socket-util: add new sockaddr_un_unlink() helper

The helper is supposed to properly handle cases where .sun_path does not
contain a NUL byte, and thus copies out the path suffix a NUL as
necessary.

This also reworks the more specific socket_address_unlink() to be a
wrapper around the more generic sockaddr_un_unlink()

src/basic/socket-util.c

@@ -747,21 +747,6 @@ int socknameinfo_pretty(union sockaddr_union *sa, socklen_t salen, char **_ret)
         return 0;
 }
 
-int socket_address_unlink(SocketAddress *a) {
-        assert(a);
-
-        if (socket_address_family(a) != AF_UNIX)
-                return 0;
-
-        if (a->sockaddr.un.sun_path[0] == 0)
-                return 0;
-
-        if (unlink(a->sockaddr.un.sun_path) < 0)
-                return -errno;
-
-        return 1;
-}
-
 static const char* const netlink_family_table[] = {
         [NETLINK_ROUTE] = "route",
         [NETLINK_FIREWALL] = "firewall",
@@ -1246,3 +1231,27 @@ int socket_ioctl_fd(void) {
 
         return fd;
 }
+
+int sockaddr_un_unlink(const struct sockaddr_un *sa) {
+        const char *p, * nul;
+
+        assert(sa);
+
+        if (sa->sun_family != AF_UNIX)
+                return -EPROTOTYPE;
+
+        if (sa->sun_path[0] == 0) /* Nothing to do for abstract sockets */
+                return 0;
+
+        /* The path in .sun_path is not necessarily NUL terminated. Let's fix that. */
+        nul = memchr(sa->sun_path, 0, sizeof(sa->sun_path));
+        if (nul)
+                p = sa->sun_path;
+        else
+                p = memdupa_suffix0(sa->sun_path, sizeof(sa->sun_path));
+
+        if (unlink(p) < 0)
+                return -errno;
+
+        return 1;
+}

src/basic/socket-util.h

@@ -71,7 +71,12 @@ int socket_address_parse_and_warn(SocketAddress *a, const char *s);
 int socket_address_parse_netlink(SocketAddress *a, const char *s);
 int socket_address_print(const SocketAddress *a, char **p);
 int socket_address_verify(const SocketAddress *a) _pure_;
-int socket_address_unlink(SocketAddress *a);
+
+int sockaddr_un_unlink(const struct sockaddr_un *sa);
+
+static inline int socket_address_unlink(const SocketAddress *a) {
+        return socket_address_family(a) == AF_UNIX ? sockaddr_un_unlink(&a->sockaddr.un) : 0;
+}
 
 bool socket_address_can_accept(const SocketAddress *a) _pure_;