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netfilter: xt_TCPMSS: handle CHECKSUM_COMPLETE in tcpmss_tg6() 

In case MSS option is added in TCP options, skb length increases by 4.
IPv6 needs to update skb->csum if skb has CHECKSUM_COMPLETE,
otherwise kernel complains loudly in netdev_rx_csum_fault() with a
stack dump.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Eric Dumazet 2016-01-15 08:21:32 -08:00 committed by Pablo Neira Ayuso
parent efaea94aaf
commit d6b3347bf1
1 changed files with 7 additions and 2 deletions
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9
net/netfilter/xt_TCPMSS.c
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@ -228,7 +228,7 @@ tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par)
{
struct ipv6hdr *ipv6h = ipv6_hdr(skb);
u8 nexthdr;
__be16 frag_off;
__be16 frag_off, oldlen, newlen;
int tcphoff;
int ret;
@ -244,7 +244,12 @@ tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par)
return NF_DROP;
if (ret > 0) {
ipv6h = ipv6_hdr(skb);
ipv6h->payload_len = htons(ntohs(ipv6h->payload_len) + ret);
oldlen = ipv6h->payload_len;
newlen = htons(ntohs(oldlen) + ret);
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_add(csum_sub(skb->csum, oldlen),
newlen);
ipv6h->payload_len = newlen;
}
return XT_CONTINUE;
}