llc_pdu_set_pf_bit(9)

💅 llc_pdu_set_pf_bit — from the Kernel API Manual ✨

okay so bestie, gather round, because this one is tiny but it's lowkey doing main character work inside your LLC header. The function is llc_pdu_set_pf_bit, and yes, it lives in section 9 of the Kernel API Manual, so you already know it's kernel-adjacent and mysterious 🎀

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✨ SYNOPSIS ✨

void llc_pdu_set_pf_bit (struct sk_buff *skb , u8 bit_value );

that's the whole vibe. void return, two args, in and out, no notes 💅

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🫶 ARGUMENTS 🫶

• skb — the frame you're gonna set the bit in. like, the actual packet. the main character of the operation 🌸
• bit_value — the poll/final bit value, and it's strictly 0 or 1. that's it. that's the whole range. no in-between, no "maybe", no 2 🙈

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🔥 DESCRIPTION 🔥

so what does it do? It sets the poll/final bit in the LLC header, and the exact spot it pokes depends on the type of PDU — the way that this function is type-aware is honestly iconic ✨

• in I or S pdus, the p/f bit is the right bit of the fourth byte in the header
• in U pdus, the p/f bit is the fifth bit of the third byte

that's the whole map, bestie. two different neighborhoods depending on which PDU you're rolling with, and this function knows which one to visit. no cap 🧚

⚠️ heads up: the byte and bit positions are different for I/S versus U PDUs, so don't go assuming one layout fits all — that's literally the reason this helper exists instead of you hand-poking bits like a menace 💀

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👑 SEE ALSO 👑

the whole extended friend group 🫶 — kernel file ./net/llc/llc_pdu.c, plus:

• llc_pdu_decode_pf_bit(9)
• llc_pdu_init_as_disc_cmd(9)
• llc_pdu_init_as_i_cmd(9)
• llc_pdu_init_as_rej_cmd(9)
• llc_pdu_init_as_rnr_cmd(9)
• llc_pdu_init_as_rr_cmd(9)
• llc_pdu_init_as_sabme_cmd(9)
• llc_pdu_init_as_dm_rsp(9)
• llc_pdu_init_as_frmr_rsp(9)
• llc_pdu_init_as_rr_rsp(9)
• llc_pdu_init_as_rej_rsp(9)
• llc_pdu_init_as_rnr_rsp(9)
• llc_pdu_init_as_ua_rsp(9)
• llc_pdu_decode_pdu_type(9)
• llc_pdu_get_pf_bit(9)

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and that's the page, bestie 💖 this whole thing ships out of ./net/llc, dated October 2026, and the manual name at the top is llc_pdu_set_pf_bit(9) — go set some bits, slay, and remember: 0 or 1, periodt 🌈⭐