passt-repair: Simplify construction of Unix path from inotify

When passt-repair is invoked with a directory name, it waits for a Unix
socket to appear in that directory.  We need to build the Unix path name
from the given directory, plus the stem file name from the inotify event.

Currently, we build that path into a temporary buffer of size PATH_MAX,
then move it into the smaller buffer inside the Unix sockaddr.  There's no
particular reason for this two step process, we can build the address
directly within the sockaddr_un.  This will give a slightly different error
if the constructed path exceeds the maximum length of a Unix address, but
it will fail either way so it doesn't really matter.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/passt-repair.c b/passt-repair.c
index 980b0b0..d4c8ce9 100644
--- a/passt-repair.c
+++ b/passt-repair.c
@@ -64,10 +64,9 @@ static int wait_for_socket(struct sockaddr_un *a, const char *dir,
 	char buf[sizeof(struct inotify_event) + NAME_MAX + 1]
 		__attribute__ ((aligned(__alignof__(struct inotify_event))));
 	const struct inotify_event *ev = NULL;
-	char path[PATH_MAX + 1];
 	bool found = false;
+	int fd, ret;
 	ssize_t n;
-	int fd;
 
 	if ((fd = inotify_init1(IN_CLOEXEC)) < 0) {
 		fprintf(stderr, "inotify_init1: %i\n", errno);
@@ -113,13 +112,15 @@ static int wait_for_socket(struct sockaddr_un *a, const char *dir,
 		_exit(1);
 	}
 
-	snprintf(path, sizeof(path), "%s/%s", dir, ev->name);
-	if ((stat(path, sb))) {
-		fprintf(stderr, "Can't stat() %s: %i\n", path, errno);
+	ret = snprintf(a->sun_path, sizeof(a->sun_path), "%s/%s",
+		       dir, ev->name);
+
+	if ((stat(a->sun_path, sb))) {
+		fprintf(stderr, "Can't stat() %s: %i\n", a->sun_path, errno);
 		_exit(1);
 	}
 
-	return snprintf(a->sun_path, sizeof(a->sun_path), "%s", path);
+	return ret;
 }
 
 /**