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From 6db267672de69d6bf4809f433cde106e11145ca8 Mon Sep 17 00:00:00 2001
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From: Yu Watanabe <watanabe.yu+github@gmail.com>
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Date: Fri, 17 Jul 2020 21:31:24 +0900
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Subject: [PATCH] netlink: do not fail when new interface name is already used
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 as an alternative name
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When renaming a network interface, the new name may be used as an
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alternative name. In that case, let's swap the current name and the
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alternative name. That is, first drop the new name from the list of
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alternative names, then rename the interface, finally set the old name
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as an alternative name.
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(cherry picked from commit 434a34838034347f45fb9a47df55b1a36e5addfd)
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Related: #1850986
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---
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 src/libsystemd/sd-netlink/netlink-util.c | 30 +++++++++++++++++++++---
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 1 file changed, 27 insertions(+), 3 deletions(-)
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diff --git a/src/libsystemd/sd-netlink/netlink-util.c b/src/libsystemd/sd-netlink/netlink-util.c
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index 7f09261981..4e42ef9e26 100644
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--- a/src/libsystemd/sd-netlink/netlink-util.c
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+++ b/src/libsystemd/sd-netlink/netlink-util.c
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@@ -1,23 +1,40 @@
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 /* SPDX-License-Identifier: LGPL-2.1+ */
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+#include <net/if.h>
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+
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 #include "sd-netlink.h"
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 #include "netlink-internal.h"
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 #include "netlink-util.h"
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+#include "socket-util.h"
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+#include "string-util.h"
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 #include "strv.h"
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 int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
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         _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *message = NULL;
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+        _cleanup_strv_free_ char **alternative_names = NULL;
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+        char old_name[IF_NAMESIZE + 1] = {};
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         int r;
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         assert(rtnl);
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         assert(ifindex > 0);
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         assert(name);
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-        if (!*rtnl) {
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-                r = sd_netlink_open(rtnl);
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+        if (!ifname_valid(name))
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+                return -EINVAL;
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+
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+        r = rtnl_get_link_alternative_names(rtnl, ifindex, &alternative_names);
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+        if (r < 0)
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+                log_debug_errno(r, "Failed to get alternative names on network interface %i, ignoring: %m",
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+                                ifindex);
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+
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+        if (strv_contains(alternative_names, name)) {
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+                r = rtnl_delete_link_alternative_names(rtnl, ifindex, STRV_MAKE(name));
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                 if (r < 0)
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-                        return r;
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+                        return log_debug_errno(r, "Failed to remove '%s' from alternative names on network interface %i: %m",
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+                                               name, ifindex);
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+
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+                if_indextoname(ifindex, old_name);
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         }
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         r = sd_rtnl_message_new_link(*rtnl, &message, RTM_SETLINK, ifindex);
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@@ -32,6 +49,13 @@ int rtnl_set_link_name(sd_netlink **rtnl, int ifindex, const char *name) {
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         if (r < 0)
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                 return r;
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+        if (!isempty(old_name)) {
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+                r = rtnl_set_link_alternative_names(rtnl, ifindex, STRV_MAKE(old_name));
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+                if (r < 0)
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+                        log_debug_errno(r, "Failed to set '%s' as an alternative name on network interface %i, ignoring: %m",
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+                                        old_name, ifindex);
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+        }
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+
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         return 0;
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 }
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