[PATCH v2] fib_rules: Added NLM_F_EXCL support to fib_nl_newrule

When adding rule with NLM_F_EXCL flag then check if the same rule exist.
If yes then exit with -EEXIST.

This is already implemented in iproute2:
	if (cmd == RTM_NEWRULE) {
		req.n.nlmsg_flags |= NLM_F_CREATE|NLM_F_EXCL;
		req.r.rtm_type = RTN_UNICAST;
	}

Tested ipv4 and ipv6 with net-next linux on qemu x86

expected behavior after patch:
localhost ~ # ip rule
0:    from all lookup local
32766:    from all lookup main
32767:    from all lookup default
localhost ~ # ip rule add from 10.46.177.97 lookup 104 pref 1005
localhost ~ # ip rule add from 10.46.177.97 lookup 104 pref 1005
RTNETLINK answers: File exists
localhost ~ # ip rule
0:    from all lookup local
1005:    from 10.46.177.97 lookup 104
32766:    from all lookup main
32767:    from all lookup default

There was already topic regarding this but I don't see any changes
merged and problem still occurs.
https://lkml.kernel.org/r/1135778809.5944.7.camel+%28%29+localhost+%21+localdomain

Signed-off-by: Mateusz Bajorski <redacted>
---
Changes in v2: section moved to new place where new rule is already built

 net/core/fib_rules.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 840aceb..5bc1d27 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c

@@ -371,6 +371,40 @@ static int fib_nl_newrule(struct sk_buff *skb, struct nlmsghdr* nlh)
 	} else if (rule->action == FR_ACT_GOTO)
 		goto errout_free;
 
+	if (nlh->nlmsg_flags & NLM_F_EXCL) {
+		list_for_each_entry(r, &ops->rules_list, list) {
+			if (r->action != rule->action)
+				continue;
+
+			if (r->table != rule->table)
+				continue;
+
+			if (r->pref != rule->pref)
+				continue;
+
+			if (memcmp(r->iifname, rule->iifname, IFNAMSIZ))
+				continue;
+
+			if (memcmp(r->oifname, rule->oifname, IFNAMSIZ))
+				continue;
+
+			if (r->mark != rule->mark)
+				continue;
+
+			if (r->mark_mask != rule->mark_mask)
+				continue;
+
+			if (r->tun_id != rule->tun_id)
+				continue;
+
+			if (!ops->compare(r, frh, tb))
+				continue;
+
+			err = -EEXIST;
+			goto errout_free;
+		}
+	}
+
 	err = ops->configure(rule, skb, frh, tb);
 	if (err < 0)
 		goto errout_free;

-- 
2.6.4