[PATCH] ICMP: Fix icmp_errors_use_inbound_ifaddr sysctl

Currently when icmp_errors_use_inbound_ifaddr is set and an ICMP error is
sent after the packet passed through ip_output(), an address from the
outgoing interface is chosen as ICMP source address since skb->dev doesn't
point to the incoming interface anymore.

Fix this by doing an interface lookup on rt->dst.iif and using that device.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

net/ipv4/icmp.c

@@ -513,9 +513,15 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 
 	saddr = iph->daddr;
 	if (!(rt->rt_flags & RTCF_LOCAL)) {
-		if (sysctl_icmp_errors_use_inbound_ifaddr)
-			saddr = inet_select_addr(skb_in->dev, 0, RT_SCOPE_LINK);
-		else
+		struct net_device *dev = NULL;
+
+		if (rt->fl.iif && sysctl_icmp_errors_use_inbound_ifaddr)
+			dev = dev_get_by_index(rt->fl.iif);
+
+		if (dev) {
+			saddr = inet_select_addr(dev, 0, RT_SCOPE_LINK);
+			dev_put(dev);
+		} else
 			saddr = 0;
 	}