In this live stream, we look at the source code for Linux's implementation of the Berkeley socket API. We also look at "socks" (no "et"), which seem to contain the lower-level implementation details for "sockets". In a now time-honored tradition, I confuse the right and left shift operators. And @Raxneff Nextnerf and others help me out with some of the thornier details in the code. Along the way, we take a detour to learn a bit about how to optimize C structs for cache locality. Useful links: - Socket.h: https://github.com/torvalds/linux/blob/master/include/linux/socket.h - Socket.c: https://github.com/torvalds/linux/blob/master/net/socket.c - Sock.h: https://github.com/torvalds/linux/blob/master/include/net/sock.h - Sock.c: https://github.com/torvalds/linux/blob/master/net/core/sock.c Related videos: - Linux kernel: https://www.youtube.com/watch?v=C43VxGZ_ugU - TCP: https://www.youtube.com/watch?v=8PVufdYi2zs Sorry about the harsh sound on this video, I accidentally plugged my microphone into the wrong channel 🤦‍♂️. Thanks for watching :) https://www.youtube.com/channel/UCSjPewKdcullIrS7xSbzvrw put together the following timeline: 00:00:15 What this live show is about 00:03:28 socket.c 00:05:06 includes in socket.c 00:07:30 opening files 00:13:44 socket address families in socket.h 00:15:35 protocol families in socket.h 00:16:25 flags for send/recv in socket.h 00:17:13 setsockoptions level in socket.h 00:11:54 basic functions in socket.h 00:18:33 sockaddr in socket.h 00:19:32 sockaddr_storage in socket.h 00:20:02 msghdr in socket.h 00:24:06 Linux socket API 00:26:35 for_each_cmsghdr in socket.h (PLEASE, do not touch) 00:29:04 msg_data_left in socket.h 00:32:04 control message types in socket.h 00:32:49 recvmsg in socket.h 00:35:36 sendmsg lookup man page 00:38:49 What I think sock.h is about 00:39:23 includes in sock.h 00:40:34 SOCK_DEBUG in sock.h 00:41:04 socket_lock_t sock.h 00:42:59 sock_common struct in sock.h 00:49:22 SO_REUSEADDR lookup 00:43:10 for what the unions are used 00:53:03 tcp timewait lookup 00:55:51 sock.h (cont.) 00:56:07 sock structure in sock.h 00:58:45 we are in lower level land 01:02:11 sound issues 01:04:04 How ordering of elements in structs can help performance 01:09:18 back in sock.h 01:10:13 optimisation in sock.h and Google QUIC 01:15:04 CPU caches 01:22:09 further stuff in sock.h 01:23:11 sk_page_frag ... in sock.h 01:23:50 sk_pacing_shift_update and right-shift for ms 01:31:13 socket.c 01:32:30 file_operations ... in socket.c 01:34:22 spinlock in socket.c 01:34:40 support routines and audit_sockaddr in socket.c 01:35:17 sockfs_dname in socket.c 01:36:38 sock_alloc_file in socket.c 01:38:48 sock_sendmsg in socket.c 01:39:17 Linux Security Modules 01:39:53 socket.c (cont.) 01:40:35 __sock_recv_timestamp and more in socket.c 01:43:01 sock.c 01:43:03 includes in sock.c 01:45:20 sk_clear_memalloc in sock.c 01:46:26 timeout, netstamp, ... -stuff in sock.c 01:47:53 sk_setsockopt in sock.c 01:52:21 static_branch_unlikely lookup 01:56:45 outro and what comes next