Month: October 2021

Hacker News 拿到 hackernews.com 了

在 Hacker News 上看到「Hackernews.com (hackernews.com)」這則消息，有人注意到 hackernews.com 被指到 news.ycombinator.com...

一開始有人猜測只是第三方指過來：

LeoPanthera 1 day ago

With a different registrar to ycombinator.com, this is likely not owned by Y Combinator, and therefore difficult to trust that it won't start being malicious in the future.

不過後來 dang (Hacker News 的管理員) 有出來證實這個網域名稱目前是在他們旗下了：

dang 1 day ago

It's owned by YC now. We got it earlier this year. That's why it redirects to HN!

以 Hacker News 的性質來說不是太重要，算是有機會拿掉就順便拿下來...

Framework 筆電也遇到缺料問題，換了音源晶片

Framework 的筆電最近在社群很紅，模組化設計讓維修變容易，而且也有許多規格上的客製化空間。在「Marketplace」這頁可以看到很多東西可以換，除了比較常見的無線網卡、SSD、記憶體以外，像是主機板、鍵盤甚至連 USB、HDMI 接口都是模組。

不過這邊要提到的是 audio chip 也在這波 supply chain 的供貨問題而中招了：「Solving for Silicon Shortages」，Hacker News 上的討論「Framework: Solving for Silicon Shortages (frame.work)」也可以看一下。

從文章裡看起來是 Realtek ALC295 的交期爆炸了：

Chips that would normally have 16-20 week lead times (meaning we’d place typically binding orders that far ahead of needing parts in our hands) went up to 52 weeks. In one case, we even got notified of a 68 week lead time on a chip!

We were able to get enough Realtek ALC295 audio CODECs to develop the Framework Laptop and get through the first few months of production, but nowhere near enough to fulfill ongoing demand from the US and Canada, let alone the additional countries we’d like to ship to.

所以決定換到 Tempo 92HD95B：

Luckily, we were able to find an alternative CODEC that lets us stay in production: the Tempo 92HD95B.

查了一下 datasheet，本來的 Realtek ALC295 是 QFN-48，而 Tempo 92HD95B 是 QFN-40，看起來得改不少東西... 應該是連 open market 上都翻不到而被迫換設計，跟我們家的情況也很像，看起來最近大家都哭到爆炸了 :o

Raspberry Pi 4 2GB 版本「暫時」漲價，另外 1GB 版本回歸

Raspberry Pi 宣佈 Raspberry Pi 4 的 2GB 版本將從 US$35 漲到 US$45，另外本來淘汰掉的 1GB 版本回歸，賣 US$35：「Supply chain, shortages, and our first-ever price increase」。

In February last year, we announced that we were discontinuing the 1GB variant of Raspberry Pi 4, and moving the 2GB product to our signature price of $35. We’re still glad we did this, as countless young people made use of this device as they studied from home during the pandemic.

Unfortunately, cost increases caused by the current shortage mean that this product is not currently economically viable at this reduced price point. We are therefore moving it back to $45 on a temporary basis.

To support the many industrial customers who have designed the 2GB variant of Raspberry Pi 4 into their products, we are reintroducing the 1GB variant at the $35 price point. This provides a degree of choice: less memory at the same price; or the same memory at a higher price.

然後共用 40nm 製程的 3B+ 會暫時先被降低優先權，產能會優先提供給 CM3、CM3+ 與 3B：

In allocating our limited stocks of 40nm silicon, we will prioritise Compute Module 3, Compute Module 3+, and Raspberry Pi 3B, and deprioritise Raspberry Pi 3B+.

整個供應鏈的情況被炸的亂七八糟...

FreeBSD 把 root 預設的 shell 改成 /bin/sh

在 Hacker News 首頁上看到 FreeBSD 把 root 的 shell 從 /bin/csh 換成 /bin/sh 了：「sh(1): make it the default shell for the root user」，Hacker News 上的討論也可以看一看：「FreeBSD switches the default root shell from csh to sh (freebsd.org)」。

依照說明是把 FreeBSD 的 /bin/sh 加上了不少東西，所以算是堪用了：

In the recent history sh(1) has gain the missing features for it to
become a usable interractive shell:
- command completion
- persistent history support
- improvements on the default bindings in emacs mode
- improvements in the vi mode (repect $EDITOR)
- print a newline when exiting via ^D
- default prompt and improvements on how PS1 can be configured
- and more.

This changes also simplifies making tiny freebsd images with only sh(1)
as a shell

以前也是用 csh 系列的 (像是 tcsh)，後來開始用 Linux 就往 Bash 與 Zsh 定居了...

