa0/12 Fa0/13, Fa0/14, Fa0/15, Fa0/16 Fa0/17, Fa0/18, Fa0/19, Fa0/20 Fa0/21, Fa0/22, Fa0/23, Fa0/24 Gi0/1, Gi0/2 10 VLAN0010 active 20 VLAN0020 active 1002 fddi-default act/unsup 1003 token-ring-default act/unsup 1004 fddinet-default act/unsup 1005 trnet-default act/unsup VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2 ---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------ 1 enet 100001 1500 - - - - - 0 0 10 enet 100010 1500 - - - - - 0 0 20 enet 100020 1500 - - - - - 0 0 1002 fddi 101002 1500 - - - - - 0 0 Switch(config)#interface fa0/1 Switch(config-if)# 00:02:41: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/3 (1), with Router FastEthernet0 (10). Switch(config-if)# 00:02:47: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/5 (1), with Router FastEthernet1 (20). Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 10 Switch(config-if)#interface fa0/2 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 20 Switch(config-if)# 00:03:36: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/3 (1), with Router FastEthernet0 (10). Switch(config-if)#interface fa0/3 Switch(config-if)#switchport access vlan 20 00:03:42: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/5 (1), with Router FastEthernet1 (20). Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 10 Switch(config-if)#interface fa0/5 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 20 Switch(config-if)#switchport access vlan 20 00:04:10: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state tmode access Switch(config-if)#do show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/4, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10, Fa0/11, Fa0/12 Fa0/13, Fa0/14, Fa0/15, Fa0/16 Fa0/17, Fa0/18, Fa0/19, Fa0/20 Fa0/21, Fa0/22, Fa0/23, Fa0/24 Gi0/1, Gi0/2 10 VLAN0010 active Fa0/1, Fa0/3 20 VLAN0020 active Fa0/2, Fa0/5 1002 fddi-default act/unsup 1003 token-ring-default act/unsup 1004 fddinet-default act/unsup 1005 trnet-default act/unsup VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2 ---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------ 1 enet 100001 1500 - - - - - 0 0 10 enet 100010 1500 - - - - - 0 0 20 enet 100020 1500 - - - - - 0 0 1002 fddi 101002 1500 - - - - - 0 0 1003 tr 101003 1500 - - - - - 0 0 After working on the switch, I had to configure the ports on the router each connected to the switch's vlan port. At first, I tried to assign IP address to the ports directly but I got this error. Router#config terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface fastethernet0 Router(config-if)#ip address 192.168.1.1 255.255.255.0 % IP addresses may not be configured on L2 links. The problem was that the port which I was configuring only works with L2 layer and an IP address can't be assigned. After doing some research, I figured out that I need to first create a vlan so that I can assign an IP address to it. The created vlan with an IP address can then be assigned to a port of your choice. Here is how I did it. Router(config)#vlan 10 Router(config-vlan)#vlan 20 Router(config-vlan)#interface vlan 10 Router(config-if)#ip address 192.168.1.1 255.255.255.0 % 192.168.1.0 overlaps with Vlan1 Router(config-if)#interface vlan 1 Router(config-if)#ip address 192.168.3.1 255.255.255.0 Router(config-if)#interface vlan 10 Router(config-if)#ip address 192.168.1.1 255.255.255.0 Router(config-if)#no shut Router(config-if)#interface vlan 20 Router(config-if)# *Jan 3 09:40:49.434: %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan20, changed state to down Router(config-if)#ip address 192.168.2.1 255.255.255.0 % 192.168.2.0 overlaps with Vlan2 Router(config-if)#interface vlan 2 Router(config-if)#ip address 192.168.4.1 255.255.255.0 Router(config-if)#interface vlan 20 Router(config-if)#ip address 192.168.2.1 255.255.255.0 Router(config-if)#no shut Router(config-if)#interface fastethernet 1 Router(config-if)#switchport access vlan 10 Router(config-if)#interface fastethernet 2 Router(config-if)#switchport access vlan 20 Router(config-if)#exit Router(config)# Router(config)#do show interface (| include Vlan) ... Vlan10 is up, line protocol is up Hardware is EtherSVI, address is e4d3.f166.3fd2 (bia e4d3.f166.3fd2) Internet address is 192.168.1.1/24 MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 ... Vlan20 is up, line protocol is up Hardware is EtherSVI, address is e4d3.f166.3fd2 (bia e4d3.f166.3fd2) Internet address is 192.168.2.1/24 MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec, reliability 255/255, txload 1/255, rxload 1/255 ... Below is the routing table after configuring the router. Router>show ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP + - replicated route, % - next hop override Gateway of last resort is not set 192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.1.0/24 is directly connected, Vlan10 L 192.168.1.1/32 is directly connected, Vlan10 192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks C 192.168.2.0/24 is directly connected, Vlan20 L 192.168.2.1/32 is directly connected, Vlan20 Now we are ready to ping the PC on the other VLAN connected by the router! Here is the result pinging from the Windows PC(192.168.1.2/24) to Raspberry Pi(192.168.2.2/24) C:\Users\Ryo>ping 192.168.2.2 Pinging 192.168.2.2 with 32 bytes of data: Reply from 192.168.2.2: bytes=32 time=1ms TTL=63 Reply from 192.168.2.2: bytes=32 time=11ms TTL=63 Reply from 192.168.2.2: bytes=32 time=1ms TTL=63 Reply from 192.168.2.2: bytes=32 time=1ms TTL=63 Ping statistics for 192.168.2.2: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 1ms, Maximum = 11ms, Average = 3ms Configuring the router was somewhat difficult as the commands I found online for inter VLAN routing didn't work for the router(800). I had to do some researching to find the commands that works for the router but it was fun as you don't get to do this kind of researching when you are working on packet tracer😎.

