chg: let hgc_open support long path
"sizeof(sun_path)" is too small. Use the chdir trick to support long socket
path, like "mercurial.util.bindunixsocket".
It's useful for cases where TMPDIR is long. Modern OS X rewrites TMPDIR to a
long value. And we probably want to use XDG_RUNTIME_DIR [2] for Linux.
The approach is a bit different from the previous plan, where we will have
hgc_openat and pass cmdserveropts.sockdirfd to it. That's because the
current change is easier: chg has to pass a full path to "hg" as the
"--address" parameter. There is no "--address-basename" or "--address-dirfd"
flags. The next patch will remove "sockdirfd".
Note: It'd be nice if we can use a native "connectat" implementation.
However, that's not available everywhere. Some platform (namely FreeBSD)
does support it, but the implementation has bugs so it cannot be used [2].
[1]: https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
[2]: https://www.mercurial-scm.org/pipermail/mercurial-devel/2016-April/082892.html
--- a/contrib/chg/hgclient.c Sat Dec 24 15:38:27 2016 -0500
+++ b/contrib/chg/hgclient.c Fri Dec 23 16:37:00 2016 +0000
@@ -425,10 +425,43 @@
struct sockaddr_un addr;
addr.sun_family = AF_UNIX;
- strncpy(addr.sun_path, sockname, sizeof(addr.sun_path));
+
+ /* use chdir to workaround small sizeof(sun_path) */
+ int bakfd = -1;
+ const char *basename = sockname;
+ {
+ const char *split = strrchr(sockname, '/');
+ if (split && split != sockname) {
+ if (split[1] == '\0')
+ abortmsg("sockname cannot end with a slash");
+ size_t len = split - sockname;
+ char sockdir[len + 1];
+ memcpy(sockdir, sockname, len);
+ sockdir[len] = '\0';
+
+ bakfd = open(".", O_DIRECTORY);
+ if (bakfd == -1)
+ abortmsgerrno("cannot open cwd");
+
+ int r = chdir(sockdir);
+ if (r != 0)
+ abortmsgerrno("cannot chdir %s", sockdir);
+
+ basename = split + 1;
+ }
+ }
+ if (strlen(basename) >= sizeof(addr.sun_path))
+ abortmsg("sockname is too long: %s", basename);
+ strncpy(addr.sun_path, basename, sizeof(addr.sun_path));
addr.sun_path[sizeof(addr.sun_path) - 1] = '\0';
+ /* real connect */
int r = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
+ if (bakfd != -1) {
+ fchdirx(bakfd);
+ close(bakfd);
+ }
+
if (r < 0) {
close(fd);
if (errno == ENOENT || errno == ECONNREFUSED)