tcp_retransmit_timer(9)

📦 version 7.3.1, in nixpkgs unstable

💅 tcp_retransmit_timer(9) — kernel API manual, but make it make sense

okay so bestie, welcome to tcp_retransmit_timer(9) — that's section 9 of the Kernel API Manual, aka the deep-internals zone where only the brave (and the network stack girlies) hang out. pull up a chair, we're talking about the TCP retransmit timeout handler and honestly? it's lowkey iconic. ✨

🌸 NAME 🌸

tcp_retransmit_timer — literally the TCP retransmit timeout handler. that's her. that's the whole vibe. 👑

🎀 SYNOPSIS 🎀

void tcp_retransmit_timer (struct sock *sk );

no cap, that's the whole signature. copy it exactly, don't get cute with it.

🦋 ARGUMENTS 🦋

  • sk — a pointer to the current socket. yeah, just the one. she's the main character of this function, everything revolves around her. 💖

🔥 DESCRIPTION 🔥

so here's the tea: this function gets called when the kernel timer for a TCP packet of this socket expires. the clock ran out, the vibe check failed, and now somebody's gotta deal with it — and that somebody is tcp_retransmit_timer.

what does she actually do while she's there? three things, periodt:

  • she handles retransmission (the packet's getting another shot, fr fr)
  • she handles timer adjustment (the timing gets reworked)
  • she handles other necessary measures (the rest of the grown-up business that keeps the whole thing from falling apart) 🫶

it's giving main character energy, honestly — one expired timer and she's out here keeping everything together. 😭

⭐ RETURN ⭐

nothing. literally nothing. she returns void.

no value, no exit code, no little note in your inbox. she does the work and dips. 💀

🌈 SEE ALSO 🌈

the kernel file ./net/ipv4/tcp_timer.c — that's where the magic lives, go read her:

iykyk, these are the whole friend group. go say hi. 🧚

fair warning bestie: this is kernel-level code — no hand-holding, no guardrails, no "are you sure?" popup. know what you're doing before you go poking at timers. 💜

okay that's the page!! 🍓 this little masterpiece lives in ./net/ipv4 and it's dated October 2026 — so yeah, timestamped and everything, very official, very slay. mwah, go forth and retransmit responsibly. 💅✨🎀

📦 where this page comes from