I recently bought a router and 2 switches(L2 and L3) for a studying purpose. Today I tried one of the switches, Catalyst 2960. I connected two of my PC and see if I can ping from one to the other. After connecting two of my PC to the ports Fa0/1-2, I checked if they are really connected. Switch>show mac address-table Mac Address Table ------------------------------------------- Vlan Mac Address Type Ports ---- ----------- -------- ----- All 0100.0ccc.cccc STATIC CPU All 0100.0ccc.cccd STATIC CPU All 0180.c200.0000 STATIC CPU All 0180.c200.0001 STATIC CPU All 0180.c200.0002 STATIC CPU All 0180.c200.0003 STATIC CPU All 0180.c200.0004 STATIC CPU All 0180.c200.0005 STATIC CPU All 0180.c200.0006 STATIC CPU All 0180.c200.0007 STATIC CPU All 0180.c200.0008 STATIC CPU All 0180.c200.0009 STATIC CPU All 0180.c200.000a STATIC CPU All 0180.c200.000b STATIC CPU All 0180.c200.000c STATIC CPU All 0180.c200.000d STATIC CPU All 0180.c200.000e STATIC CPU All 0180.c200.000f STATIC CPU All 0180.c200.0010 STATIC CPU All ffff.ffff.ffff STATIC CPU 1 902e.169d.b2f1 DYNAMIC Fa0/1 1 e45f.01d3.5bd9 DYNAMIC Fa0/2 Total Mac Addresses for this criterion: 22 You can see the mac address table has the mac address of the each device connected to the port(Fa0/1-2). However, I wasn't able to ping from my Windows PC(Fa0/1) to Raspberry-pi(Fa0/2). I checked the ARP table of my Windows PC and it showed the list with the mac address of raspberry pi. C:\>arp -a Interface: 192.168.1.2 --- 0x11 Internet Address Physical Address Type 192.168.1.3 e4-5f-01-d3-5b-d9 dynamic 192.168.1.255 ff-ff-ff-ff-ff-ff static The problem was my Windows PC's firewall😅. After configuring its firewall rules to allow ICMP traffic, I was able to ping! C:\Users\Ryo>ping 192.168.1.3 Pinging 192.168.1.3 with 32 bytes of data: Reply from 192.168.1.3: bytes=32 time=2ms TTL=64 Reply from 192.168.1.3: bytes=32 time=6ms TTL=64 Reply from 192.168.1.3: bytes=32 time=1ms TTL=64 Reply from 192.168.1.3: bytes=32 time<1ms TTL=64 Ping statistics for 192.168.1.3: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 6ms, Average = 2ms

I tried to understand the difference between VLAN and subnet by looking into their ARP broadcast request. First I deleted all the ARP entries on the source PC so that when I ping, there will be an ARP request broadcasted to all the devices connected to the switch. Here is how you can check and delete the ARP table. C:\>arp -a Internet Address Physical Address Type 192.168.2.4 0001.436a.8be5 dynamic C:\>arp -d C:\>arp -a No ARP Entries Found After deleting all the ARP entries, the source PC will send an ARP request as it has no mac address on its table. Here is the list of ports on the switch when an ARP request was sent. It shows an ARP reqeust is sent to all the ports except the one(FastEthernet0/3) which is connected to the source PC. In addition, even though FastEthernet0/1-2 are not within the same subnet(192.168.2.0/24), you can see that they still receive the ARP request sent by the source PC(192.168.2.2/24). 1. FastEthernet0/1 sends out the frame. #192.168.1.2 2. FastEthernet0/2 sends out the frame. #192.168.1.3 3. FastEthernet0/4 sends out the frame. #192.168.2.3 4. FastEthernet0/5 sends out the frame. #192.168.2.4 Now its time see how an ARP request will behave when the switch is divided into VLANs(192.168.1.0/24, 192.168.2.0/24) . I once again deleted all the ARP entries in the table of the source PC and here is the commands I used for creating VLANs. Switch>enable Switch#config terminal Enter configuration commands, one per line. End with CNTL/Z. Switch(config)#int fa0/1 Switch(config-if)#exit Switch(config)#vlan 10 Switch(config-vlan)#vlan 20 Switch(config-vlan)#int fa0/1 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 10 Switch(config-if)#int fa0/2 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 10 Switch(config-if)#int fa0/3 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 20 Switch(config-if)#int fa0/4 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 20 Switch(config-if)#int fa0/5 Switch(config-if)#switchport mode access Switch(config-if)#switchport access vlan 20 Switch(config-if)#do show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/6, Fa0/7, Fa0/8, Fa0/9 Fa0/10, Fa0/11, Fa0/12, Fa0/13 Fa0/14, Fa0/15, Fa0/16, Fa0/17 Fa0/18, Fa0/19, Fa0/20, Fa0/21 Fa0/22, Fa0/23, Fa0/24, Gig0/1 Gig0/2 10 vlan01 active Fa0/1, Fa0/2 20 vlan02 active Fa0/3, Fa0/4, Fa0/5 1002 fddi-default active 1003 token-ring-default active 1004 fddinet-default active 1005 trnet-default active I created VLAN01 and VLAN02 for 192.168.1.0/24 and 192.168.2.0/24, respectively. And here is the list of the ports that received an ARP request sent by the source PC(192.168.2.2/24). It shows that FastEthernet0/1-2 are not receiving an ARP request any more as they no longer belong to the same VLAN as the source PC(VLAN02)! 1. FastEthernet0/4 sends out the frame. #VLAN01 2. FastEthernet0/5 sends out the frame. #VLAN02 Once you are done with the VLANs, you can place the ports back to the default VLAN by the below commands. Switch(config-if-range)#interface range Fa 0/1-5 Switch(config-if-range)#switchport access vlan 1 Switch(config-if-range)#do show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4 Fa0/5, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10, Fa0/11, Fa0/12 Fa0/13, Fa0/14, Fa0/15, Fa0/16 Fa0/17, Fa0/18, Fa0/19, Fa0/20 Fa0/21, Fa0/22, Fa0/23, Fa0/24 Gig0/1, Gig0/2 10 vlan01 active 20 vlan02 active 1002 fddi-default active 1003 token-ring-default active 1004 fddinet-default active 1005 trnet-default active Switch(config-if-range)#no vlan 10 Switch(config-if-range)#no vlan 20

