skb_condense(9)

💅 skb_condense — a Kernel API Manual moment (section 9, bestie)

okay so real talk, this is from the Kernel API Manual, section 9, and the whole vibe is "clean up your skb's memory situation before it goes somewhere busy." Let's get into it 🫶

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✨ NAME ✨

skb_condense — try to get rid of fragments/frag_list if possible

Like, literally just vibes-based defragmentation. if it can, it will 💅

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🌸 SYNOPSIS 🌸

void skb_condense (struct sk_buff *skb );

🦋 ARGUMENTS 🦋

• skb — buffer. that's it. that's the whole argument. the buffer in question 💖

🔥 DESCRIPTION 🔥

So here's the tea: you can use this to save memory before skb is added to a busy queue. If the packet has bytes sitting in frags, and there's enough tail room in skb->head, it pulls all of them — so we can free the frags right now and adjust truesize. it's giving "tidying your room before guests arrive" energy, honestly 🧹✨

⭐ NOTES ⭐

Important caveats, no cap:

• We do not reallocate skb->head, thus it can not fail. iconic, honestly 👑
• Caller must re-evaluate skb->truesize if needed. don't forget, bestie — that's on you 🙈

🌈 SEE ALSO 🌈

Kernel file ./net/core/skbuff.c, plus the entire extended friend group of skb functions (yes, all of them, I'm not skipping anyone, that would be rude):

• 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_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_ext_alloc(9), __skb_ext_set(9), skb_ext_add(9), skb_attempt_defer_free(9), skb_splice_from_iter(9)

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okay that's the whole page, mwah 💋 this cutie lives over in ./net/core and the copy you're reading is dated October 2026 — so like, recent. slay. go condense some skbs, bestie 🎀🦋✨