net: plumb extack in __dev_change_net_namespace()

It could be hard to understand why the netlink command fails. For example,
if dev->netns_immutable is set, the error is "Invalid argument".

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b8728d67ea91d99cc0fc3836e0d8f02ad4f3674f..7ab86ec228b7fb25e64c295aca6da28dfeff8dec 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4191,12 +4191,13 @@ int dev_change_flags(struct net_device *dev, unsigned int flags,
 int dev_set_alias(struct net_device *, const char *, size_t);
 int dev_get_alias(const struct net_device *, char *, size_t);
 int __dev_change_net_namespace(struct net_device *dev, struct net *net,
-                              const char *pat, int new_ifindex);
+                              const char *pat, int new_ifindex,
+                              struct netlink_ext_ack *extack);
 static inline
 int dev_change_net_namespace(struct net_device *dev, struct net *net,
                             const char *pat)
 {
-       return __dev_change_net_namespace(dev, net, pat, 0);
+       return __dev_change_net_namespace(dev, net, pat, 0, NULL);
 }
 int __dev_set_mtu(struct net_device *, int);
 int dev_set_mtu(struct net_device *, int);

diff --git a/net/core/dev.c b/net/core/dev.c
index 357ae88064a5fa25489427d9298f7925659742e1..5c9d2bd29e156ab7f4f54fe09afc2a7082af2082 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -12131,6 +12131,7 @@ EXPORT_SYMBOL(unregister_netdev);
  *           is already taken in the destination network namespace.
  *     @new_ifindex: If not zero, specifies device index in the target
  *                   namespace.
+ *     @extack: netlink extended ack
  *
  *     This function shuts down a device interface and moves it
  *     to a new network namespace. On success 0 is returned, on
@@ -12140,7 +12141,8 @@ EXPORT_SYMBOL(unregister_netdev);
  */
 
 int __dev_change_net_namespace(struct net_device *dev, struct net *net,
-                              const char *pat, int new_ifindex)
+                              const char *pat, int new_ifindex,
+                              struct netlink_ext_ack *extack)
 {
        struct netdev_name_node *name_node;
        struct net *net_old = dev_net(dev);
@@ -12151,12 +12153,16 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 
        /* Don't allow namespace local devices to be moved. */
        err = -EINVAL;
-       if (dev->netns_immutable)
+       if (dev->netns_immutable) {
+               NL_SET_ERR_MSG(extack, "The interface netns is immutable");
                goto out;
+       }
 
        /* Ensure the device has been registered */
-       if (dev->reg_state != NETREG_REGISTERED)
+       if (dev->reg_state != NETREG_REGISTERED) {
+               NL_SET_ERR_MSG(extack, "The interface isn't registered");
                goto out;
+       }
 
        /* Get out if there is nothing todo */
        err = 0;
@@ -12169,30 +12175,49 @@ int __dev_change_net_namespace(struct net_device *dev, struct net *net,
        err = -EEXIST;
        if (netdev_name_in_use(net, dev->name)) {
                /* We get here if we can't use the current device name */
-               if (!pat)
+               if (!pat) {
+                       NL_SET_ERR_MSG(extack,
+                                      "An interface with the same name exists in the target netns");
                        goto out;
+               }
                err = dev_prep_valid_name(net, dev, pat, new_name, EEXIST);
-               if (err < 0)
+               if (err < 0) {
+                       NL_SET_ERR_MSG_FMT(extack,
+                                          "Unable to use '%s' for the new interface name in the target netns",
+                                          pat);
                        goto out;
+               }
        }
        /* Check that none of the altnames conflicts. */
        err = -EEXIST;
-       netdev_for_each_altname(dev, name_node)
-               if (netdev_name_in_use(net, name_node->name))
+       netdev_for_each_altname(dev, name_node) {
+               if (netdev_name_in_use(net, name_node->name)) {
+                       NL_SET_ERR_MSG_FMT(extack,
+                                          "An interface with the altname %s exists in the target netns",
+                                          name_node->name);
                        goto out;
+               }
+       }
 
        /* Check that new_ifindex isn't used yet. */
        if (new_ifindex) {
                err = dev_index_reserve(net, new_ifindex);
-               if (err < 0)
+               if (err < 0) {
+                       NL_SET_ERR_MSG_FMT(extack,
+                                          "The ifindex %d is not available in the target netns",
+                                          new_ifindex);
                        goto out;
+               }
        } else {
                /* If there is an ifindex conflict assign a new one */
                err = dev_index_reserve(net, dev->ifindex);
                if (err == -EBUSY)
                        err = dev_index_reserve(net, 0);
-               if (err < 0)
+               if (err < 0) {
+                       NL_SET_ERR_MSG(extack,
+                                      "Unable to allocate a new ifindex in the target netns");
                        goto out;
+               }
                new_ifindex = err;
        }
 

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 8b6bf5e9bb3422df0b025507e396730f27a182b2..b4612d305970465e1ec26271d6b06cd2e0ff88a2 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3028,7 +3028,7 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
 
                new_ifindex = nla_get_s32_default(tb[IFLA_NEW_IFINDEX], 0);
 
-               err = __dev_change_net_namespace(dev, tgt_net, pat, new_ifindex);
+               err = __dev_change_net_namespace(dev, tgt_net, pat, new_ifindex, extack);
                if (err)
                        goto errout;