After studying how different devices work at different layers, I got little confused how ping works if its only given ip address to reach the destination pc connected via switch which is a layer 2 device. Here's how it works. 1. We only have the destination's ip and no mac address info. ->ARP request which is broadcasted to all devices connected to the switch. 2. Once your PC has the mac address in its mac address table, the frame is sent to the switch which contains the mac address of the destination pc. 3. Switch needs to know which port is connected to the PC with the destination mac address. ->Flood the frame to all other ports if the destination mac address is not in the mac address table. 4. Once the switch gets the reply form the destination PC, it now knows which port to send the frame to get to the destination PC! Here are ARP and Mac address tables before and after ping. Switch#show mac address-table Mac Address Table ------------------------------------------- Vlan Mac Address Type Ports ---- ----------- -------- ----- Switch#show mac address-table Mac Address Table ------------------------------------------- Vlan Mac Address Type Ports ---- ----------- -------- ----- 1 00e0.8fe3.e0b3 DYNAMIC Fa0/2 1 00e0.f7a1.365d DYNAMIC Fa0/1 C:\>arp -a No ARP Entries Found C:\>arp -a Internet Address Physical Address Type 192.168.1.2 00e0.8fe3.e0b3 dynamic

For testing static routes, I created a system with 2 routers each connected to a PC. There are 3 networks so that one PC can connect to the other after setting up a static route. Here I first configured router's interface for 192.168.1.0/24 and 192.168.1.1/24 is the default gateway for 192.168.1.0/24. I did the same for the other router responsible for 192.168.2.0/24. The third network(192.168.3.0/24) which needs to be configured is the one connecting the two routers. Router>enable Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface GigabitEthernet 0/0/0 Router(config-if)#ip address 192.168.1.1 255.255.255.0 Router(config-if)#no shutdown Router(config-if)# %LINK-5-CHANGED: Interface GigabitEthernet0/0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/0, changed state to up Router(config-if)#do show interfaces GigabitEthernet0/0/0 is up, line protocol is up (connected) Hardware is ISR4331-3x1GE, address is 0001.4384.9c01 (bia 0001.4384.9c01) Internet address is 192.168.1.1/24 ... After setting up all three networks, I pinged form the PC with 192.168.1.2/24. But the result shows that it is still not reachable. C:\>ping 192.168.2.2 Pinging 192.168.2.2 with 32 bytes of data: Reply from 192.168.1.1: Destination host unreachable. Reply from 192.168.1.1: Destination host unreachable. Reply from 192.168.1.1: Destination host unreachable. Reply from 192.168.1.1: Destination host unreachable. Ping statistics for 192.168.2.2: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), The remaining task is to set up the static routes so that the packet can reach the PC with 192.168.2.2/24. Here is how I set up the static route for 192.168.2.2/24. Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.3.2 After setting up as above, you still won't be able to get replies from the other end as the returning packets get lost at the 192.168.3.2/24. C:\>ping 192.168.2.2 Pinging 192.168.2.2 with 32 bytes of data: Request timed out. Request timed out. Request timed out. Request timed out. Ping statistics for 192.168.2.2: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), Once I set up the static route as below, I was able to get replies from 192.168.2.2/24! Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.3.1 C:\>ping 192.168.2.2 Pinging 192.168.2.2 with 32 bytes of data: Reply from 192.168.2.2: bytes=32 time<1ms TTL=126 Reply from 192.168.2.2: bytes=32 time=10ms TTL=126 Reply from 192.168.2.2: bytes=32 time<1ms TTL=126 Reply from 192.168.2.2: bytes=32 time=11ms TTL=126 Ping statistics for 192.168.2.2: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 11ms, Average = 5ms

I have been studying basic networking by reading books for CCNA. At this point, I think I should go hands-on with packet tracer or the router (Cisco 892) and switches (Cisco L2 and L3) I bought this week for studying purpose. Here are the list of the things I want to try hands-on. ・Static route ・OSPF ・ACL ・DHCP ・Unidirection & Bidirectional NAT ・NAPT(PAT) ・VLAN only using access ports (single switch) ・VLAN using access and trunk ports (two switches) ・VLAN rounting (using router and L2 switch, later using L3 switch)

I started using packet tracer and enjoying the tool a lot. I configured hub, switch, and router based network using the tool. It's really fun to put the materials you learned from books into practice! Here are the commands I used for configuring the router and the details of what it's doing. Router>enable Router# Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface GigabitEthernet0/0 #select the port(interface) on the router Router(config-if)#ip address 192.168.1.4 255.255.255.0 #assign gateway IP address to the interface Router(config-if)#no shutdown #bring up the inerface Router(config-if)# %LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up Here I tested if I am connected to the network configured above by pinging from a node within another network. C:\>ping 192.168.1.3 Pinging 192.168.1.3 with 32 bytes of data: Request timed out. Reply from 192.168.1.3: bytes=32 time=14ms TTL=127 Reply from 192.168.1.3: bytes=32 time<1ms TTL=127 Reply from 192.168.1.3: bytes=32 time=11ms TTL=127 Ping statistics for 192.168.1.3: Packets: Sent = 4, Received = 3, Lost = 1 (25% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 14ms, Average = 8ms It shows that the first packet is dropped. This is because of the switch on the network configured above does not have not have the destination pc's MAC address in its ARP table and need to get the one by 'flooding' which takes some time.