用 iptables 擋特定國家的封包

這兩天發現 ubuntu-20.04.3-live-server-amd64.iso 這個 BitTorrent 的 ISO image 有大量來自 CN 的連線在狂抓，導致整個上傳頻寬都被吃滿：

沒想到第一次用 iptables 的 xt_geoip 居然是這個用途... 主要是參考「GeoIP Blocking Ubuntu 20.04LTS」這邊的方法，不過因為我的 rtorrent 是跑在 Docker 裡面的，有另外要注意的地方。

首先是安裝軟體，這邊要裝 xtables-addons-common 與 libtext-csv-xs-perl：

sudo apt install -y libtext-csv-xs-perl xtables-addons-common

再來是建立目錄，並且下載一包 GeoIP 的資料 (從 DBIP 下載) 並且轉成 xt_geoip 可以用的格式：

sudo mkdir /usr/share/xt_geoip
cd /usr/share/xt_geoip
sudo /usr/lib/xtables-addons/xt_geoip_dl
sudo /usr/bin/perl /usr/lib/xtables-addons/xt_geoip_build

然後就是加到 iptables 的條件裡面了，我加到兩個地方，一個是 INPUT chain，另外一個是 DOCKER-USER chain (參考「Docker and iptables」這邊的說明)，假設你是用 port 6991 的話就這樣加：

sudo iptables -I INPUT -p tcp -m geoip --source-country CN -m tcp --dport 6991 -j DROP
sudo iptables -I DOCKER-USER -p tcp -m geoip --source-country CN -m tcp --dport 6991 -j DROP

然後可以考慮每個禮拜更新一次資料庫。

另外在找資料的時候發現「Free updated GeoIP legacy databases」這邊有人放出 MaxMind 的版本，不過免費版的應該都差不多，這邊就用 xtables-addons-common 內預設的。

弄完以後就正常多了...

Memcached 與 Redis 的比較

在「Memcached vs Redis - More Different Than You Would Expect」這邊看到對 Memcached 與 Redis 的分析。

這兩套軟體都很常被拿來用作 cache 機制，所以一般來說比較時就是比兩邊都有的東西 (如果你要 pub-sub 之類的東西，在這兩套裡面只有 Redis 有)。

最前面還是先講了對使用者 (開發者) 的差異，很明顯的是 Redis 對各種不同的資聊結構都有支援，這點可以從 Redis 被官方被稱作 Data Structures Server 就可以知道 (在「An introduction to Redis data types and abstractions」這篇可以看到)，而 Memcached 只支援了 key-value 架構。

不過如果是以 cache 來說，的確 key-value 架構就還蠻好用的。

後面就開始比較硬的主題了，提到了 Memcached 與 Redis 內部是怎麼使用記憶體的。

Memcached 的部份先提了 page/slab/chunk 的架構以及產生的效能限制與浪費，接著有提到 2020 年 refactor 的部份 (太久沒有看 Memcached 的消息，去年沒跟到這個部份)，讓多 CPU 的支援度更好。

Redis 則是靠 jemalloc 來處理這個部份，另外加上 background thread 的機制降低 fragment。

然後是比較 cache expiration 的部份，可以看到兩者用的演算法在現實世界中都夠用 (尤其是當作 cache 來用)，這部份跟印象中的架構差不多，應該是沒有太大變化。

最後是比較 cluster 的部份，Memcached 是 share nothing，所以沒什麼好說的，主要是靠 client library 實做 consistent hash 之類的架構打散；而 Redis 的話看起來有實做新的機制出來 (也沒跟到)，之後有機會再看看可以做到什麼程度。

不過好像沒提到 proxy 之類的架構，基本上各大公司都有自己幹：

少了這塊對於 cluster 架構的完整性差蠻多的。

文章最後沒有下定論一定要用哪個比較好，兩者都有強項與弱項，還是得看情況來處理。不過我自己還是很喜歡用 Memcached 就是了...

用 AWK 寫的 Git

前幾天看到的東西，用 AWK 寫的 Git：「Aho: A Git implementation in AWK.」，Hacker News 上的討論「A Git Implementation in Awk (github.com/djanderson)」也可以翻一下。

Aho 這個名字取自 AWK 的作者之一 Alfred Aho (AWK 中的 A)，然後查資料才發現他剛拿到去年 2020 的 Turing Award...

作者提到了為什麼會用 AWK 寫 Git，看起來就是個爽字 XDDD：

I've had the irrational desire to write something substantial in AWK for a while. Figured I might as well learn some Git internals while I scratch this itch.

然後他有提到他沒打算把網路相關的功能實做進去：

I don't plan to add network functionality to this (even though you totally can), so no clone or push.

是個有趣的專案，寫爽的 XD

EULA 不能禁止使用者 decompile 修 bug

Hacker News Daily 上翻到的，歐洲法院認為 EULA 不能禁止使用者 decompile 修 bug：「EU court rules no EULA can forbid decompilation, if you want to fix a bug (europa.eu)」，官方的英文版文件在這邊可以翻到，不過原始判決是法文：

* Language of the case: French.

