STRUCT SCM_TIMESTAMPING(9)

💅 struct scm_timestamping(9) — from the Kernel API Manual, bestie

okay so picture this: you're deep in the kernel docs, the manual is literally called Kernel API Manual, and you open up struct scm_timestamping(9). that's our girl. she's not complicated, she's just specific, and we're gonna get into it. 🎀

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✨ NAME ✨

struct scm_timestamping — timestamps exposed through cmsg. that's the whole vibe. timestamps, but delivered via cmsg, iykyk. ⭐

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🦋 SYNOPSIS 🦋

here's the actual shape of her, and yes, we're keeping every character, no cap:

struct scm_timestamping {
  #ifdef __KERNEL__;
    struct __kernel_old_timespec ts[3];
  #else;
    struct timespec ts[3];
  #endif;
 };

look at that conditional. she's showing one face to the kernel and another to user space. main character energy honestly. 👑

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🌸 Members 🌸

(this section is literally empty on the page — nothing listed, no members spelled out, just the heading sitting there. we love a minimalist moment. 💅)

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💖 Description 💖

so here's the tea. the timestamping interfaces SO_TIMESTAMPING and MSG_TSTAMP_* communicate network timestamps by passing this struct inside a cmsg with recvmsg. that's the whole delivery mechanism — struct goes in the cmsg, timestamp arrives, slay. 🚀

for the full details, the page points you at Documentation/networking/timestamping.rst. go read it, it's giving lore. 📖

now the tricky part, and you need to hear this one: user space sees a timespec definition that matches either __kernel_timespec or __kernel_old_timespec. in the kernel, we require two structure definitions to provide both. so yeah — two definitions, both required, because the kernel has to serve both flavors. not me having to juggle two entire struct definitions for one struct's sake 😭 literally the most try-hard part of the whole thing and I respect it.

🫶 reminder: none of this is optional flavor text — the #ifdef __KERNEL__ split in the synopsis is exactly why the description talks about two structure definitions. one struct, two faces, both required.

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🔥 SEE ALSO 🔥

• Kernel file ./include/uapi/linux/errqueue.h — go look, that's where she lives. ✨

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and that's the page!! 🌈 this iconic little entry ships out of ./include/uapi/linux, dated October 2026, and it's filed under struct scm_timestamping(9). mwah, go timestamp something, bestie 💜🍓🧚