"ip addr" shows the mac address for each interface, it's e4:5f:01:d3:5b:da in the case of wlan0. "arp" shows the router's mac address. ┌──(kali㉿kali-raspberry-pi)-[/var/lib/dhcp] └─$ ip addr ... 3: wlan0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether e4:5f:01:d3:5b:da brd ff:ff:ff:ff:ff:ff inet 192.168.164.76/24 brd 192.168.164.255 scope global dynamic noprefixroute wlan0 valid_lft 2858sec preferred_lft 2858sec inet6 fe80::ed36:b7c6:afa8:838d/64 scope link noprefixroute valid_lft forever preferred_lft forever ┌──(kali㉿kali-raspberry-pi)-[/var/lib/dhcp] └─$ arp Address HWtype HWaddress Flags Mask Iface 192.168.164.146 ether ac:a8:8e:ec:6e:66 C wlan0 The first hop of "traceroute", which is 192.168.164.146, shows the router's local ip address. ┌──(kali㉿kali-raspberry-pi)-[~] └─$ traceroute 8.8.8.8 traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets 1 192.168.164.146 (192.168.164.146) 40.242 ms 41.001 ms 43.085 ms 2 121.83.171.60 (121.83.171.60) 74.412 ms 74.476 ms 76.689 ms 3 100.64.3.181 (100.64.3.181) 81.472 ms 81.503 ms 83.573 ms 4 58.191.128.178 (58.191.128.178) 86.298 ms 85.972 ms 86.346 ms 5 61.205.127.233 (61.205.127.233) 86.192 ms 87.454 ms 87.482 ms 6 203.140.81.209 (203.140.81.209) 86.012 ms 48.984 ms 55.241 ms 7 60.56.20.190 (60.56.20.190) 54.917 ms 54.165 ms 62.331 ms 8 142.250.172.36 (142.250.172.36) 62.152 ms 61.755 ms 65.046 ms 9 * * * 10 dns.google (8.8.8.8) 65.708 ms 65.737 ms 65.926 ms After piging to my laptop within the same local network, my laptop's mac address is added to the arp table. But ping is failing for some reason... ┌──(kali㉿kali-raspberry-pi)-[/var/lib/dhcp] └─$ ping 192.168.164.137 PING 192.168.164.137 (192.168.164.137) 56(84) bytes of data. ^C --- 192.168.164.137 ping statistics --- 7 packets transmitted, 0 received, 100% packet loss, time 6143ms ┌──(kali㉿kali-raspberry-pi)-[/var/lib/dhcp] └─$ arp Address HWtype HWaddress Flags Mask Iface 192.168.164.146 ether ac:a8:8e:ec:6e:66 C wlan0 192.168.164.137 ether 50:c2:e8:29:9b:cb C wlan0 Wireshark shows the arp protocol is requesting the mac address of 192.168.164.137, and the response from the router shows the mac address is 50:c2:e8:29:9b:cb. However there is no response from 192.168.164.76. 2 18.664379309 Raspberr_d3:5b:da Broadcast ARP 42 Who has 192.168.164.137? Tell 192.168.164.76 3 18.680115301 CloudNet_29:9b:cb Raspberr_d3:5b:da ARP 42 192.168.164.137 is at 50:c2:e8:29:9b:cb 4 18.680196856 192.168.164.76 192.168.164.137 ICMP 98 Echo (ping) request id=0x0002, seq=1/256, ttl=64 (no response found!) I checked my laptop's firewall configuration and enable ping echo request. Ping is now working! ┌──(kali㉿kali-raspberry-pi)-[~] └─$ ping 192.168.164.137 PING 192.168.164.137 (192.168.164.137) 56(84) bytes of data. 64 bytes from 192.168.164.137: icmp_seq=1 ttl=128 time=53.2 ms 64 bytes from 192.168.164.137: icmp_seq=2 ttl=128 time=75.9 ms 64 bytes from 192.168.164.137: icmp_seq=3 ttl=128 time=8.42 ms 64 bytes from 192.168.164.137: icmp_seq=4 ttl=128 time=42.1 ms 64 bytes from 192.168.164.137: icmp_seq=5 ttl=128 time=8.71 ms ^C --- 192.168.164.137 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 4006ms rtt min/avg/max/mdev = 8.417/37.644/75.852/26.122 ms

I didn't know there are protocols defining the optimal path for exchanging packets between networks. It's interesting how they use different metrics(hop count, bandwidth, etc) to determine the best path.

I started studying for CCNA hoping to learn basic networking!

Link to my blog. https://illinoisfslife.com/

Here are the commands I used after finishing compiling the source code. ──(kali㉿kali-raspberry-pi)-[~/sources/linux] └─$ ls arch certs CREDITS Documentation fs init ipc Kconfig lib MAINTAINERS mm modules.builtin.modinfo modules.order net README.md scripts sound tools virt vmlinux.o block COPYING crypto drivers include io_uring Kbuild kernel LICENSES Makefile modules.builtin modules-only.symvers Module.symvers README samples security System.map usr vmlinux vmlinux.symvers ┌──(kali㉿kali-raspberry-pi)-[~/sources/linux] └─$ sudo make modules_install ┌──(kali㉿kali-raspberry-pi)-[~/sources/linux] └─$ sudo cp arch/arm64/boot/dts/broadcom/*.dtb /boot/ ┌──(kali㉿kali-raspberry-pi)-[~/sources/linux] └─$ sudo cp arch/arm64/boot/dts/overlays/*.dtb* /boot/overlays/ ┌──(kali㉿kali-raspberry-pi)-[~/sources/linux] └─$ sudo cp arch/arm64/boot/dts/overlays/README /boot/overlays/ ┌──(kali㉿kali-raspberry-pi)-[~/sources/linux] └─$ sudo cp arch/arm64/boot/Image.gz /boot/kernel-ryo-1.img ┌──(kali㉿kali-raspberry-pi)-[/boot] └─$ sudo vim config.txt # 64-bit kernel for Raspberry Pi 4 is called kernel8l (armv8a) kernel=kernel-ryo-1.img ┌──(kali㉿kali-raspberry-pi)-[/boot] └─$ sudo reboot And I got this! ┌──(kali㉿kali-raspberry-pi)-[/var/log] └─$ uname -a Linux kali-raspberry-pi 5.15.83-v8-ryos-first-kernel+ #1 SMP PREEMPT Fri Dec 16 12:25:46 UTC 2022 aarch64 GNU/Linux ┌──(kali㉿kali-raspberry-pi)-[/var/log] └─$ cat messages Dec 16 14:43:01 kali-raspberry-pi pulseaudio[968]: ICE I/O error handler called Dec 16 14:43:04 kali-raspberry-pi kernel: [ 0.000000] Hello World, I'm Ryo! Dec 16 14:43:04 kali-raspberry-pi kernel: [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd083] Dec 16 14:43:04 kali-raspberry-pi kernel: [ 0.000000] Linux version 5.15.83-v8-ryos-first-kernel+ (kali@kali-raspberry-pi) (gcc (Debian 11.3.0-5) 11.3.0, GNU ld (GNU Binutils for Debian) 2.38.90.20220713) #1 SMP PREEMPT Fri Dec 16 12:25:46 UTC 2022 This time I was able to print during the boot up with my customized kernel! I can now try to do some work on the network stack and compile😁.

