rtnetlink: Register rtnl_dellink() and rtnl_setlink() with RTNL_FLAG_DOIT_PERNET_WIP.

Currently, rtnl_setlink() and rtnl_dellink() cannot be fully converted
to per-netns RTNL due to a lack of handling peer/lower/upper devices in
different netns.

For example, when we change a device in rtnl_setlink() and need to
propagate that to its upper devices, we want to avoid acquiring all netns
locks, for which we do not know the upper limit.

The same situation happens when we remove a device.

rtnl_dellink() could be transformed to remove a single device in the
requested netns and delegate other devices to per-netns work, and
rtnl_setlink() might be ?

Until we come up with a better idea, let's use a new flag
RTNL_FLAG_DOIT_PERNET_WIP for rtnl_dellink() and rtnl_setlink().

This will unblock converting RTNL users where such devices are not related.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241108004823.29419-11-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index bef76abcff8d8986c9d268461dd735f603114e2e..bc0069a8b6ea12263a34b333ef2946c9db036059 100644 (file)
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -13,6 +13,7 @@ typedef int (*rtnl_dumpit_func)(struct sk_buff *, struct netlink_callback *);
 enum rtnl_link_flags {
        RTNL_FLAG_DOIT_UNLOCKED         = BIT(0),
 #define RTNL_FLAG_DOIT_PERNET          RTNL_FLAG_DOIT_UNLOCKED
+#define RTNL_FLAG_DOIT_PERNET_WIP      RTNL_FLAG_DOIT_UNLOCKED
        RTNL_FLAG_BULK_DEL_SUPPORTED    = BIT(1),
        RTNL_FLAG_DUMP_UNLOCKED         = BIT(2),
        RTNL_FLAG_DUMP_SPLIT_NLM_DONE   = BIT(3),       /* legacy behavior */

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 30191d17add3171bb3087649f44ae44a3c94b33e..327fa4957929d578cee8129a77dfa0bd8c6d9594 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3379,6 +3379,7 @@ static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh,
        struct net *net = sock_net(skb->sk);
        struct nlattr *tb[IFLA_MAX+1];
        struct net_device *dev = NULL;
+       struct rtnl_nets rtnl_nets;
        struct net *tgt_net;
        int err;
 
@@ -3397,6 +3398,12 @@ static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh,
                goto errout;
        }
 
+       rtnl_nets_init(&rtnl_nets);
+       rtnl_nets_add(&rtnl_nets, get_net(net));
+       rtnl_nets_add(&rtnl_nets, tgt_net);
+
+       rtnl_nets_lock(&rtnl_nets);
+
        if (ifm->ifi_index > 0)
                dev = __dev_get_by_index(net, ifm->ifi_index);
        else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME])
@@ -3409,7 +3416,7 @@ static int rtnl_setlink(struct sk_buff *skb, struct nlmsghdr *nlh,
        else if (!err)
                err = -ENODEV;
 
-       put_net(tgt_net);
+       rtnl_nets_unlock(&rtnl_nets);
 errout:
        return err;
 }
@@ -3494,6 +3501,8 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
                        return PTR_ERR(tgt_net);
        }
 
+       rtnl_net_lock(tgt_net);
+
        if (ifm->ifi_index > 0)
                dev = __dev_get_by_index(tgt_net, ifm->ifi_index);
        else if (tb[IFLA_IFNAME] || tb[IFLA_ALT_IFNAME])
@@ -3508,6 +3517,8 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
        else
                err = -EINVAL;
 
+       rtnl_net_unlock(tgt_net);
+
        if (netnsid >= 0)
                put_net(tgt_net);
 
@@ -6994,10 +7005,12 @@ static struct pernet_operations rtnetlink_net_ops = {
 static const struct rtnl_msg_handler rtnetlink_rtnl_msg_handlers[] __initconst = {
        {.msgtype = RTM_NEWLINK, .doit = rtnl_newlink,
         .flags = RTNL_FLAG_DOIT_PERNET},
-       {.msgtype = RTM_DELLINK, .doit = rtnl_dellink},
+       {.msgtype = RTM_DELLINK, .doit = rtnl_dellink,
+        .flags = RTNL_FLAG_DOIT_PERNET_WIP},
        {.msgtype = RTM_GETLINK, .doit = rtnl_getlink,
         .dumpit = rtnl_dump_ifinfo, .flags = RTNL_FLAG_DUMP_SPLIT_NLM_DONE},
-       {.msgtype = RTM_SETLINK, .doit = rtnl_setlink},
+       {.msgtype = RTM_SETLINK, .doit = rtnl_setlink,
+        .flags = RTNL_FLAG_DOIT_PERNET_WIP},
        {.msgtype = RTM_GETADDR, .dumpit = rtnl_dump_all},
        {.msgtype = RTM_GETROUTE, .dumpit = rtnl_dump_all},
        {.msgtype = RTM_GETNETCONF, .dumpit = rtnl_dump_all},