[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>

1 files changed, 9 insertions, 6 deletions

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index e238b17f554..02a899bec19 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -514,12 +514,15 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 
         saddr = iph->daddr;
         if (!(rt->rt_flags & RTCF_LOCAL)) {
-                /* This is broken, skb_in->dev points to the outgoing device
-                 * after the packet passes through ip_output().
-                 */
-                if (skb_in->dev && 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;
         }