This time, I modified /arm/arm64/kernel/setup.c as below. You can find the source code here. void __init smp_setup_processor_id(void) { u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK; set_cpu_logical_map(0, mpidr); pr_info("Hello World, its Ryo!"); pr_info("Booting Linux on physical CPU 0x%010lx [0x%08x]\n", (unsigned long)mpidr, read_cpuid_id()); } Here is the commands that I used. $ KERNEL=kernel8 $ make bcm2711_defconfig $ vim .config CONFIG_LOCALVERSION="-v8-ryos-first-kernel" $ make -j4 Image.gz modules dtbs

The packet data received by NIC is held by sk_buff(). I'm curious how packets travels from NIC to user space programs.

It's completed compiling! Here is what I did afterwards. $ make ... OBJCOPY arch/arm64/boot/Image GZIP arch/arm64/boot/Image.gz [1] + done make $ ls arch certs CREDITS Documentation fs init Kbuild kernel LICENSES Makefile modules.builtin modules-only.symvers Module.symvers README scripts sound tools virt vmlinux.o block COPYING crypto drivers include ipc Kconfig lib MAINTAINERS mm modules.builtin.modinfo modules.order net samples security System.map usr vmlinux vmlinux.symvers $ file vmlinux vmlinux: ELF 64-bit LSB pie executable, ARM aarch64, version 1 (SYSV), statically linked, BuildID[sha1]=8d74859bebe9cce14587e1b3272c7b11fe5de611, not stripped $ sudo make modules_install INSTALL /lib/modules/5.15.44-Re4son-v8l/kernel/sound/usb/misc/snd-ua101.ko INSTALL /lib/modules/5.15.44-Re4son-v8l/kernel/sound/usb/snd-usb-audio.ko INSTALL /lib/modules/5.15.44-Re4son-v8l/kernel/sound/usb/snd-usbmidi-lib.ko DEPMOD /lib/modules/5.15.44-Re4son-v8l $ sudo make install sh ./arch/arm64/boot/install.sh 5.15.44-Re4son-v8l \ arch/arm64/boot/Image System.map "/boot" run-parts: executing /etc/kernel/postinst.d/initramfs-tools 5.15.44-Re4son-v8l /boot/vmlinuz-5.15.44-Re4son-v8l update-initramfs: Generating /boot/initrd.img-5.15.44-Re4son-v8l cryptsetup: ERROR: Couldn't resolve device /dev/root cryptsetup: WARNING: Couldn't determine root device I'm having trouble installing compiled files. I did some research and boot up process is not what I thought as Rasbarry Pi does not support grub😰. I found the kernel source code for Raspberry Pi here. Another mistake that I found is that I was working on linux/arch/arm. My Raspberry Pi is 64bits machine so the directory should be under linux/arch/arm64. Glad I found this mistake before compilation. I will once again compile the source code and see how it goes😂.

Some stuff I learned about how Nmap SYN scanning works. Below is the captured packets from Wireshark. 10 13.006851 192.168.100.103 192.168.100.101 TCP 60 44276 → 445 [SYN] Seq=0 Win=1024 Len=0 MSS=1460 15 13.007423 192.168.100.101 192.168.100.103 TCP 60 445 → 44276 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1460 16 13.007594 192.168.100.103 192.168.100.101 TCP 60 44276 → 445 [RST] Seq=1 Win=0 Len=0 It shows that the the state of port is open as the server's reply to the nmap's SYN is SYN,ACK. You can observe that SYN scan terminates 3 way handshake by RST sent by nmap. Also, here is the source code I found which I thought might be useful for spoofing Nmap OS detection. You can find the source code here. I think the below code is the part where it specifies the window size of a packet. /* Numbers are taken from RFC3390. * * John Heffner states: * * The RFC specifies a window of no more than 4380 bytes * unless 2*MSS > 4380. Reading the pseudocode in the RFC * is a bit misleading because they use a clamp at 4380 bytes * rather than use a multiplier in the relevant range. */ __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) { __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); if (!cwnd) { if (tp->mss_cache > 1460) cwnd = 2; else cwnd = (tp->mss_cache > 1095) ? 3 : 4; } return min_t(__u32, cwnd, tp->snd_cwnd_clamp); }

I modified ./arch/arm/kernel/setup.c as below. You can find the source code here. void __init smp_setup_processor_id(void) { int i; u32 mpidr = is_smp() ? read_cpuid_mpidr() & MPIDR_HWID_BITMASK : 0; u32 cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0); cpu_logical_map(0) = cpu; for (i = 1; i < nr_cpu_ids; ++i) cpu_logical_map(i) = i == cpu ? 0 : i; /* * clear __my_cpu_offset on boot CPU to avoid hang caused by * using percpu variable early, for example, lockdep will * access percpu variable inside lock_release */ set_my_cpu_offset(0); pr_info("Hello world, this is Ryo speaking!\n"); pr_info("Booting Linux on physical CPU 0x%x\n", mpidr); } After the above modification, I started compiling the source code as below. $ cp /boot/config-$(uname -r) .config $ sudo apt-get install git fakeroot build-essential ncurses-dev xz-utils libssl-dev bc flex libelf-dev bison $ make menuconfig No change to .config *** End of the configuration. *** Execute 'make' to start the build or try 'make help'. $ make This is going to take a while😝.

