iptunnel_pmtud_check_icmp(9)

hey bestie!! welcome to iptunnel_pmtud_check_icmp(9) from the Kernel API Manual 💖 this is the page for the function that triggers an ICMP reply if needed and allowed — yes, it’s giving very “do I need to send a little network message back?” energy ✨

🌸 NAME 🌸

iptunnel_pmtud_check_icmp — Trigger ICMP reply if needed and allowed 💅

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✨ SYNOPSIS ✨

int iptunnel_pmtud_check_icmp (struct sk_buff *skb , int mtu );

okay so that’s the whole signature, bestie — copy it exactly, no cap 😌

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🎀 ARGUMENTS 🎀

• skb — the buffer being sent by encapsulation, and it expects L2 headers 🫶
• mtu — the network MTU for the path 🌈

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💜 RETURN 💜

• 0 for no ICMP reply 🙈
• length if built 📏
• negative value on error 😭

bestie the return values are literally the whole vibe check here: 0 means no reply, length means it built one, and negative means something went wrong 💀

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🦋 SEE ALSO 🦋

• Kernel file ./net/ipv4/ip_tunnel_core.c — go look at it, iykyk 👀
• iptunnel_pmtud_build_icmp(9) ✨
• iptunnel_pmtud_build_icmpv6(9) 🧚
• iptunnel_pmtud_check_icmpv6(9) 💖
• skb_tunnel_check_pmtu(9) 🔥

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and that’s the page, bestie!! 🎀 source/version line says ./net/ipv4, dated October 2026, and the whole thing is iptunnel_pmtud_check_icmp(9) — periodt 💅✨