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Add better support for unnamed unix socket addrs#1857

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bors[bot] merged 4 commits intonix-rust:masterfrom
stevenengler:unnamed-unix-sockets
Nov 21, 2022
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Add better support for unnamed unix socket addrs#1857
bors[bot] merged 4 commits intonix-rust:masterfrom
stevenengler:unnamed-unix-sockets

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@stevenengler stevenengler commented Nov 7, 2022 •
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This adds the following 2 functions/methods: UnixAddr::new_unnamed and UnixAddr::is_unnamed.

Closes #1585

unix(7) on Linux:

unnamed: A stream socket that has not been bound to a pathname using bind(2) has no name. Likewise, the two sockets created by socketpair(2) are unnamed. When the address of an unnamed socket is returned, its length is sizeof(sa_family_t), and sun_path should not be inspected.

Edit: This currently isn't working on BSD, but I see why. Will fix it shortly.

@stevenengler stevenengler force-pushed the unnamed-unix-sockets branch 5 times, most recently from b1af529 to 60f17d7 Compare November 7, 2022 23:40
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stevenengler commented Nov 7, 2022 •
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I decided to only enable these on Linux/Android, since unnamed unix sockets seem to behave differently on FreeBSD and I can't find any documentation for its behaviour. For example when running getsockname() on the fd returned from socketpair(), it returns an addrlen of 16 bytes while SUN_LEN(&addr) returns 2. I'm not sure that the existing code in UnixAddrKind::get() handles this correctly either on FreeBSD.

The current test failures seem to be unrelated, probably from a new clippy version.

asomers
asomers requested changes Nov 19, 2022
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I think that defining this for Linux only is appropriate, because AFAIK no BSD OS documents such a thing. But don't forget the CHANGELOG. Also, I'd like to merge this before PR #1871.

Comment thread test/sys/test_socket.rs Outdated

let addr_1: UnixAddr = getsockname(fd_1).expect("getsockname failed");
assert!(addr_1.is_unnamed());
assert_eq!(addr_1, UnixAddr::new_unnamed());
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Is this part guaranteed to work, according to any Linux documentation, or is it just luck? I'm not sure we should have this assertion.

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Linux says "When the address of an unnamed socket is returned, its length is sizeof(sa_family_t)", so the only possible unnamed unix socket address it could return would be sockaddr_un { sun_family: AF_UNIX, ... } with length 2. But I agree that the documentation around this still isn't great, so I removed this assertion.

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asomers commented Nov 19, 2022

Also, rebasing should fix the CI failures.

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LGTM, but I violated my own request and merged #1871 first. So I'll fix the subtle conflict myself.

bors r+

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bors bot commented Nov 21, 2022

Build succeeded:

@bors bors bot merged commit 79f04fb into nix-rust:master Nov 21, 2022
@stevenengler stevenengler deleted the unnamed-unix-sockets branch November 21, 2022 18:07
asomers added a commit to asomers/nix that referenced this pull request Nov 21, 2022
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Use the new UnixAddr::new_unnamed in the unit tests
59c21f7 
Use it in the from_sockaddr_un_abstract_unnamed test.  That test and
this method were introduced by PRs nix-rust#1871 and nix-rust#1857, which crossed each
other.
@asomers asomers mentioned this pull request Nov 21, 2022
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bors bot added a commit that referenced this pull request Nov 21, 2022
@bors @asomers
Merge #1880
8522191 
1880: Use the new UnixAddr::new_unnamed in the unit tests r=rtzoeller a=asomers

Use it in the from_sockaddr_un_abstract_unnamed test.  That test and this method were introduced by PRs #1871 and #1857, which crossed each other.

Co-authored-by: Alan Somers <asomers@gmail.com>
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No longer able to create an unnamed UnixAddr as of nix 23.0

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