I learned that you can't use printk() during the early stage of the boot up process😅. Here is the output of /var/log/messages. ┌──(kali㉿kali-raspberry-pi)-[/var/log] └─$ cat messages Dec 11 02:00:25 kali-raspberry-pi rsyslogd: [origin software="rsyslogd" swVersion="8.2206.0" x-pid="525" x-info="https://www.rsyslog.com"] rsyslogd was HUPed Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd083] Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] Linux version 5.15.44-Re4son-v8l+ (root@kali-raspberry-pi) (gcc (Debian 11.2.0-19) 11.2.0, GNU ld (GNU Binutils for Debian) 2.38) #1 SMP PREEMPT Debian kali-pi (2022-07-03) Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] random: crng init done Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] Machine model: Raspberry Pi 4 Model B Rev 1.5 I once again gone through the source code and found that "Booting Linux on" is printed by pr_info() and Linux version 5.15.44-Re4son-v8l+ is printed by decompressor_printk(). I will go for pr_info() as it comes earlier than decompressor_printk()😝. ┌──(kali㉿kali-raspberry-pi)-[~/sources/linux-5.15.44] └─$ grep -r "Booting" . ./arch/arm/kernel/setup.c: pr_info("Booting Linux on physical CPU 0x%x\n", mpidr); ┌──(kali㉿kali-raspberry-pi)-[~/sources/linux-5.15.44] └─$ grep printk * -r | grep "decompressor_printk" arch/s390/boot/pgm_check_info.c: decompressor_printk("Linux version %s\n", kernel_version);

I check my Raspberry Pi kernel version and its 5.15.44. $ uname -r 5.15.44-Re4son-v8l+ I want to printk during the boot up process so I look through the kernel source code where "Booting Linux on..." is printed as shown below. ┌──(kali㉿kali-raspberry-pi)-[/var/log] └─$ cat messages Dec 11 02:00:25 kali-raspberry-pi rsyslogd: [origin software="rsyslogd" swVersion="8.2206.0" x-pid="525" x-info="https://www.rsyslog.com"] rsyslogd was HUPed Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd083] Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] Linux version 5.15.44-Re4son-v8l+ (root@kali-raspberry-pi) (gcc (Debian 11.2.0-19) 11.2.0, GNU ld (GNU Binutils for Debian) 2.38) #1 SMP PREEMPT Debian kali-pi (2022-07-03) Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] random: crng init done Dec 11 02:27:19 kali-raspberry-pi kernel: [ 0.000000] Machine model: Raspberry Pi 4 Model B Rev 1.5 Seems like "Booting Linux on..." is printed by pr_info(), not printk(). Not yet sure where the first printk() is... You can find the source code for version 5.15.44 here.

Today I inserted a kernel module which simply prints "Hello Ryo!" under /var/log/messages. Here is the c program. int init_module(void) { //printk(KERN_INFO "Hello world 1.\n"); printk(KERN_INFO "Hello Ryo!\n"); return 0; } void cleanup_module(void) { //printk(KERN_INFO "Goodbye world 1.\n"); printk(KERN_INFO "Bye Ryo!\n"); } MODULE_LICENSE("GPL"); initi_module() is used to initialize the module and cleanup_module is responsible for shutting down the module. When you are using printk(), you can give eight 8 levels of different logs at the part of "KERN_INFO". Below is the commands I used for initializing and removing the kernel. make -C /lib/modules/`uname -r`/build/ M=${PWD} modules sudo insmod hello_world.ko sudo rmmod hello_world.ko Here is the output of the above operation. Dec 12 14:21:27 kali-raspberry-pi kernel: [ 8233.939103] Hello Ryo! Dec 12 14:22:33 kali-raspberry-pi kernel: [ 8299.742310] Bye Ryo! I will start looking into where I can printk() inside the kernel source code during the boot up process!

I've been working on TUN device for a while and thought I should look into how packets are handled within the kernel. TUN device allows us to handle packets above layer 3. The corresponding entry point within the kernel is ip_rcv() whih can be found here. ip_local_deliver_finish() is the function whichis the exit of the layer 3 responsible for passing data to the layer 4 stack based on the protocol found in the ip header. You can find the function https://elixir.bootlin.com/linux/v2.6.20/source/net/ipv4/ip_input.c#L199. After ip_local_deliver_finish(), the data is sent to the function handling layer 4 protocol such as tcp_v4_rcv(), udp_rcv(), icmp_rcv(). Might be fun to customize your own network stack and make a kernel of your own😝.

I am getting used to reading the hexs shown in Wireshark. Here is the summary of what is going with the below packet sent by my TUN program. 0x00, 0x00, 0x08, 0x00, 0x45, 0x00, 0x00, 0x54, 0x89, 0x4b, 0x40, 0x00, 0x40, 0x01, 0x39, 0x59, 0xcb, 0x00, 0x71, 0x02, 0xcb, 0x00, 0x71, 0x01, 0x08, 0x00, 0x2a, 0xc7, 0x00, 0x19, 0x00, 0x07, 0xc8, 0xb6, 0x8c, 0x63, 0x00, 0x00, 0x00, 0x00, 0xaf, 0x2b, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37 The first 4 bit (4 of 0x45) ・Version: the fist field tells us which IP version we are using, only IPv4 uses this header so you will always find decimal value 4 here. The first 4 bit (5 of 0x45) ・The length of the ip header. In the case of this example, 5=>5*4(bytes)=>20(bytes)=>20 pair(0x45)s, as each hex is 4 bits. ・Because of the maximum possible value f=>15, the maximum ip header length is 15*4byte=60byte. Protocol: 0x01 ・1 stands for ICMP, 6 stands for tcp, 17 stands for UDP Source and destination address: 0xcb, 0x00, 0x71, 0x02, 0xcb, 0x00, 0x71, 0x01 ・In decimal, 203.0.113.2 and 203.0.113.1 respectively.

