UNION NFT_PIPAPO_MAP_BUCKET(9)

💅 union nft_pipapo_map_bucket(9) — the kernel API manual, but make it make sense

okay bestie so this is a page straight out of the Kernel API Manual (the union nft_pipapo_map_bucket(9) one, yes the whole name, i know), and it's lowkey one of those tiny little structures that's doing a LOT of heavy lifting behind the scenes in nftables pipapo set lookups. she's a union, she's a bucket, she's in the mapping table, and she ate. let's get into it 🫶

---

✨ NAME ✨

union nft_pipapo_map_bucket — literally just "Bucket of mapping table". that's her whole job description and she's iconic for it 💅

---

🌸 SYNOPSIS 🌸

so the shape of her is this, exactly this, no notes:

union nft_pipapo_map_bucket {
    struct {
  #if BITS_PER_LONG == 64;
      static_assert(NFT_PIPAPO_MAP_TOBITS <= 32);
      u32 to;
      static_assert(NFT_PIPAPO_MAP_NBITS <= 32);
      u32 n;
  #else;
      unsigned long to:NFT_PIPAPO_MAP_TOBITS;
      unsigned long  n:NFT_PIPAPO_MAP_NBITS;
  #endif;
    };
    struct nft_pipapo_elem *e;
 };

like, notice the #if BITS_PER_LONG == 64 branch? on a 64-bit machine she keeps it simple with plain u32 fields and static_asserts to prove they fit. on anything else she switches to bitfields. main character energy in BOTH configurations, fr fr ✨

---

🎀 Members 🎀

time for the cast list, and yes there's some doubling up in here, that's just how the page is written, don't come for me 😭

• {unnamed_struct} — anonymous. literally no name. mysterious. unknown. she simply exists 🕵️
• to — First rule number (in next field) this rule maps to
• n — Number of rules (in next field) this rule maps to
• to — First rule number (in next field) this rule maps to (yes, again — the page lists it twice, so i'm listing it twice 💀)
• n — Number of rules (in next field) this rule maps to (and again 🫠)
• e — If there's no next field, pointer to element this rule maps to

so the vibe is: if there IS a next field, to and n are your besties and they tell you where to go and how many rules live there. if there's NO next field, e steps up and points straight at the element. one or the other, she's a union after all 💖

---

👑 SEE ALSO 👑

go read these next, bestie, they're all in the same friend group:

• Kernel file ./net/netfilter/nft_set_pipapo.h struct nft_pipapo_field(9)
• struct nft_pipapo_scratch(9)
• struct nft_pipapo_match(9)
• struct nft_pipapo(9)
• struct nft_pipapo_elem(9)
• pipapo_and_field_buckets_4bit(9)
• pipapo_and_field_buckets_8bit(9)
• pipapo_estimate_size(9)
• pipapo_resmap_init(9)

---

and that's the whole page, no cap 🌈

signing off from ./net/netfilter — the source, the whole source, and nothing but the source — dated October 2026, with union nft_pipapo_map_bucket(9) living in the footer where she belongs. slay 💜🎀✨