ppp_proto_is_valid(9)

💅 ppp_proto_is_valid(9) — like, the whole manual page, bestie

okay so welcome to ppp_proto_is_valid(9), the kernel API manual page that literally just checks if a PPP protocol number is valid ✨ it's a tiny little function but she's doing her job and we respect her for it 🫶

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🎀 NAME 🎀

ppp_proto_is_valid — checks if PPP protocol is valid 👑

✨ SYNOPSIS ✨

bool ppp_proto_is_valid (u16 proto );

🌸 ARGUMENTS 🌸

• proto — the PPP protocol 💫 (that's it, that's the whole argument, she's lowkey simple like that)

🦋 DESCRIPTION 🦋

so the deal is this: this function assumes proto is not compressed 🙈 like, no compression going on here, that's not her problem, she's not checking for that.

A protocol is valid if the value is odd and the least significant bit of the most significant octet is 0 — and yes, that's real, that's literally the rule (see RFC 1661, section 2) 📖✨ iykyk.

so to recap, both conditions, no cap:

1. the value is odd
2. the least significant bit of the most significant octet is 0

both? valid. slay 💅

🌈 SEE ALSO 🌈

• Kernel file ./include/linux/ppp_defs.h — go read it, she's iconic
• ppp_skb_is_compressed_proto(9) — the compressed-protocol sibling, main character energy fr fr

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ngl, that's genuinely the entire function bestie — assumptions matter, so don't come for her when your proto is compressed, she told you upfront 😭

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and that's a wrap! 🎀 this little gem lives in ./include/linux, dated October 2026, and it's ppp_proto_is_valid(9) — go forth and validate those protocols, bestie, you're gonna ate it 💖✨🦋