sk_attach_filter(9)

💖 sk_attach_filter(9) 💖

okay so bestie, welcome to the Kernel API Manual — this one's a lil function called sk_attach_filter, and honestly? it's giving "let the user hand you a filter and hope for the best" energy. let's get into it 🎀

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✨ NAME ✨

sk_attach_filter — attach a socket filter 🦋

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🌸 SYNOPSIS 🌸

int sk_attach_filter (struct sock_fprog *fprog , struct sock *sk );

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💅 ARGUMENTS 💅

• fprog — the filter program, aka the actual code the user wants to run. this is the main character 😌
• sk — the socket to use. this is where the filter's gonna live 🔥

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⭐ DESCRIPTION ⭐

so here's the vibe: you're attaching the user's filter code to the socket. no cap, that's literally the whole job 💖

but before we commit to anything, we run some sanity checks on the filter — just to make sure it doesn't explode on us later 😭 like, we're being responsible besties here. nobody wants a filter that goes feral three hours in.

if something goes wrong, or if there just isn't enough memory for the filter, you get a negative errno code back. that's the "nope, didn't work" signal, and it's negative, so watch for it 👀

on success, the return is zero. slay. 🎀

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🫶 SEE ALSO 🫶

• Kernel file ./net/core/filter.c
• sk_filter_trim_cap(9)
• bpf_convert_filter(9)
• bpf_check_classic(9)
• sk_filter_release_rcu(9)
• sk_filter_release(9)
• bpf_prog_create(9)
• bpf_prog_create_from_user(9)
• xdp redirect(9)
• bpf_skb_meta_pointer(9)
• bpf_dynptr_from_skb_meta(9)
• bpf_xdp_pull_data(9)
• bpf_icmp_send(9)

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okay that's the whole page, ily, go attach some filters responsibly 🧚💜

signed, sealed, delivered from ./net/core — October 2026 edition ⭐