io_uring_pre...d_getsockname(3)

💅 io_uring_prep_cmd_getsockname — bestie edition

okay so this is a page from the liburing Manual, and it's all about io_uring_prep_cmd_getsockname(3) — yes that's the whole name, it's a long one, she's dramatic, we love her for it 🎀

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✨ NAME ✨

io_uring_prep_cmd_getsockname — prepare a getsockname or getpeername request

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🌸 SYNOPSIS 🌸

#include <sys/socket.h>
#include <liburing.h>

void io_uring_prep_cmd_getsockname(struct io_uring_sqe *sqe,
                                   int fd,
                                   struct sockaddr *sockaddr,
                                   socklen_t *sockaddr_len,
                                   int peer);

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🦋 DESCRIPTION 🦋

so io_uring_prep_cmd_getsockname(3) is the girl who prepares a getsockname/getpeername request. she doesn't do the whole thing herself, she just sets it up. main character energy but make it delegation 💅

the submission queue entry sqe gets set up to fetch the locally bound address — or the peer address — of the socket file descriptor pointed at by sockfd.

the sockaddr parameter points to a region of size sockaddr_len where the output gets written. and sockaddr_len? the kernel modifies it on return to tell you how many bytes were actually written. so yeah, she comes back changed, that's normal, that's the vibe. ✨

which address you get depends on peer, no cap:

• if peer is set to 0 → you get the locally bound address
• if peer is set to 1 → you get the peer address

this function prepares an async getsockname(2) or getpeername(2) request. go read those man pages for the deets, they have the lore 🫶

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💖 RETURN VALUE 💖

None. that's it. nothing. she returns void and she's at peace with it 🙈

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💀 ERRORS 💀

the res field of the CQE is where the result lives. check the related man page for what values it could be, bestie.

and now the important part, listen up 🔥 — where synchronous system calls would return -1 on failure and set errno to the actual error value, io_uring never uses errno. never ever. instead it returns the negated errno directly in the CQE res field. that's just how she operates.

⚠️ also, and this is the plot twist: differently from the equivalent system calls, if you try to use this operation on a non-socket file descriptor, the CQE error result is ENOTSUP instead of ENOSOCK. so like, not the error you'd expect. lowkey iconic of her to be different.

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🌈 SEE ALSO 🌈

• io_uring_get_sqe(3)
• io_uring_submit(3)
• getsockname(2)
• getpeername(2)

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and that's the whole page bestie, we ate and left no crumbs 🍓✨

this one's from liburing-2.13, dated December 3, 2025 — so yeah, fresh off the press, mwah 💋 👑