[NETFILTER]: Fix HW checksum handling in TCPMSS target

Most importantly, remove bogus BUG() in receive path.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/ipv4/netfilter/ipt_TCPMSS.c b/net/ipv4/netfilter/ipt_TCPMSS.c
index 1049050b2bfb..7b84a254440e 100644
--- a/net/ipv4/netfilter/ipt_TCPMSS.c
+++ b/net/ipv4/netfilter/ipt_TCPMSS.c
@@ -61,6 +61,10 @@ ipt_tcpmss_target(struct sk_buff **pskb,
         if (!skb_ip_make_writable(pskb, (*pskb)->len))
                 return NF_DROP;
 
+        if ((*pskb)->ip_summed == CHECKSUM_HW &&
+            skb_checksum_help(*pskb, out == NULL))
+                return NF_DROP;
+
         iph = (*pskb)->nh.iph;
         tcplen = (*pskb)->len - iph->ihl*4;
 
@@ -186,9 +190,6 @@ ipt_tcpmss_target(struct sk_buff **pskb,
                newmss);
 
  retmodified:
-        /* We never hw checksum SYN packets.  */
-        BUG_ON((*pskb)->ip_summed == CHECKSUM_HW);
-
         (*pskb)->nfcache |= NFC_UNKNOWN | NFC_ALTERED;
         return IPT_CONTINUE;
 }