mtype_add_cidr(9)

💅 mtype_add_cidr — like, the whole manual page, bestie ✨

okay so you're looking at mtype_add_cidr(9) — yes, section 9, that's the Kernel API Manual, we're doing kernel-level stuff today and honestly? iconic of you. 🎀 This little function is the one that slips a CIDR entry into the hash table's bookkeeping, and I'm gonna walk you through every single bit of it, no cap. 🦋

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🌸 NAME 🌸

mtype_add_cidr — adds a CIDR entry to the hash table bookkeeping, literally that's the whole job 💖

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✨ SYNOPSIS ✨

int mtype_add_cidr (struct ip_set *set , struct htype *h , u8 cidr , u8
n );

that's it. that's the signature. copy it exactly, don't be cute with it 🙈

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🫶 ARGUMENTS 🫶

• set — pointer to the ip_set. like, the set. the actual one. keep your eyes on it 👀
• h — pointer to the htype. the type-hash buddy that comes along for the ride.
• cidr — the CIDR prefix length 🧚 that's the number that goes in.
• n — the index of the net_prefix array to add cidr to. yes, which array slot. very specific. we love that for us ⭐

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🔥 DESCRIPTION 🔥

so here's the vibe check on how this actually goes down:

• if cidr is found, it performs an update 💫 (no drama, just refresh)
• otherwise? it does COW-style allocation and replacement via RCU. copy-on-write, bestie. allocate the new thing, swap it in under RCU, and everyone else keeps reading the old one peacefully. it's giving main character energy but for concurrency 🌈

⚠️ that COW + RCU part is the whole personality of this function — nothing gets mutating in place, so don't go assuming the old memory just vanishes on you 💀

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👑 RETURN 👑

• 0 — success, slay, we ate 🎉
• negative error code — failure 😭 (negative, so like, not zero, okay? check it. always check it.)

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🎀 SEE ALSO 🎀

• the kernel file ./net/netfilter/ipset/ip_set_hash_gen.h — that's where it lives, go read it 💜
• struct net_prefix(9)
• struct net_prefixes(9)
• mtype_del_cidr(9) — the one that takes it back out, the breakup arc 🦋

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and that's the whole page, bestie 🍓 this masterpiece is brought to you by the source at ./net/netfilter/ipset, dated October 2026 — periodt, go forth and add those CIDRs 💅✨🔥