src/udev/udev-event.c: restore code to allow rule generator to work

This code was dropped while importing from upstream.  It is needed
to allow the legacy renaming of interfaces like eth* or wlan*.

X-Eudev-Bug: 56
X-Eudev-Bug-URL: #56
Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

configure.ac

@@ -303,6 +303,10 @@ AC_ARG_ENABLE([rule-generator],
         AS_HELP_STRING([--enable-rule-generator], [enable legacy persistent network, cdrom support]),
         [], [enable_rule_generator=no])
 
+if test "x${enable_rule_generator}" != xno; then
+        AC_DEFINE([ENABLE_RULE_GENERATOR], [1], [Define if we are enabling rule generator])
+fi
+
 AM_CONDITIONAL([ENABLE_RULE_GENERATOR], [test "x$enable_rule_generator" = xyes])
 
 # ------------------------------------------------------------------------------

src/udev/udev-event.c

@@ -752,6 +752,28 @@ int udev_event_spawn(struct udev_event *event,
         return err;
 }
 
+#ifdef ENABLE_RULE_GENERATOR
+static void rename_netif_kernel_log(struct ifreq ifr)
+{
+        int klog;
+        FILE *f;
+
+        klog = open("/dev/kmsg", O_WRONLY|O_CLOEXEC);
+        if (klog < 0)
+                return;
+
+        f = fdopen(klog, "w");
+        if (f == NULL) {
+                close(klog);
+                return;
+        }
+
+        fprintf(f, "<30>udevd[%u]: renamed network interface %s to %s\n",
+                getpid(), ifr.ifr_name, ifr.ifr_newname);
+        fclose(f);
+}
+#endif
+
 static int rename_netif(struct udev_event *event)
 {
         struct udev_device *dev = event->dev;
@@ -773,12 +795,62 @@ static int rename_netif(struct udev_event *event)
         util_strscpy(ifr.ifr_name, IFNAMSIZ, udev_device_get_sysname(dev));
         util_strscpy(ifr.ifr_newname, IFNAMSIZ, event->name);
         err = ioctl(sk, SIOCSIFNAME, &ifr);
+
+#ifdef ENABLE_RULE_GENERATOR
+        int loop;
+
+        if (err == 0) {
+                rename_netif_kernel_log(ifr);
+                goto out;
+        }
+
+        /* keep trying if the destination interface name already exists */
+        err = -errno;
+        if (err != -EEXIST)
+                goto out;
+
+        /* free our own name, another process may wait for us */
+        snprintf(ifr.ifr_newname, IFNAMSIZ, "rename%u", udev_device_get_ifindex(dev));
+        err = ioctl(sk, SIOCSIFNAME, &ifr);
+        if (err < 0) {
+                err = -errno;
+                goto out;
+        }
+
+        /* log temporary name */
+        rename_netif_kernel_log(ifr);
+
+        /* wait a maximum of 90 seconds for our target to become available */
+        util_strscpy(ifr.ifr_name, IFNAMSIZ, ifr.ifr_newname);
+        util_strscpy(ifr.ifr_newname, IFNAMSIZ, event->name);
+        loop = 90 * 20;
+        while (loop--) {
+                const struct timespec duration = { 0, 1000 * 1000 * 1000 / 20 };
+
+                nanosleep(&duration, NULL);
+
+                err = ioctl(sk, SIOCSIFNAME, &ifr);
+                if (err == 0) {
+                        rename_netif_kernel_log(ifr);
+                        break;
+                }
+                err = -errno;
+                if (err != -EEXIST)
+                        break;
+        }
+
+out:
+        if (err < 0)
+                log_error("error changing net interface name %s to %s: %m\n", ifr.ifr_name, ifr.ifr_newname);
+#else
         if (err >= 0) {
                 print_kmsg("renamed network interface %s to %s\n", ifr.ifr_name, ifr.ifr_newname);
         } else {
                 err = -errno;
                 log_error("error changing net interface name %s to %s: %m\n", ifr.ifr_name, ifr.ifr_newname);
         }
+#endif
+
         close(sk);
         return err;
 }