這是 Top System SA 與比利時政府打的訴訟，法院認為修 bug 而需要 decompile 這件事情是合法的，即使考慮到 Article 6 的規範：

In the light of the foregoing considerations, the answer to the first question referred is that Article 5(1) of Directive 91/250 must be interpreted as meaning that the lawful purchaser of a computer program is entitled to decompile all or part of that program in order to correct errors affecting its operation, including where the correction consists in disabling a function that is affecting the proper operation of the application of which that program forms a part.

In the light of the foregoing considerations, the answer to the second question referred is that Article 5(1) of Directive 91/250 must be interpreted as meaning that the lawful purchaser of a computer program who wishes to decompile that program in order to correct errors affecting the operation thereof is not required to satisfy the requirements laid down in Article 6 of that directive. However, that purchaser is entitled to carry out such a decompilation only to the extent necessary to effect that correction and in compliance, where appropriate, with the conditions laid down in the contract with the holder of the copyright in that program.

案子看起來應該還有得打？看起來好像不是最終判決...

REQUEST for a preliminary ruling under Article 267 TFEU from the Cour d’appel de Bruxelles (Court of Appeal, Brussels, Belgium), made by decision of 20 December 2019, received at the Court on 14 January 2020[.]

但不管怎樣，算是有些東西出來了... 然後 Hacker News 上面的討論就看到一些很歡樂的例子：

This becomes incredibly interesting in terms of e.g. Denuvo. This anti-piracy middleware has been shown to make games unplayable, and this EU law seems to support removing it.

哭啊怎麼提到該死的 Denuvo XDDD

在 Linux (Ubuntu) 上跑透過 QEMU 跑 Windows/Mac/Linux 的工具

Hacker News Daily 上看到的工具：「Quickly create and run optimised Windows, macOS and Linux desktop virtual machines.」，對應的討論在「Quickemu: Quickly create and run optimised Win-10,11/macOS/Linux on Linux (github.com/wimpysworld)」這邊可以看到，可以減少自己要設定一堆 QEMU 參數。

雖然專案是支援多系統，但其實 Microsoft Windows 與 Linux 的部份在其他虛擬軟體都很簡單 (像是用 VirtaulBox)，大家馬上會注意到的重點還是 macOS 的部份，如果有自己弄過就會知道這東西有夠難裝的，而且跨版本有不同的安裝方式...

目前 Quickemu 支援四個版本：

Supported macOS releases:

  • High Sierra
  • Mojave
  • Catalina (Recommended)
  • Big Sur

然後可以看到幾乎所有目前能支援的功能都有設定上去了，包括 VirtIO 與 USB 的部份。

然後一些經典的問題，像是 Big Sur 的音源問題還是沒解：

Full Duplex audio works on macOS High Sierra, Mojave and Catalina.

  • macOS Big Sur has no audio at all.

在 Hacker News 的討論串裡面有提到有很多地方沒有檢查，這會是風險：

While I appreciate the effort, and the code is very readable. I just want to give a friendly warning that these shell scripts just download random stuff from the internet and run this random stuff without checking any integrity/signature.

下面的討論另外看到個冷知識，關於蘋果故意走 HTTP 下載 recovery image 是因為 HTTPS 太複雜，在 UEFI firmware 裡面實做容易產生被攻擊的點，所以決定自己透過其他機制確認正確性：

Apple Internet recoveryOS images are served over plain http, on purpose. The macrecovery.py script used by Quickemu uses http¹, though the server supports https.

https://support.apple.com/guide/security/recoveryos-and-diagnostics-environments-sec2512a0c09/web

> When the internet recovery and diagnostic modes were added to Mac computers in 2011, it was decided that it would be better to use the simpler HTTP transport, and handle content authentication using the chunklist mechanism, rather than implement the more complicated HTTPS functionality in the UEFI firmware, and thus increase the firmwareʼs attack surface.

¹https://github.com/acidanthera/OpenCorePkg/blob/4a740c3f256e285c66ca3b65e42b60af6826d343/Utilities/macrecovery/macrecovery.py#L123

[edit] Added macrecovery.py info

另外為了避免直接在 shell script 裡面出現「神秘字串」，可以看到特別的寫法 XDDD

Took a little while to find the magic words in there: https://github.com/wimpysworld/quickemu/blob/af26f41440d63a069045660fad860c797011310a/quickemu#L351

可以想到一些用途，像是在機房裡面跑 CI 的 worker，但要注意這個搞法不符合蘋果的 EULA，現在不抓不代表以後也不會有事，請自己謹慎評估...

然後往 ARM-based 架構後應該門檻就更高了，現在還有 Intel-based 的環境可以用加減用...