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Commit f2020b27 authored by Stanislav Fomichev's avatar Stanislav Fomichev Committed by Pablo Neira Ayuso
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netfilter: ip6t_REJECT: skip checksum verification for outgoing ipv6 packets 



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: default avatarStanislav Fomichev <stfomichev@yandex-team.ru>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 1a869205

net/ipv6/netfilter/ip6t_REJECT.c

+3 −4
Original line number Diff line number Diff line
@@ -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 +88,7 @@ static void send_reset(struct net *net, struct sk_buff *oldskb) 
	}



	/* Check checksum. */

	if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP,

			    skb_checksum(oldskb, tcphoff, otcplen, 0))) {

	if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) {

		pr_debug("TCP checksum is invalid\n");

		return;

	}
@@ -227,7 +226,7 @@ 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);