Below is the c program for sending receiving packets using TUN device. You should comment out either the dump_packet() or send_packet(). Otherwise, the program will be sending and receiving packets of its own. void dump_packet(int fd, int count, char* buffer) { printf("the fd is %d. read %d bytes!\n", fd, count); int i; for (i=0; i IFNAMSIZ) { return 1; } // Request a TUN device: int fd = open("/dev/net/tun", O_RDWR); if (fd == -1) { return 1; } struct ifreq ifr; memset(&ifr, 0, sizeof(ifr)); ifr.ifr_flags = IFF_TUN; strncpy(ifr.ifr_name, device_name, IFNAMSIZ); int res = ioctl(fd, TUNSETIFF, &ifr); if (res == -1) { return 1; } printf("hello world\n"); //char buffer[BUFFLEN]; char *dumpbuffer = (char *) calloc(300, sizeof(char)); //char *sendbuffer = (char *) calloc(300, sizeof(char)); while (1) { ssize_t count = read(fd, dumpbuffer, 100); if (count < 0) return 1; dump_packet(fd, count, dumpbuffer); send_packet(fd); } return 0; } Wireshark shows the packet are exchanged as below. It's working! 1 0.000000000 203.0.113.2 203.0.113.1 ICMP 86 Echo (ping) request id=0x0019, seq=7/1792, ttl=64 (reply in 2) 2 0.000082333 203.0.113.1 203.0.113.2 ICMP 84 Echo (ping) reply id=0x0019, seq=7/1792, ttl=64 (request in 1)

Below is the database file which Nmap uses as a reference to packet info specific to OS. It is at /usr/share/nmap/nmap-os-db in the case of Ubuntu 20.04.4 LTS. # Linux 2.6.30-ARCH #1 SMP PREEMPT Wed Sep 9 12:37:32 UTC 2009 i686 AMD Athlon(tm) XP 2000+ AuthenticAMD GNU/Linux Fingerprint Linux 2.6.30 Class Linux | Linux | 2.6.X | general purpose CPE cpe:/o:linux:linux_kernel:2.6.30 SEQ(SP=C1-CB%GCD=1-6%ISR=C5-CF%TI=Z%II=I%TS=U) OPS(O1=M5B4NNSNW6%O2=M5B4NNSNW6%O3=M5B4NW6%O4=M5B4NNSNW6%O5=M5B4NNSNW6%O6=M5B4NNS) WIN(W1=16D0%W2=16D0%W3=16D0%W4=16D0%W5=16D0%W6=16D0) ECN(R=Y%DF=Y%T=3B-45%TG=40%W=16D0%O=M5B4NNSNW6%CC=N%Q=) T1(R=Y%DF=Y%T=3B-45%TG=40%S=O%A=S+%F=AS%RD=0%Q=) T2(R=N) T3(R=Y%DF=Y%T=3B-45%TG=40%W=16D0%S=O%A=S+%F=AS%O=M5B4NNSNW6%RD=0%Q=) T4(R=N) T5(R=Y%DF=Y%T=3B-45%TG=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=) T6(R=N) T7(R=Y%DF=Y%T=3B-45%TG=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=) U1(DF=N%T=3B-45%TG=40%IPL=164%UN=0%RIPL=G%RID=G%RIPCK=G%RUCK=G%RUD=G) IE(DFI=N%T=3B-45%TG=40%CD=S) The Nmap source code can be found here.

I'm curious how Nmap OS detection works. Project like below is something that I am interested! https://nmap.org/misc/defeat-nmap-osdetect.html

I added the below code to the previous post to receive ICMP packets. char *buffer = (char *) calloc(150, sizeof(char)); ssize_t count = read(fd, buffer, 100); Below is how read() can be used. The read() function shall attempt to read nbyte bytes from the file associated with the open file descriptor, fildes, into the buffer pointed to by buf. In the absence of errors, or if error detection is not performed, the read() function shall return zero and have no other results. reference Below is the received packet in hex. 00 00 08 00 45 00 00 54 89 4b 40 00 40 01 39 59 cb 00 71 01 cb 00 71 02 08 00 2a c7 00 19 00 07 c8 b6 8c 63 00 00 00 00 af 2b 0a 00 00 00 00 00 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37 The above shows that the source address is "cb 00 71 01->203.0.113.1" and the destination address is "cb 00 71 02->203.0.113.290". I'll try to send packets next time! I'm curious simply switching the source and destination address will be enough to send back the packet?

I created a TUN interface with the below c program. int main(int argc, char** argv) { if (argc != 2) return 1; const char* device_name = argv[1]; if (strlen(device_name) + 1 > IFNAMSIZ) { return 1; } int fd = open("/dev/net/tun", O_RDWR); if (fd == -1) { return 1; } struct ifreq ifr; memset(&ifr, 0, sizeof(ifr)); ifr.ifr_flags = IFF_TUN; strncpy(ifr.ifr_name, device_name, IFNAMSIZ); int res = ioctl(fd, TUNSETIFF, &ifr); if (res == -1) { return 1; } printf("the created device is only available during this program\n"); while (1) { } return 0; } The important part in the above code is below. You can provide the name of the interface to "ifr.ifr_name" and spcify whether you want the interface to be TUN or TAP with "ifr.ifr_flags". int fd = open("/dev/net/tun", O_RDWR); int res = ioctl(fd, TUNSETIFF, &ifr); There is another way of creating TUN device using ip command which is shown below. $ sudo ip tuntap add dev tun0 mode tun My next attempt is to receive and read packets using read() and send(). I also want to see how packets are being exchanged using Wireshark.

Maybe TUN/TAP is a good place to start understanding how low-level networking works?

You can check the file descriptor and associated device files with the below command. $ lsof cat 307 ryo 1w REG 8, 32 0 106248 /home/ryo/ctf/kernel/file1.txt Above shows that device files have major and minor numbers to identify the associated device drivers. You can see that 8, 32 are the major and minor number in the above case. You can check which device number has 8, 32 by the below command. /dev$ ls -la brw------- 1 root root 8, 32 Nov 23 11:51 sdc Maybe I should start looking into device drivers used for networking?

