From patchwork Mon Apr  4 02:30:53 2016
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Subject: [6,of,7] chg: use relative path at connect
From: Jun Wu <quark@fb.com>
X-Patchwork-Id: 14323
Message-Id: <f7c6cfae4dba1c48a63b.1459737053@x1c>
To: <mercurial-devel@mercurial-scm.org>
Date: Mon, 4 Apr 2016 03:30:53 +0100

# HG changeset patch
# User Jun Wu <quark@fb.com>
# Date 1459736917 -3600
#      Mon Apr 04 03:28:37 2016 +0100
# Node ID f7c6cfae4dba1c48a63bdea1b9aa816e7f634d02
# Parent  f5414d2b4f32431a251029ebf46f48efdd9f013c
chg: use relative path at connect

We have made chgserver use relative path at bind(), now do the same change to
the client at connect().

diff --git a/contrib/chg/hgclient.c b/contrib/chg/hgclient.c
--- a/contrib/chg/hgclient.c
+++ b/contrib/chg/hgclient.c
@@ -424,12 +424,36 @@
 	if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) < 0)
 		abortmsg("cannot set flags of socket (errno = %d)", errno);
 
+	/* use relative (shorter) path at connect() if possible. it is helpful
+	 * because sizeof(addr.sun_path) can be very small (usually 108). */
+	int bakwdfd = -1;
+	const char *lastsep = strrchr(sockname, '/');
+	if (lastsep) {
+		bakwdfd = open(".", O_DIRECTORY);
+		size_t len = lastsep - sockname;
+		char dir[len + 1];
+		memcpy(dir, sockname, len);
+		if (chdir(dir) != 0)
+			abortmsg("cannot chdir (errno = %d)", errno);
+		sockname = lastsep + 1;
+	}
+
 	struct sockaddr_un addr;
 	addr.sun_family = AF_UNIX;
+	addr.sun_path[sizeof(addr.sun_path) - 1] = '\0';
 	strncpy(addr.sun_path, sockname, sizeof(addr.sun_path));
-	addr.sun_path[sizeof(addr.sun_path) - 1] = '\0';
+	if (addr.sun_path[sizeof(addr.sun_path) - 1] != '\0')
+		abortmsg("sockname %s is too long", sockname);
 
 	int r = connect(fd, (struct sockaddr *)&addr, sizeof(addr));
+
+	/* restore workdir right after connect() */
+	if (bakwdfd != -1) {
+		if (fchdir(bakwdfd) != 0)
+			abortmsg("cannot chdir back (errno = %d)", errno);
+		close(bakwdfd);
+	}
+
 	if (r < 0) {
 		close(fd);
 		if (errno == ENOENT || errno == ECONNREFUSED)