get_ipv6_ext_hdrs(9)

🌸 get_ipv6_ext_hdrs(9) — kernel API manual, but make it make sense 🌸

okay bestie, so this one is a function from the kernel API manual (get_ipv6_ext_hdrs(9), section 9, the kernel-y one) and it's lowkey doing detective work on your packets. let's get into it 💅

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✨ NAME ✨

get_ipv6_ext_hdrs — parses a packet and sets the IPv6 extension header flags. that's it, that's the whole job. she reads, she flags, she slays 🔥

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🦋 SYNOPSIS 🦋

void get_ipv6_ext_hdrs (struct sk_buff *skb , struct ipv6hdr *nh , u16
*ext_hdrs );

yes it returns void, no she does not give you a return value, she gives you flags instead. main character energy honestly 👑

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🎀 ARGUMENTS 🎀

• skb — the buffer where the extension header data starts in the packet 🫶
• nh — the ipv6 header
• ext_hdrs — this is where the flags get stored, so like, that's the output spot bestie 💖

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💜 DESCRIPTION 💜

so OFPIEH12_UNREP gets set if you unexpectedly run into more than one of a given IPv6 extension header. like, rude?? but there's a lil exception: two destination options headers may be expected, and those would not cause this bit to be set. so don't come for that one 🙈

OFPIEH12_UNSEQ gets set if the IPv6 extension headers were not in the order that RFC 2460 prefers (key word: preferred, not required — she's not enforcing, she's just judging a little 💅).

and when more than one extension header shows up in the same packet, the recommendation is that they appear in this exact order:

1. IPv6 header
2. Hop-by-Hop Options header
3. Destination Options header
4. Routing header
5. Fragment header
6. Authentication header
7. Encapsulating Security Payload header
8. Destination Options header
9. upper-layer header

like the original spells it out as one long line, but bestie, a numbered list is right there — same headers, same order, no cap 🌈

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🧚 SEE ALSO 🧚

• Kernel file ./net/openvswitch/flow.c
• parse_vlan_tag(9)
• key_extract_l3l4(9)
• key_extract(9)

go read those too, iykyk 📚✨

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ngl this one's a vibe check for packets: repeat headers → flag, wrong order → flag. she's not mad, she's just setting bits 🍓

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and that's the page!! brought to you by ./net/openvswitch, dated October 2026, same as always — mwah, go touch some packets 💋👑💖