Use non-blocking connect() for AF_UNIX sockets to ensure we don't stall

common/common.c

@@ -5174,6 +5174,53 @@ char *xstrdup(const char *string)
 	return p;
 }
 
+/* Try to connect to addr, using select() for timeout since AF_UNIX won't timeout normally */
+#ifndef WIN32
+int select_connect(int fd, const struct sockaddr_un *addr, size_t addrlen, const time_t d_sec, const suseconds_t d_usec)
+{
+	int rc;
+	int err = 0;
+	int flags = fcntl(fd, F_GETFL, 0);
+	fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+
+	rc = connect(fd, (const struct sockaddr *)addr, addrlen);
+	if (rc == -1 && errno != EINPROGRESS) {
+		err = errno;
+	} else if (rc == -1) {
+		fd_set w_fds;
+		fd_set e_fds;
+		struct timeval tv;
+
+		FD_ZERO(&w_fds);
+		FD_SET(fd, &w_fds);
+		FD_ZERO(&e_fds);
+		FD_SET(fd, &e_fds);
+
+		tv.tv_sec = d_sec;
+		tv.tv_usec = d_usec;
+
+		rc = select(fd + 1, NULL, &w_fds, &e_fds, &tv);
+
+		if (rc < 0) {
+			err = errno;
+		} else if (rc == 0) {
+			err = ETIMEDOUT;
+		} else {
+			socklen_t len = sizeof(err);
+			getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &len);
+		}
+	}
+
+	fcntl(fd, F_SETFL, flags);
+
+	if (err != 0) {
+		errno = err;
+		return -1;
+	}
+	return 0;
+}
+#endif
+
 /* Read up to buflen bytes from fd and return the number of bytes
    read. If no data is available within d_sec + d_usec, return 0.
    On error, a value < 0 is returned (errno indicates error). */

drivers/upsdrvquery.c

@@ -81,7 +81,7 @@ udq_pipe_conn_t *upsdrvquery_connect(const char *sockfn) {
 		return NULL;
 	}
 
-	if (connect(conn->sockfd, (struct sockaddr *) &sa, sizeof(sa)) < 0) {
+	if (select_connect(conn->sockfd, &sa, sizeof(sa), 1, 0) < 0) {
 		if (nut_debug_level > 0 || nut_upsdrvquery_debug_level >= NUT_UPSDRVQUERY_DEBUG_LEVEL_CONNECT)
 			upslog_with_errno(LOG_ERR, "connect to driver socket at %s", sockfn);
 		close(conn->sockfd);

include/common.h

@@ -67,6 +67,7 @@
 
 #ifndef WIN32
 # include <syslog.h>
+# include <sys/un.h>
 #else	/* WIN32 */
 # include <winsock2.h>
 # include <windows.h>
@@ -754,6 +755,7 @@ int match_regex_hex(const regex_t *preg, const int n);
 
 /* Note: different method signatures instead of TYPE_FD_SER due to "const" */
 #ifndef WIN32
+int select_connect(int fd, const struct sockaddr_un *addr, size_t addrlen, const time_t d_sec, const suseconds_t d_usec);
 ssize_t select_read(const int fd, void *buf, const size_t buflen, const time_t d_sec, const suseconds_t d_usec);
 ssize_t select_write(const int fd, const void *buf, const size_t buflen, const time_t d_sec, const suseconds_t d_usec);
 #else	/* WIN32 */

server/sstate.c

@@ -215,9 +215,10 @@ TYPE_FD sstate_connect(upstype_t *ups)
 		return ERROR_FD;
 	}
 
-	ret = connect(fd, (struct sockaddr *) &sa, sizeof(sa));
+	ret = select_connect(fd, &sa, sizeof(sa), 1, 0);
 
 	if (ret < 0) {
+		int err = errno;
 		time_t	now;
 
 		if (strstr(sa.sun_path, "/")) {
@@ -237,6 +238,8 @@ TYPE_FD sstate_connect(upstype_t *ups)
 			return ERROR_FD;
 
 		ups->last_connfail = now;
+		/* restore errno for logging */
+		errno = err;
 		if (strstr(ups->fn, "/")) {
 			upslog_with_errno(LOG_ERR, "Can't connect to UPS [%s] (%s)",
 				ups->name, ups->fn);