ipv4: fix sending of redirects

After "Cache input routes in fib_info nexthops" (commit
d2d68ba9fe) and "Elide fib_validate_source() completely when possible"
(commit 7a9bc9b81a) we can not send ICMP redirects. It seems we
should not cache the RTCF_DOREDIRECT flag in nh_rth_input because
the same fib_info can be used for traffic that is not redirected,
eg. from other input devices or from sources that are not in same subnet.

	As result, we have to disable the caching of RTCF_DOREDIRECT
flag and to force source validation for the case when forwarding
traffic to the input device. If traffic comes from directly connected
source we allow redirection as it was done before both changes.

	Avoid setting RTCF_DOREDIRECT if IN_DEV_TX_REDIRECTS
is disabled, this can avoid source address validation and to
help caching the routes.

	After the change "Adjust semantics of rt->rt_gateway"
(commit f8126f1d51) we should make sure our ICMP_REDIR_HOST messages
contain daddr instead of 0.0.0.0 when target is directly connected.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 68c93d1bb03adb9fef46ff264a783dad82a962ea..825c608826de1c4b5dea08c46e6ff4255117c990 100644 (file)
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -322,7 +322,8 @@ int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
 {
        int r = secpath_exists(skb) ? 0 : IN_DEV_RPFILTER(idev);
 
-       if (!r && !fib_num_tclassid_users(dev_net(dev))) {
+       if (!r && !fib_num_tclassid_users(dev_net(dev)) &&
+           (dev->ifindex != oif || !IN_DEV_TX_REDIRECTS(idev))) {
                *itag = 0;
                return 0;
        }

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 132e0dfee53a10f1558e3fb49266c43bd3c2a75c..b90da1bc27043b43108de4e1be23a1d75ddf5381 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -802,7 +802,8 @@ void ip_rt_send_redirect(struct sk_buff *skb)
        net = dev_net(rt->dst.dev);
        peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr, 1);
        if (!peer) {
-               icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, rt->rt_gateway);
+               icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST,
+                         rt_nexthop(rt, ip_hdr(skb)->daddr));
                return;
        }
 
@@ -827,7 +828,9 @@ void ip_rt_send_redirect(struct sk_buff *skb)
            time_after(jiffies,
                       (peer->rate_last +
                        (ip_rt_redirect_load << peer->rate_tokens)))) {
-               icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, rt->rt_gateway);
+               __be32 gw = rt_nexthop(rt, ip_hdr(skb)->daddr);
+
+               icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, gw);
                peer->rate_last = jiffies;
                ++peer->rate_tokens;
 #ifdef CONFIG_IP_ROUTE_VERBOSE
@@ -835,7 +838,7 @@ void ip_rt_send_redirect(struct sk_buff *skb)
                    peer->rate_tokens == ip_rt_redirect_number)
                        net_warn_ratelimited("host %pI4/if%d ignores redirects for %pI4 to %pI4\n",
                                             &ip_hdr(skb)->saddr, inet_iif(skb),
-                                            &ip_hdr(skb)->daddr, &rt->rt_gateway);
+                                            &ip_hdr(skb)->daddr, &gw);
 #endif
        }
 out_put_peer:
@@ -1442,10 +1445,13 @@ static int __mkroute_input(struct sk_buff *skb,
                goto cleanup;
        }
 
-       if (out_dev == in_dev && err &&
+       do_cache = res->fi && !itag;
+       if (out_dev == in_dev && err && IN_DEV_TX_REDIRECTS(out_dev) &&
            (IN_DEV_SHARED_MEDIA(out_dev) ||
-            inet_addr_onlink(out_dev, saddr, FIB_RES_GW(*res))))
+            inet_addr_onlink(out_dev, saddr, FIB_RES_GW(*res)))) {
                flags |= RTCF_DOREDIRECT;
+               do_cache = false;
+       }
 
        if (skb->protocol != htons(ETH_P_IP)) {
                /* Not IP (i.e. ARP). Do not create route, if it is
@@ -1462,15 +1468,11 @@ static int __mkroute_input(struct sk_buff *skb,
                }
        }
 
-       do_cache = false;
-       if (res->fi) {
-               if (!itag) {
-                       rth = rcu_dereference(FIB_RES_NH(*res).nh_rth_input);
-                       if (rt_cache_valid(rth)) {
-                               skb_dst_set_noref(skb, &rth->dst);
-                               goto out;
-                       }
-                       do_cache = true;
+       if (do_cache) {
+               rth = rcu_dereference(FIB_RES_NH(*res).nh_rth_input);
+               if (rt_cache_valid(rth)) {
+                       skb_dst_set_noref(skb, &rth->dst);
+                       goto out;
                }
        }