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unix: make uv_guess_handle work properly for AIX

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On AIX, the getsockname API does not operate on the UNIX domain sockets
Please see: https://www-01.ibm.com/support/knowledgecenter/ssw_aix_61/
com.ibm.aix.commtrf2/getsockname.htm

This means that the internal helper routine uv_guess_handle in tty.c
fails in AIX, for common use cases.

There is no direct API support which helps identifying a UNIX domain
socket in AIX. getpeername() retrieves the information pertinent to
connected UNIX domain socket pairs, and using getpeername where
getsockname fails was a good workaround. However, there are edge cases
where one end of a socketpair comes for introspection while the other
end has been closed, which causes getpeername to fail.

A better solution is derived based on these facts:

1.getsockname() on a broken / un-broken socketpair does not actually
fail with -1, instead it returns 0. However, the API does not modify
the socketaddr structure passed to it, with the socket information.

2.This behavior of getsockname is observed only for UNIX domain socket,
among all possible types of sockets which I tested - ~30 of them.

So a practical and stable workaround for AIX is to return
UV_UNKNOWN_HANDLE if getsockname fails.  If it passes and the length
of the structure returned is 0 then we know that the type is AF_UNIX
and return UV_NAMED_PIPE , otherwise we inspect in the same way as for
other platforms to derive the type.

PR-URL: https://github.com/libuv/libuv/pull/539
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
This commit is contained in:
Gireesh Punathil 2015-09-22 07:37:48 -04:00 committed by Saúl Ibarra Corretgé
parent 25c369d4cf
commit 25506bb331
1 changed files with 9 additions and 0 deletions
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9
src/unix/tty.c
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@ -236,6 +236,15 @@ uv_handle_type uv_guess_handle(uv_file file) {
return UV_UDP;
if (type == SOCK_STREAM) {
#if defined(_AIX)
/* on AIX the getsockname call returns an empty sa structure
* for sockets of type AF_UNIX. For all other types it will
* return a properly filled in structure.
*/
if (len == 0)
return UV_NAMED_PIPE;
#endif /* defined(_AIX) */
if (sa.sa_family == AF_INET || sa.sa_family == AF_INET6)
return UV_TCP;
if (sa.sa_family == AF_UNIX)