libbb: move netlink socket binding to the utility function

function                                             old     new   delta
create_and_bind_to_netlink                             -     134    +134
ifplugd_main                                        1117    1052     -65
uevent_main                                          399     306     -93
mdev_main                                            314     215     -99
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/3 up/down: 134/-257)         Total: -123 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 18 insertions, 47 deletions

diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index 88c82b6fb..9cb3586f1 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -1225,28 +1225,16 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
 		/*
 		 * Daemon mode listening on uevent netlink socket.
 		 */
-		struct sockaddr_nl sa;
 		int fd;
 
-//TODO: reuse same code in uevent
-		// Subscribe for UEVENT kernel messages
-		sa.nl_family = AF_NETLINK;
-		sa.nl_pad = 0;
-		sa.nl_pid = getpid();
-		sa.nl_groups = 1 << 0;
-		fd = xsocket(AF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
-		xbind(fd, (struct sockaddr *) &sa, sizeof(sa));
-		close_on_exec_on(fd);
-
-		// Without a sufficiently big RCVBUF, a ton of simultaneous events
-		// can trigger ENOBUFS on read, which is unrecoverable.
-		// Reproducer:
-		//	mdev -d
-		// 	find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
-		//
-		// SO_RCVBUFFORCE (root only) can go above net.core.rmem_max sysctl
-		setsockopt_SOL_SOCKET_int(fd, SO_RCVBUF,      RCVBUF);
-		setsockopt_SOL_SOCKET_int(fd, SO_RCVBUFFORCE, RCVBUF);
+		/* Subscribe for UEVENT kernel messages */
+		/* Without a sufficiently big RCVBUF, a ton of simultaneous events
+		 * can trigger ENOBUFS on read, which is unrecoverable.
+		 * Reproducer:
+		 *	mdev -d
+		 *	find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
+		 */
+		fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, 1 << 0, RCVBUF);
 
 		/*
 		 * Make inital scan after the uevent socket is alive and
diff --git a/util-linux/uevent.c b/util-linux/uevent.c
index 761743f45..2f8990ed9 100644
--- a/util-linux/uevent.c
+++ b/util-linux/uevent.c
@@ -46,37 +46,19 @@ enum { RCVBUF = 2 * 1024 * 1024 };
 int uevent_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int uevent_main(int argc UNUSED_PARAM, char **argv)
 {
-	struct sockaddr_nl sa;
 	int fd;
 
 	INIT_G();
 
 	argv++;
 
-	// Subscribe for UEVENT kernel messages
-	sa.nl_family = AF_NETLINK;
-	sa.nl_pad = 0;
-	sa.nl_pid = getpid();
-	sa.nl_groups = 1 << 0;
-	fd = xsocket(AF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
-	xbind(fd, (struct sockaddr *) &sa, sizeof(sa));
-	close_on_exec_on(fd);
-
+	// Subscribe for UEVENT kernel messages.
 	// Without a sufficiently big RCVBUF, a ton of simultaneous events
 	// can trigger ENOBUFS on read, which is unrecoverable.
 	// Reproducer:
 	//	uevent mdev &
 	// 	find /sys -name uevent -exec sh -c 'echo add >"{}"' ';'
-	//
-	// SO_RCVBUFFORCE (root only) can go above net.core.rmem_max sysctl
-	setsockopt_SOL_SOCKET_int(fd, SO_RCVBUF,      RCVBUF);
-	setsockopt_SOL_SOCKET_int(fd, SO_RCVBUFFORCE, RCVBUF);
-	if (0) {
-		int z;
-		socklen_t zl = sizeof(z);
-		getsockopt(fd, SOL_SOCKET, SO_RCVBUF, &z, &zl);
-		bb_error_msg("SO_RCVBUF:%d", z);
-	}
+	fd = create_and_bind_to_netlink(NETLINK_KOBJECT_UEVENT, /*groups:*/ 1 << 0, RCVBUF);
 
 	for (;;) {
 		char *netbuf;
@@ -118,14 +100,15 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
 		}
 		env[idx] = NULL;
 
-		idx = 0;
-		while (env[idx])
-			putenv(env[idx++]);
-		if (argv[0])
+		if (argv[0]) {
+			idx = 0;
+			while (env[idx])
+				putenv(env[idx++]);
 			spawn_and_wait(argv);
-		idx = 0;
-		while (env[idx])
-			bb_unsetenv(env[idx++]);
+			idx = 0;
+			while (env[idx])
+				bb_unsetenv(env[idx++]);
+		}
 		munmap(netbuf, BUFFER_SIZE);
 	}