https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=9e573ba50f129bff7b6e1be10cf4bbcb70f1efdd
commit 9e573ba50f129bff7b6e1be10cf4bbcb70f1efdd Author: Mark Geisert <[email protected]> Date: Mon Dec 7 02:29:36 2020 -0800 Cygwin: Allow to set SO_PEERCRED zero (v2) The existing code errors as EINVAL any attempt to set a value for SO_PEERCRED via setsockopt() on an AF_UNIX/AF_LOCAL socket. But to enable the workaround set_no_getpeereid behavior for Python one has to be able to set SO_PEERCRED to zero. Ergo, this patch. Python has no way to specify a NULL pointer for 'optval'. This v2 of patch allows the original working (i.e., allow NULL,0 for optval,optlen to mean turn off SO_PEERCRED) in addition to the new working described above. The sense of the 'if' stmt is reversed for readability. Diff: --- winsup/cygwin/fhandler_socket_local.cc | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/winsup/cygwin/fhandler_socket_local.cc b/winsup/cygwin/fhandler_socket_local.cc index c94bf828f..964f3e819 100644 --- a/winsup/cygwin/fhandler_socket_local.cc +++ b/winsup/cygwin/fhandler_socket_local.cc @@ -1430,10 +1430,14 @@ fhandler_socket_local::setsockopt (int level, int optname, const void *optval, FIXME: In the long run we should find a more generic solution which doesn't require a blocking handshake in accept/connect to exchange SO_PEERCRED credentials. */ - if (optval || optlen) - set_errno (EINVAL); - else + /* Temporary: Allow SO_PEERCRED to only be zeroed. Two ways to + accomplish this: pass NULL,0 for optval,optlen; or pass the + address,length of an '(int) 0' set up by the caller. */ + if ((!optval && !optlen) || + (optlen == (socklen_t) sizeof (int) && !*(int *) optval)) ret = af_local_set_no_getpeereid (); + else + set_errno (EINVAL); return ret; case SO_REUSEADDR:
