KNET_HAND...CK_NOTIFY(3)

📦
version 1.35 · 7 versions
, in fedora 43, fedora 44

💖 KNET_HAND...CK_NOTIFY(3) 💖

okay bestie, welcome to the Kronosnet Programmer's Manual — this is the page for knet_handle_enable_sock_notify, and it's lowkey one of the most important ones bc it's literally how you find out your sockets are having a moment 🫶

✨ NAME ✨

knet_handle_enable_sock_notify — register a callback so you can get notified about socket events, no cap 📣

🌸 SYNOPSIS 🌸

#include <libknet.h>

int knet_handle_enable_sock_notify(
    knet_handle_t  knet_h,
    void          *sock_notify_fn_private_data,
    void(*)(void *private_data, int datafd, int8_t channel, uint8_t tx_rx, int error, int errorno)  sock_notify_fn
);

🦋 DESCRIPTION 🦋

So the function is knet_handle_enable_sock_notify, and here's the whole vibe:

  • knet_h — pointer to knet_handle_t 💅 that's your handle, your main character, the whole thing.
  • sock_notify_fn_private_data — a void pointer to data you can use to identify the callback. like a little name tag for your callback so you know who's who at the party 🎀
  • sock_notify_fn — a callback function that gets invoked every single time a socket in the datafd pool reports an error (-1) or an end of read (0) (see socket.7).
⚠️ This function MUST NEVER block or add substantial delays. Not even a little. It's giving "quick check-in", not "let me think about it". 😭

The callback is invoked in an internal unlocked area — that's on purpose, bestie — so that calls to knet_handle_add_datafd/knet_handle_remove_datafd are allowed to swap/replace the bad fd. ✨

And here's the detail that trips people up: if both err and errno are 0, that means the socket has received a 0 byte packet (EOF?). 👀

The callback function must either remove the fd from knet (by calling knet_handle_remove_fd()) or dup a new fd in its place. Failure to do this can cause problems. like, actual problems. don't skip this step fr fr 💀

⭐ RETURN VALUE ⭐

knet_handle_enable_sock_notify returns 0 on success, -1 on error, and errno is set. periodt. 👑

💜 SEE ALSO 💜

the whole friend group showed up, and we are obsessed:

Copyright (C) 2010-2026 Red Hat, Inc. All rights reserved.

and that's the page bestie!! 💖 this lil manual page is from kronosnet, dated 2026-07-20 — slay, go forth and never block in your callback 🧚✨

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