fib_rules: return 0 directly if an exactly same rule exists when NLM_F_EXCL not supplied

With commit 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to
fib_nl_newrule") we now able to check if a rule already exists. But this
only works with iproute2. For other tools like libnl, NetworkManager,
it still could add duplicate rules with only NLM_F_CREATE flag, like

[localhost ~ ]# ip rule
0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup default
100000: from 192.168.7.5 lookup 5
100000: from 192.168.7.5 lookup 5

As it doesn't make sense to create two duplicate rules, let's just return
0 if the rule exists.

Fixes: 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to fib_nl_newrule")
Reported-by: Thomas Haller <thaller@redhat.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 18f8dd8..43f0115 100644 (file)
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -757,9 +757,9 @@ int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr *nlh,
        if (err)
                goto errout;
 
-       if ((nlh->nlmsg_flags & NLM_F_EXCL) &&
-           rule_exists(ops, frh, tb, rule)) {
-               err = -EEXIST;
+       if (rule_exists(ops, frh, tb, rule)) {
+               if (nlh->nlmsg_flags & NLM_F_EXCL)
+                       err = -EEXIST;
                goto errout_free;
        }