netdev - Re: [PATCH] ipv4: remove all rt cache entries on UNREGISTER event

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Date:	Wed, 29 Sep 2010 11:18:49 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	nicolas.dichtel@...nd.com
Cc:	netdev <netdev@...r.kernel.org>,
	Octavian Purdila <opurdila@...acom.com>
Subject: Re: [PATCH] ipv4: remove all rt cache entries on UNREGISTER event

I found following patch was enough to avoid route being created if
device is down. This is still racy and needs more thinking.


diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index ac6559c..1ee0b1a 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2586,9 +2586,10 @@ static int ip_route_output_slow(struct net *net, struct rtable **rp,
 			goto out;
 
 		/* RACE: Check return value of inet_select_addr instead. */
-		if (__in_dev_get_rtnl(dev_out) == NULL) {
+		if (!(dev_out->flags & IFF_UP) || __in_dev_get_rtnl(dev_out) == NULL) {
 			dev_put(dev_out);
-			goto out;	/* Wrong error code */
+			err = -ENETUNREACH;
+			goto out;
 		}
 
 		if (ipv4_is_local_multicast(oldflp->fl4_dst) ||


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