Merge pull request #12346 from poettering/accept-flush

socket-util: make sure accept_flush() doesn't hang on EOPNOTSUPP

src/basic/socket-util.c

@@ -1225,9 +1225,22 @@ int flush_accept(int fd) {
                 .fd = fd,
                 .events = POLLIN,
         };
-        int r;
+        int r, b;
+        socklen_t l = sizeof(b);
 
-        /* Similar to flush_fd() but flushes all incoming connection by accepting them and immediately closing them. */
+        /* Similar to flush_fd() but flushes all incoming connection by accepting them and immediately
+         * closing them.  */
+
+        if (getsockopt(fd, SOL_SOCKET, SO_ACCEPTCONN, &b, &l) < 0)
+                return -errno;
+
+        assert(l == sizeof(b));
+        if (!b) /* Let's check if this is a socket accepting connections before calling accept(). That's
+                 * because accept4() can return EOPNOTSUPP in the fd we are called on is not a listening
+                 * socket, or in case the incoming TCP connection transiently triggered that (see accept(2)
+                 * man page for details). The latter case is a transient error we should continue looping
+                 * on. The former case however is fatal. */
+                return -ENOTTY;
 
         for (;;) {
                 int cfd;

src/test/test-socket-util.c

@@ -810,6 +810,67 @@ static void test_send_emptydata(void) {
         assert_se(fd == -999);
 }
 
+static void test_flush_accept(void) {
+        _cleanup_close_ int listen_stream = -1, listen_dgram = -1, listen_seqpacket = 1, connect_stream = -1, connect_dgram = -1, connect_seqpacket = -1;
+        static const union sockaddr_union sa = { .un.sun_family = AF_UNIX };
+        union sockaddr_union lsa;
+        socklen_t l;
+
+        listen_stream = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        assert_se(listen_stream >= 0);
+
+        listen_dgram = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        assert_se(listen_dgram >= 0);
+
+        listen_seqpacket = socket(AF_UNIX, SOCK_SEQPACKET|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        assert_se(listen_seqpacket >= 0);
+
+        assert_se(flush_accept(listen_stream) < 0);
+        assert_se(flush_accept(listen_dgram) < 0);
+        assert_se(flush_accept(listen_seqpacket) < 0);
+
+        assert_se(bind(listen_stream, &sa.sa, sizeof(sa_family_t)) >= 0);
+        assert_se(bind(listen_dgram, &sa.sa, sizeof(sa_family_t)) >= 0);
+        assert_se(bind(listen_seqpacket, &sa.sa, sizeof(sa_family_t)) >= 0);
+
+        assert_se(flush_accept(listen_stream) < 0);
+        assert_se(flush_accept(listen_dgram) < 0);
+        assert_se(flush_accept(listen_seqpacket) < 0);
+
+        assert_se(listen(listen_stream, SOMAXCONN) >= 0);
+        assert_se(listen(listen_dgram, SOMAXCONN) < 0);
+        assert_se(listen(listen_seqpacket, SOMAXCONN) >= 0);
+
+        assert_se(flush_accept(listen_stream) >= 0);
+        assert_se(flush_accept(listen_dgram) < 0);
+        assert_se(flush_accept(listen_seqpacket) >= 0);
+
+        connect_stream = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        assert_se(connect_stream >= 0);
+
+        connect_dgram = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        assert_se(connect_dgram >= 0);
+
+        connect_seqpacket = socket(AF_UNIX, SOCK_SEQPACKET|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
+        assert_se(connect_seqpacket >= 0);
+
+        l = sizeof(lsa);
+        assert_se(getsockname(listen_stream, &lsa.sa, &l) >= 0);
+        assert_se(connect(connect_stream, &lsa.sa, l) >= 0);
+
+        l = sizeof(lsa);
+        assert_se(getsockname(listen_dgram, &lsa.sa, &l) >= 0);
+        assert_se(connect(connect_dgram, &lsa.sa, l) >= 0);
+
+        l = sizeof(lsa);
+        assert_se(getsockname(listen_seqpacket, &lsa.sa, &l) >= 0);
+        assert_se(connect(connect_seqpacket, &lsa.sa, l) >= 0);
+
+        assert_se(flush_accept(listen_stream) >= 0);
+        assert_se(flush_accept(listen_dgram) < 0);
+        assert_se(flush_accept(listen_seqpacket) >= 0);
+}
+
 int main(int argc, char *argv[]) {
         test_setup_logging(LOG_DEBUG);
 
@@ -843,6 +904,7 @@ int main(int argc, char *argv[]) {
         test_receive_nopassfd();
         test_send_nodata_nofd();
         test_send_emptydata();
+        test_flush_accept();
 
         return 0;
 }

src/udev/udev-rules.c

@@ -2442,7 +2442,7 @@ int udev_rules_apply_to_event(
                 case TK_A_RUN_BUILTIN:
                 case TK_A_RUN_PROGRAM: {
                         _cleanup_free_ char *cmd = NULL;
-                        
+
                         if (event->run_final)
                                 break;
                         if (cur->key.op == OP_ASSIGN_FINAL)