From 434a34838034347f45fb9a47df55b1a36e5addfd Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Fri, 17 Jul 2020 21:31:24 +0900
Subject: [PATCH] netlink: do not fail when new interface name is already used
 as an alternative name

When renaming a network interface, the new name may be used as an
alternative name. In that case, let's swap the current name and the
alternative name. That is, first drop the new name from the list of
alternative names, then rename the interface, finally set the old name
as an alternative name.
---
 src/libsystemd/sd-netlink/netlink-util.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/libsystemd/sd-netlink/netlink-util.c b/src/libsystemd/sd-netlink/netlink-util.c
index 83f2a9b9264..a6ea5eb6d58 100644
--- a/src/libsystemd/sd-netlink/netlink-util.c
+++ b/src/libsystemd/sd-netlink/netlink-util.c
@@ -2,6 +2,7 @@
 
 #include "sd-netlink.h"
 
+#include "format-util.h"
 #include "memory-util.h"
 #include "netlink-internal.h"
 #include "netlink-util.h"
@@ -9,6 +10,8 @@
 
 int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
         _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *message = NULL;
+        _cleanup_strv_free_ char **alternative_names = NULL;
+        char old_name[IF_NAMESIZE + 1] = {};
         int r;
 
         assert(rtnl);
@@ -18,10 +21,18 @@ int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
         if (!ifname_valid(name))
                 return -EINVAL;
 
-        if (!*rtnl) {
-                r = sd_netlink_open(rtnl);
+        r = rtnl_get_link_alternative_names(rtnl, ifindex, &alternative_names);
+        if (r < 0)
+                log_debug_errno(r, "Failed to get alternative names on network interface %i, ignoring: %m",
+                                ifindex);
+
+        if (strv_contains(alternative_names, name)) {
+                r = rtnl_delete_link_alternative_names(rtnl, ifindex, STRV_MAKE(name));
                 if (r < 0)
-                        return r;
+                        return log_debug_errno(r, "Failed to remove '%s' from alternative names on network interface %i: %m",
+                                               name, ifindex);
+
+                format_ifname(ifindex, old_name);
         }
 
         r = sd_rtnl_message_new_link(*rtnl, &message, RTM_SETLINK, ifindex);
@@ -36,6 +47,13 @@ int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
         if (r < 0)
                 return r;
 
+        if (!isempty(old_name)) {
+                r = rtnl_set_link_alternative_names(rtnl, ifindex, STRV_MAKE(old_name));
+                if (r < 0)
+                        log_debug_errno(r, "Failed to set '%s' as an alternative name on network interface %i, ignoring: %m",
+                                        old_name, ifindex);
+        }
+
         return 0;
 }
 
-- 
2.47.3