skb_expand_head(9)

🌸 NAME 🌸

Okay bestie, welcome to skb_expand_head(9) from the Kernel API Manual — this is the page about reallocating the header of &sk_buff. Periodt.

• skb_expand_head — reallocate header of &sk_buff.

✨ SYNOPSIS ✨

struct sk_buff * skb_expand_head (struct sk_buff *skb , unsigned int
       headroom );

🎀 ARGUMENTS 🎀

• skb — the buffer you're reallocating, bestie.
• headroom — the needed headroom. That's the whole vibe.

🦋 DESCRIPTION 🦋

So unlike skb_realloc_headroom, this one does not allocate a new skb if it can avoid it — highkey efficient. It copies skb->sk to the new skb as needed, and if things fail, it frees the original skb. 💅

It expects increased headroom and generates a warning otherwise. Like, don't come at it with less headroom unless you want the warning vibe check. 😭

🌈 SEE ALSO 🌈

Kernel file ./net/core/skbuff.c — and the whole see-also friend group is giving linked-list energy:

• drop_reasons_register_subsys(9), drop_reasons_unregister_subsys(9), skb_panic(9), napi_skb_cache_get_bulk(9), __build_skb(9), build_skb_around(9), __napi_build_skb(9), napi_build_skb(9), __alloc_skb(9), __netdev_alloc_skb(9)
• napi_alloc_skb(9), skb_pp_cow_data(9), skb_pp_frag_ref(9), __kfree_skb(9), sk_skb_reason_drop(9), skb_tx_error(9), consume_skb(9), __consume_stateless_skb(9), napi_consume_skb(9), alloc_skb_for_msg(9)
• skb_morph(9), skb_copy_ubufs(9), skb_clone(9), skb_copy(9), __pskb_copy_fclone(9), pskb_expand_head(9), skb_copy_expand(9), __skb_pad(9), pskb_put(9), skb_put(9)
• skb_push(9), skb_pull(9), skb_pull_data(9), skb_trim(9), __pskb_pull_tail(9), skb_copy_bits(9), skb_store_bits(9), skb_zerocopy(9), skb_dequeue(9), skb_dequeue_tail(9)
• skb_queue_purge_reason(9), skb_rbtree_purge(9), skb_queue_head(9), skb_queue_tail(9), skb_unlink(9), skb_append(9), skb_split(9), skb_shift(9), skb_prepare_seq_read(9), skb_seq_read(9)
• skb_abort_seq_read(9), skb_copy_seq_read(9), skb_find_text(9), skb_pull_rcsum(9), skb_segment(9), skb_to_sgvec(9), skb_cow_data(9), skb_clone_sk(9), skb_partial_csum_set(9), skb_checksum_setup(9)
• skb_checksum_maybe_trim(9), skb_checksum_trimmed(9), skb_try_coalesce(9), skb_scrub_packet(9), skb_eth_pop(9), skb_eth_push(9), skb_mpls_push(9), skb_mpls_pop(9), skb_mpls_update_lse(9), skb_mpls_dec_ttl(9)
• alloc_skb_with_frags(9), skb_condense(9), __skb_ext_alloc(9), __skb_ext_set(9), skb_ext_add(9), skb_attempt_defer_free(9), skb_splice_from_iter(9)

🫶 and that's the tea: source/version ./net/core, date October 2026, manual skb_expand_head(9). Bye bestie! 💖