I used Wireshark to observe how packets are exchanged between client and server. Packets are sent by client form some random port. Packets are received by the server with the specified port by the running program. Client socket program written in python import socket # AF_INET refers to ipv4 # SOCK_STREAM refers to TCP protocol clientSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # 3 way handshake(SYN) as socket.SOCK_STREAM is the selected type # clientSocket.connect(('127.0.0.1', 12345)) clientSocket.connect(('192.168.50.130', 1234)) dataFromServer = clientSocket.recv(1024) print(dataFromServer.decode()) Server socket program written in python import socket s = socket.socket() port = 12345 s.bind(('', port)) s.listen(5) while True: # 3 way handshake(ACK) as socket.SOCK_STREAM is the selected type clientSocket, addr = s.accept() print(addr) clientSocket.send('Thank you for connecting'.encode()) clientSocket.close() break Packets form Wireshark 1 0.000000000 127.0.0.1 127.0.0.1 TCP 74 44070 → 1234 [SYN] Seq=0 Win=65495 Len=0 MSS=65495 SACK_PERM=1 TSval=4210716831 TSecr=0 WS=128 2 0.000113299 127.0.0.1 127.0.0.1 TCP 74 1234 → 44070 [SYN, ACK] Seq=0 Ack=1 Win=65483 Len=0 MSS=65495 SACK_PERM=1 TSval=4210716831 TSecr=4210716831 WS=128

Some stuff I learned about socket programming ・client socket socket.socket, socket.connect ・server socket socket.connect, socket.bind, socket.listen, socket.accept Client socket sends SYN with socket.connect and server socket sends ACK with socket.accept. Server socket create client-like(temporary) socket for every incoming client socket.

Here are the books that I'm currently interested in! I always forget why I bought the books and ends up piling them up... So here I decided keep short notes that reminds me the intention and what interested me when I ordered them. They are queued and scheduled in to be read, not in fifo order, and also could be preempted. But still, I care about throughput as I'm not good at context switching haha. This is also to remind myself that there are still a lot of interesting stuff in this world, things make me want to dream up. One can ‘go too far’ and except in directions in which we can go too far there is no interest in going at all - T.S. Elliot If you have any books that you recommend, let me know! - 中立とは何か as of some time during April The book was preempted by this book haha. I will come back once I finish reading the book. - 大衆の反逆 as of sometime during April, IIRC I forgot why I bought the book, it was being piled up next to my Raspberry pi haha. And I started reading the book preempting this book. I wanted read something other than 方法論. The book is still in a state of TASK_RUNNING and sure to be back later on :) - シュルレアリスムとは何か as of 2025/05/20 My friend told me about this painter, Edward Hopper. So I googled it and bumped into this book. Not sure if surrealism has anything to do with him, but the impression I get from those painting made me curious where they come from. - オリエンタリズム 上 as of 2025/05/20 This book was also recommended by my friend. Must be interesting to look at Arabian Night from western perspective. - 社会学的方法の規準 as of 2025/05/30 I want to read this book after finishing this book. - マックス・ヴェーバー研究 as of 2025/06/04 How the discussion on one value has changed over time must be interesting, being aware of the very value that we hold from relative perspective, by placing ourselves in a reletive position in the course of history. Also, the shift of value must be reflecting how the society has changed over time, and that also interests me. 自分の観点を、他の対立する立場とのコンステレーション（布置連関）に位置づけて、可能なかぎり明晰に自覚化しようとする意識も希薄になりつつある。第一章で価値自由の暫定的な説明をしたときに、ウェーバーはいくぶん古い新カント派の価値哲学のヴォキャブラリーを引き継いでいると述べた。彼が使う価値という用語が古いことは否定できない。しかし、これらを古いと思うとき、私たちは一体、何を見失いつつあるのか。少なくともこの点を自らに問いかける必要はあるだろう。思想史の仕事の一つは、歴史的コンステレーションに今の時代を位置づけることである。価値というタームの意味がわかりにくくなっているとすれば、それが熱心に論じられていた時代から、現在を照らし直す必要がある。今この時代に安藤を読むということには、そうした意味がある。 - 中立とは何か - ラテンアメリカ文学入門 - ボルヘス、ガルシア・マルケスから新世代の旗手まで as of 2025/06/09 I'm interested in how surrealism lead to Latin American literature's Magical realism. The book sounds just right to read after this book. It's also for me to keep studying Spanish haha. - アメリカ文学のレッスン as of 2025/06/11 I know there are already number of books queued, maybe after this book. I just like those books which discusses what's behind the scene, and the scene sounded quite interesting by itself that I couldn't hold myself from hitting that "Buy Now" on Amazon😅. - Society of Singularities as of 2025/06/12 The book was introduced in this book, and this website seems to describe more about it. But I couldn't find the book in Japanse... Maybe its good to read books in English once in a while haha. There must be something discussed in the book that I can reflect on myself, reminding me the very reason why I want to learn. 個別性が重視される時代...批判的な対話では矛盾とみられる諸要素も"いろいろなオピニオンがある"ということで受け入れられていく...学問という仕事(ベルーフ)がそれを学ぶ者に提供できるものは、結局は"明晰さ"であると彼がいうとき、ある特定の価値に矛盾すること無く、一貫してコミットすることが想定されている - 社会学的想像力 as of 2025/6/17 I got baited by Amazon's below introduction, as always😅. なぜ社会学を学ぶのか。抽象的な理論や微細な調査に明け暮れる現状を批判し、個人と社会を架橋する学という原点から問い直す I like those moment realizing that I can associate and fit myself in the picture of social science, philosophy, history, or whatever that type of studies. It's like discovering yourself in somewhere totally new. Its the reason for me to want to travel to those places where reminds of such picture. - Invisible Man as of 2025/06/19 I was interested in how a boy as described figures things out in a society like below. Its also something I see similar in the discussion of Orientalism. 何も見ていない白人の視線によって黒人のアイデンティティが規定されるかぎり、黒人が真の意味で名を持つこともありえない。というメッセージは（不幸なことに）現在でも十分切実だろう - アメリカ文学のレッスン - 歴史とは何か as of 2025/6/21 I was interested in what he, someone who stated as below which I think gets to the very point, has to say about history, . 過去は現在の光に照らされて初めて知覚できるようになる。現在は過去の光に照らされて初めて十分理解できるようになる - E.H. Carr --- Note this post was actually made on 5/20/2025. I just forgot how to order it properly without modifying the date... All the stuff I learned on Javascript to make this blog has gone into oblivion🤣.

My 8 months video.

THIS VIDEO IS FROM YOUTUBE.

THIS VIDEO IS FROM INSTAGRAM.

THIS VIDEO IS FROM FACEBOOK.