Don't verify checksum for outgoing packets because checksum calculation
may be done by the device.
Without this patch:
$ ip6tables -I OUTPUT -p tcp --dport 80 -j REJECT --reject-with tcp-reset
$ time telnet ipv6.google.com 80
Trying 2a00:1450:4010:c03::67...
telnet: Unable to connect to remote host: Connection timed out
real 0m7.201s
user 0m0.000s
sys 0m0.000s
With the patch applied:
$ ip6tables -I OUTPUT -p tcp --dport 80 -j REJECT --reject-with tcp-reset
$ time telnet ipv6.google.com 80
Trying 2a00:1450:4010:c03::67...
telnet: Unable to connect to remote host: Connection refused
real 0m0.085s
user 0m0.000s
sys 0m0.000s
Signed-off-by: Stanislav Fomichev <stfomichev@xxxxxxxxxxxxxx>
---
net/ipv6/netfilter/ip6t_REJECT.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/net/ipv6/netfilter/ip6t_REJECT.c b/net/ipv6/netfilter/ip6t_REJECT.c
index 56eef30ee5f6..3ef2b834bca3 100644
--- a/net/ipv6/netfilter/ip6t_REJECT.c
+++ b/net/ipv6/netfilter/ip6t_REJECT.c
@@ -39,7 +39,7 @@ MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv6");
MODULE_LICENSE("GPL");
/* Send RST reply */
-static void send_reset(struct net *net, struct sk_buff *oldskb)
+static void send_reset(struct net *net, struct sk_buff *oldskb, int hook)
{
struct sk_buff *nskb;
struct tcphdr otcph, *tcph;
@@ -88,8 +88,10 @@ static void send_reset(struct net *net, struct sk_buff *oldskb)
}
/* Check checksum. */
- if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP,
+ if (hook != NF_INET_LOCAL_OUT &&
+ csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP,
skb_checksum(oldskb, tcphoff, otcplen, 0))) {
+
pr_debug("TCP checksum is invalid\n");
return;
}
@@ -227,7 +229,7 @@ reject_tg6(struct sk_buff *skb, const struct xt_action_param *par)
/* Do nothing */
break;
case IP6T_TCP_RESET:
- send_reset(net, skb);
+ send_reset(net, skb, par->hooknum);
break;
default:
net_info_ratelimited("case %u not handled yet\n", reject->with);
--
1.8.1.2
--
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