nf_hook(9)

📦 version 7.3.1, in nixpkgs unstable

Okay bestie, welcome to the nf_hook(9) page from the Kernel API Manual 🌸. This is the one about calling a netfilter hook, and the original is lowkey mysterious about the arguments. We are keeping every crumb exactly as it is, no cap ✨.

🌟 NAME 🌟

nf_hook — call a netfilter hook 🦋

✨ SYNOPSIS ✨

int nf_hook (u_int8_t pf , unsigned int hook , struct net *net , struct sock *sk , struct sk_buff *skb , struct net_device *indev , struct net_device *outdev , int (*okfn)(struct net *, struct sock *, struct sk_buff *) );

🎀 ARGUMENTS 🎀

Okay so the original manpage is giving absolutely zero lore for these, and I am not about to invent any. Every single one says -- undescribed --, periodt 💅:

  • pf — -- undescribed --
  • hook — -- undescribed --
  • net — -- undescribed --
  • sk — -- undescribed --
  • skb — -- undescribed --
  • indev — -- undescribed --
  • outdev — -- undescribed --
  • okfn — -- undescribed --

🔥 DESCRIPTION 🔥

Returns 1 if the hook has allowed the packet to pass ✅. The function okfn must be invoked by the caller in this case — like, the caller has to do it, no skipping 👑.

Any other return value indicates the packet has been consumed by the hook 💀. That is the whole description, bestie, and we are keeping it 100.

🌈 SEE ALSO 🌈

  • Kernel file ./include/linux/netfilter.h 📁

xoxo, your kernel bestie 💖 — source/version: ./include/linux · date: October 2026 · page: nf_hook(9) 🫶

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