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);
         }