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gh-128881: Do not ignore address and flags parameters in socket.{send,recv}_fds #128882

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@GalaxySnail GalaxySnail commented Jan 15, 2025

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I have no idea what's happening on macOS. Should we just skip it on macOS?

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Zheaoli commented Jan 16, 2025

MSG_PEEK may got different action on macOS/FreeBSD, let's figure it out.

BTW, we can skip the macOS test first

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Can we also have a test that combine both address and flags as well for send_fds please? and see if we can have test coverage for Windows (just using a 0 flag for instance would be sufficient).

According to https://docs.python.org/3/library/socket.html#socket.send_fds, send_fds and recv_fds are is available on Windows and Unix, so we should be able to have tests for them as well.

@picnixz picnixz changed the title gh-128881: Fix address and flags for send_fds/recv_fds gh-128881: Do not ignore address and flags parameters in socket.{send,recv}_fds Jan 17, 2025
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
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GalaxySnail commented Jun 2, 2025

I found that FreeBSD doesn't seem to support receiving only 1 file descriptor with recvmsg. Using CMSG_LEN(sizeof(int)) leads to MSG_CTRUNC, while CMSG_LEN(2 * sizeof(int)) is required to successfully receive a single file descriptor.

Here is a POC: https://fars.ee/Ih-8/c

$ curl https://fars.ee/Ih-8 -o foo.c
$ cc -Wall -Wextra -Wpedantic -std=c17 foo.c && truss -o out.txt ./a.out && ggrep -E 'sendmsg|recvmsg' out.txt
sendmsg(3,{NULL,0,[{"Hello world!",12}],1,{{level=SOL_SOCKET,type=SCM_RIGHTS,data={0x01,0x00,0x00,0x00}}},20,0},0) = 12 (0xc)
recvmsg(4,{NULL,0,[{"Hello world!",12}],1,{},0,MSG_CTRUNC},0) = 12 (0xc)
$ gsed -i 's|fds\[\] = {1}|fds[] = {1, 2}|' foo.c
$ cc -Wall -Wextra -Wpedantic -std=c17 foo.c && truss -o out.txt ./a.out && ggrep -E 'sendmsg|recvmsg' out.txt
sendmsg(3,{NULL,0,[{"Hello world!",12}],1,{{level=SOL_SOCKET,type=SCM_RIGHTS,data={0x01,0x00,0x00,0x00,0x02,0x00,0x00,0x00}}},24,0},0) = 12 (0xc)
recvmsg(4,{NULL,0,[{"Hello world!",12}],1,{{level=SOL_SOCKET,type=SCM_RIGHTS,data={0x05,0x00,0x00,0x00,0x06,0x00,0x00,0x00}}},24,0},0) = 12 (0xc)

@GalaxySnail GalaxySnail requested a review from picnixz June 2, 2025 08:18
GalaxySnail and others added 3 commits June 2, 2025 18:46
update comments

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
@GalaxySnail GalaxySnail requested a review from picnixz June 2, 2025 13:41
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3 participants