From d6b3347bf178266259af64b1f27b5cf54acf62c8 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 15 Jan 2016 08:21:32 -0800 Subject: [PATCH] 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 Signed-off-by: Pablo Neira Ayuso --- net/netfilter/xt_TCPMSS.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c index b7c43def0dc6..e118397254af 100644 --- a/net/netfilter/xt_TCPMSS.c +++ b/net/netfilter/xt_TCPMSS.c @@ -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; } -- 2.20.1