csum_partial(9)

💖 NAME 💖

okay bestie, welcome to csum_partial(9) — that's the page, and we're chilling in the Kernel API Manual. This one is literally about computing an internet checksum. no cap ✨

🎀 SYNOPSIS 🎀

__wsum csum_partial (const void *buff , int len , __wsum sum );

🦋 ARGUMENTS 🦋

• buff — the buffer to be checksummed. yes, this is the thing getting the checksum treatment 💅
• len — length of buffer.
• sum — the initial sum to be added in (32bit unfolded). it comes preloaded, bestie 🫶

🔥 RETURN 🔥

You get back the 32bit unfolded internet checksum of the buffer. Quick heads-up though: before filling it in, it needs to be csum_fold'ed — that step is mandatory, not a vibe 😭

Also, buff should be aligned to a 64bit boundary if possible. alignment is kinda giving main character energy here 👑

🌈 SEE ALSO 🌈

• Kernel file ./arch/x86/include/asm/checksum_64.h
• csum_fold(9)
• ip_fast_csum(9)
• csum_tcpudp_nofold(9)
• csum_tcpudp_magic(9)
• ip_compute_csum(9)
• csum_ipv6_magic(9)

go read these too, iykyk 🫶💜

source/version: ./arch/x86/include/asm — dated October 2026 — catch you later bestie, stay folded 💅🎀