dsa_8021q_rcv(9)

💅 dsa_8021q_rcv(9) — the kernel API manual, but make it make sense

Okay bestie, welcome to the dsa_8021q_rcv page from the Kernel API Manual ✨ — this is the girl whose whole job is decoding where a packet came from. No cap, she's a little legend.

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🎀 NAME 🎀

dsa_8021q_rcv — Decode source information from tag_8021q header 🦋

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✨ SYNOPSIS ✨

void dsa_8021q_rcv (struct sk_buff *skb , int *source_port , int *switch_id , int *vbid , int *vid );

Like, that's the whole vibe check right there 💫

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🌸 ARGUMENTS 🌸

• skb — the RX socket buffer, aka the packet showing up to the function's door 🚪
• source_port — pointer to storage for precise source port information. Okay so here's the tea: if this is already known from outside tag_8021q, the pre-initialized value is preserved. If it's not known, pass -1. Simple as that 💅
• switch_id — similar to source_port. Same rules, same energy 🫶
• vbid — pointer to storage for an imprecise bridge ID. This one's got rules, bestie: it must be pre-initialized with -1 ⚠️. And if a positive value comes back? Then source_port and switch_id are invalid. Periodt.
• vid — pointer to storage for the original VID, for the case where tag_8021q decoding failed 😭 (it happens to the best of us)

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💖 DESCRIPTION 💖

So here's what she actually does 🔥:

If the packet has a tag_8021q header, she decodes it and sets source_port, switch_id and vbid, then strips the header off. Iconic behaviour, honestly.

Otherwise — no header, no problem — she sets vid and keeps the header in the hwaccel area of the packet 🌈. Not me being precise about where the header lives, but like, that's literally where it lives.

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👑 SEE ALSO 👑

Kernel file ./net/dsa/tag_8021q.c — go read it, iykyk 📖✨

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Fr fr though: that vbid needs to arrive as -1 or the whole thing gets weird. Don't say I didn't warn you 🙈

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And that's a wrap, bestie 🎀 this chaotic little page lives in ./net/dsa, dated October 2026, and it's giving kernel-doc excellence ⭐ slay 💜