net: Discard and warn about LRO'd skbs received for forwarding

Add skb_warn_if_lro() to test whether an skb was received with LRO and
warn if so.

Change br_forward(), ip_forward() and ip6_forward() to call it) and
discard the skb if it returns true.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 15 insertions, 1 deletions

diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index 512645727f51..bdd9ccea17ce 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -89,7 +89,7 @@ void br_deliver(const struct net_bridge_port *to, struct sk_buff *skb)
 /* called with rcu_read_lock */
 void br_forward(const struct net_bridge_port *to, struct sk_buff *skb)
 {
-        if (should_deliver(to, skb)) {
+        if (!skb_warn_if_lro(skb) && should_deliver(to, skb)) {
                 __br_forward(to, skb);
                 return;
         }
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3e18f8525e82..2df012be973d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2583,6 +2583,13 @@ bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off)
         return true;
 }
 
+void __skb_warn_lro_forwarding(const struct sk_buff *skb)
+{
+        if (net_ratelimit())
+                pr_warning("%s: received packets cannot be forwarded"
+                           " while LRO is enabled\n", skb->dev->name);
+}
+
 EXPORT_SYMBOL(___pskb_trim);
 EXPORT_SYMBOL(__kfree_skb);
 EXPORT_SYMBOL(kfree_skb);
@@ -2616,6 +2623,7 @@ EXPORT_SYMBOL(skb_seq_read);
 EXPORT_SYMBOL(skb_abort_seq_read);
 EXPORT_SYMBOL(skb_find_text);
 EXPORT_SYMBOL(skb_append_datato_frags);
+EXPORT_SYMBOL(__skb_warn_lro_forwarding);
 
 EXPORT_SYMBOL_GPL(skb_to_sgvec);
 EXPORT_SYMBOL_GPL(skb_cow_data);
diff --git a/net/ipv4/ip_forward.c b/net/ipv4/ip_forward.c
index 37d36a3f33cd..da14725916d3 100644
--- a/net/ipv4/ip_forward.c
+++ b/net/ipv4/ip_forward.c
@@ -56,6 +56,9 @@ int ip_forward(struct sk_buff *skb)
         struct rtable *rt;      /* Route we use */
         struct ip_options * opt = &(IPCB(skb)->opt);
 
+        if (skb_warn_if_lro(skb))
+                goto drop;
+
         if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
                 goto drop;
 
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 40a2813a63d1..fd7cd1bfe151 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -407,6 +407,9 @@ int ip6_forward(struct sk_buff *skb)
         if (ipv6_devconf.forwarding == 0)
                 goto error;
 
+        if (skb_warn_if_lro(skb))
+                goto drop;
+
         if (!xfrm6_policy_check(NULL, XFRM_POLICY_FWD, skb)) {
                 IP6_INC_STATS(ip6_dst_idev(dst), IPSTATS_MIB_INDISCARDS);
                 goto drop;