inet: switch inet_dump_fib() to RCU protection

No longer hold RTNL while calling inet_dump_fib().

Also change return value for a completed dump:

Returning 0 instead of skb->len allows NLMSG_DONE
to be appended to the skb. User space does not have
to call us again to get a standalone NLMSG_DONE marker.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 39f67990e01c19b73a622dced0220a1bba21d5e6..bf3a2214fe29b6f9b494581b293259e6c5ce6f8c 100644 (file)
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -990,7 +990,7 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
        struct fib_dump_filter filter = {
                .dump_routes = true,
                .dump_exceptions = true,
-               .rtnl_held = true,
+               .rtnl_held = false,
        };
        const struct nlmsghdr *nlh = cb->nlh;
        struct net *net = sock_net(skb->sk);
@@ -998,12 +998,13 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
        unsigned int e = 0, s_e;
        struct fib_table *tb;
        struct hlist_head *head;
-       int dumped = 0, err;
+       int dumped = 0, err = 0;
 
+       rcu_read_lock();
        if (cb->strict_check) {
                err = ip_valid_fib_dump_req(net, nlh, &filter, cb);
                if (err < 0)
-                       return err;
+                       goto unlock;
        } else if (nlmsg_len(nlh) >= sizeof(struct rtmsg)) {
                struct rtmsg *rtm = nlmsg_data(nlh);
 
@@ -1012,29 +1013,28 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 
        /* ipv4 does not use prefix flag */
        if (filter.flags & RTM_F_PREFIX)
-               return skb->len;
+               goto unlock;
 
        if (filter.table_id) {
                tb = fib_get_table(net, filter.table_id);
                if (!tb) {
                        if (rtnl_msg_family(cb->nlh) != PF_INET)
-                               return skb->len;
+                               goto unlock;
 
                        NL_SET_ERR_MSG(cb->extack, "ipv4: FIB table does not exist");
-                       return -ENOENT;
+                       err = -ENOENT;
+                       goto unlock;
                }
-
-               rcu_read_lock();
                err = fib_table_dump(tb, skb, cb, &filter);
-               rcu_read_unlock();
-               return skb->len ? : err;
+               if (err < 0 && skb->len)
+                       err = skb->len;
+               goto unlock;
        }
 
        s_h = cb->args[0];
        s_e = cb->args[1];
 
-       rcu_read_lock();
-
+       err = 0;
        for (h = s_h; h < FIB_TABLE_HASHSZ; h++, s_e = 0) {
                e = 0;
                head = &net->ipv4.fib_table_hash[h];
@@ -1047,9 +1047,8 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
                        err = fib_table_dump(tb, skb, cb, &filter);
                        if (err < 0) {
                                if (likely(skb->len))
-                                       goto out;
-
-                               goto out_err;
+                                       err = skb->len;
+                               goto out;
                        }
                        dumped = 1;
 next:
@@ -1057,13 +1056,12 @@ next:
                }
        }
 out:
-       err = skb->len;
-out_err:
-       rcu_read_unlock();
 
        cb->args[1] = e;
        cb->args[0] = h;
 
+unlock:
+       rcu_read_unlock();
        return err;
 }
 
@@ -1666,5 +1664,6 @@ void __init ip_fib_init(void)
 
        rtnl_register(PF_INET, RTM_NEWROUTE, inet_rtm_newroute, NULL, 0);
        rtnl_register(PF_INET, RTM_DELROUTE, inet_rtm_delroute, NULL, 0);
-       rtnl_register(PF_INET, RTM_GETROUTE, NULL, inet_dump_fib, 0);
+       rtnl_register(PF_INET, RTM_GETROUTE, NULL, inet_dump_fib,
+                     RTNL_FLAG_DUMP_UNLOCKED);
 }

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 0fc7ab5832d1ae00e33fdf6fad4ef379c7d0bd4d..f474106464d2f2a52fa6b7ecaf2146977d05eecc 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -2368,7 +2368,7 @@ int fib_table_dump(struct fib_table *tb, struct sk_buff *skb,
         * and key == 0 means the dump has wrapped around and we are done.
         */
        if (count && !key)
-               return skb->len;
+               return 0;
 
        while ((l = leaf_walk_rcu(&tp, key)) != NULL) {
                int err;
@@ -2394,7 +2394,7 @@ int fib_table_dump(struct fib_table *tb, struct sk_buff *skb,
        cb->args[3] = key;
        cb->args[2] = count;
 
-       return skb->len;
+       return 0;
 }
 
 void __init fib_trie_init(void)