From 6df56a7905ad44949885c90d97f246a77309112e Mon Sep 17 00:00:00 2001
From: Michal Schmidt <mschmidt@redhat.com>
Date: Mon, 28 Jan 2013 14:15:56 +0100
Subject: [PATCH] (F18) Revert "udev: network device renaming - immediately
 give up if the target name isn't available"

This reverts commit 97595710b77aa162ca5e20da57d0a1ed7355eaad (and fixes
it up for printk_kmsg-related changes that came later).

Many users upgraded from earlier Fedora releases and kept their
/etc/udev/rules.d/70-persistent-net.rules with rules renaming interfaces
into the ethX namespace. The udev change that made this entirely
unsupported was not announced loud enough. For F18 let's re-add the
renaming hack.

Add an annoying message about the need to fix udev rules.

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=896135
---
 src/udev/udev-event.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/src/udev/udev-event.c b/src/udev/udev-event.c
index 3db2cb7..4253bbd 100644
--- a/src/udev/udev-event.c
+++ b/src/udev/udev-event.c
@@ -750,7 +750,14 @@ static int rename_netif(struct udev_event *event)
         struct udev_device *dev = event->dev;
         int sk;
         struct ifreq ifr;
+        int loop;
         int err;
+        static const char rename_hack_msg_fmt[] =
+                "Tried to rename network interface %s, but the target name %s already exists! "
+                "The names that udev rules assign to network interfaces must be changed. "
+                "Avoid names that collide with kernel created ones. "
+                "A workaround will be attempted now, but this WILL BREAK in a future release! "
+                "See https://bugs.freedesktop.org/show_bug.cgi?id=56929#c3\n";
 
         log_debug("changing net interface name from '%s' to '%s'\n",
                   udev_device_get_sysname(dev), event->name);
@@ -766,12 +773,53 @@ static int rename_netif(struct udev_event *event)
         strscpy(ifr.ifr_name, IFNAMSIZ, udev_device_get_sysname(dev));
         strscpy(ifr.ifr_newname, IFNAMSIZ, event->name);
         err = ioctl(sk, SIOCSIFNAME, &ifr);
-        if (err >= 0) {
+        if (err == 0) {
                 print_kmsg("renamed network interface %s to %s\n", ifr.ifr_name, ifr.ifr_newname);
-        } else {
+                goto out;
+        }
+
+        /* keep trying if the destination interface name already exists */
+        err = -errno;
+        if (err != -EEXIST)
+                goto out;
+
+        /* F18: scream both into dmesg and journal */
+        print_kmsg(rename_hack_msg_fmt, ifr.ifr_name, ifr.ifr_newname);
+        log_error (rename_hack_msg_fmt, ifr.ifr_name, ifr.ifr_newname);
+
+        /* 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;
-                log_error("error changing net interface name %s to %s: %m\n", ifr.ifr_name, ifr.ifr_newname);
+                goto out;
+        }
+
+        /* log temporary name */
+        print_kmsg("renamed network interface %s to %s\n", ifr.ifr_name, ifr.ifr_newname);
+
+        /* wait a maximum of 90 seconds for our target to become available */
+        strscpy(ifr.ifr_name, IFNAMSIZ, ifr.ifr_newname);
+        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) {
+                        print_kmsg("renamed network interface %s to %s\n", ifr.ifr_name, ifr.ifr_newname);
+                        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);
         close(sk);
         return err;
 }