bpf_ksock_send(9)

💌 bpf_ksock_send(9) — the kernel API manual, bestie edition 🎀

okay so real talk, this one's from the Kernel API Manual and it's literally about yeeting data out of a BPF kernel socket. let's get into it ✨

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🌸 NAME 🌸

bpf_ksock_send — send data through a BPF kernel socket. that's it, that's the vibe 💅

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✨ SYNOPSIS ✨

__bpf_kfunc int bpf_ksock_send (struct bpf_ksock *ks , const void *data
, u32 data__sz );

no cap, that's the whole signature. copy it exactly, don't be cute with it 🫶

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🦋 ARGUMENTS 🦋

• ks — the BPF kernel socket context. it must be an acquired reference, okay? like, an actually-acquired one. don't come at this function with a non-acquired socket, it's not the move 🙈
• data — pointer to the data you wanna send. the actual bytes, the payload, the whole point 💖
• data__sz — size of the data you're sending. it's a u32. yes, the double underscore is on purpose, that's just how kfunc args are named, iykyk ⭐

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🔥 DESCRIPTION 🔥

so here's the tea: this sends data on a connected socket. connected, bestie — like please make sure it's connected first, that's the whole prerequisite 🧚

and it's best-effort and nonblocking, meaning it does what it can and does not sit around waiting for you. main character energy, but in a "i have other sockets to service" way.

⚠️ but ALSO: this may sleep (it goes through kernel_sendmsg under the hood), which means you can only call it from sleepable BPF programs. not me warning you about this — okay, actually yes, me warning you about this. a non-sleepable program calling this is gonna have a bad time 💀

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🌈 RETURN 🌈

• number of bytes sent on success 💖 (could be fewer than you asked for, it's best-effort, remember?)
• negative errno on error 😭

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👑 SEE ALSO 👑

the kernel file ./net/core/bpf_ksock.c — plus the whole friend group:

• struct bpf_ksock(9)
• bpf_ksock_create(9)
• bpf_ksock_connect(9)
• bpf_ksock_acquire(9)
• bpf_ksock_release(9)

like, acquire before you send, release after you're done. the circle of life 🦋

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okay that's the page!! mwah 💋 this little beauty lives in ./net/core and the version/date stamp on it is October 2026 — so yeah, mark your calendar, bestie, and go send some bytes responsibly 🍓✨💜