VAR XT_RECSEQ(9)

💖 var xt_recseq(9) 💖

okay so welcome to the Kernel API Manual bestie — today’s main character is var xt_recseq(9), and it’s giving netfilter recursion realness ✨

🌸 NAME 🌸

xt_recseq — recursive seqcount for netfilter use 🌀

✨ SYNOPSIS ✨

DECLARE_PER_CPU(seqcount_t, xt_recseq);

🦋 Description 🦋

Packet processing changes the seqcount only if no recursion happened. no cap. So get_counters can use read_seqcount_begin/read_seqcount_retry, because we use the normal seqcount convention: Low order bit set to 1 if a writer is active. periodt 💅

bestie, that low-order-bit thing is the vibe check for whether a writer is active — keep it exactly as stated 👑

🎀 SEE ALSO 🎀

• Kernel file ./include/linux/netfilter/x_tables.h 📁
• struct xt_action_param(9)
• struct xt_mtchk_param(9)
• struct xt_mtdtor_param(9)
• struct xt_tgchk_param(9)
• xt_write_recseq_begin(9)
• xt_write_recseq_end(9)

okay that’s the whole page — huge cute sign-off to the source/version + date stamp: source ./include/linux/netfilter, date October 2026, mwah 💋🫶