| Message ID | 20130828131438.24364.25004.stgit@dragon |
|---|---|
| State | Accepted |
| Headers | show |
On Wed, Aug 28, 2013 at 03:14:38PM +0200, Jesper Dangaard Brouer wrote: > Its seems Patrick missed to incoorporate some of my requested changes > during review v2 of SYNPROXY netfilter module. > > Which were, to avoid SYN+ACK packets to enter the path, meant for the > ACK packet from the client (from the 3WHS). > > Further there were a bug in ip6t_SYNPROXY.c, for matching SYN packets > that didn't exclude the ACK flag. > > Go a step further with SYN packet/flag matching by excluding flags > ACK+FIN+RST, in both IPv4 and IPv6 modules. > > > The intented usage of SYNPROXY is as follows: > (gracefully describing usage in commit) > > iptables -t raw -A PREROUTING -i eth0 -p tcp --dport 80 --syn -j NOTRACK > iptables -A INPUT -i eth0 -p tcp --dport 80 -m state UNTRACKED,INVALID \ > -j SYNPROXY --sack-perm --timestamp --mss 1480 --wscale 7 --ecn > > echo 0 > /proc/sys/net/netfilter/nf_conntrack_tcp_loose > > This does filter SYN flags early, for packets in the UNTRACKED state, > but packets in the INVALID state with other TCP flags could still > reach the module, thus this stricter flag matching is still needed. > > Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Acked-by: Patrick McHardy <kaber@trash.net> -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c b/net/ipv4/netfilter/ipt_SYNPROXY.c index 94371db..90e489e 100644 --- a/net/ipv4/netfilter/ipt_SYNPROXY.c +++ b/net/ipv4/netfilter/ipt_SYNPROXY.c @@ -269,7 +269,7 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par) synproxy_parse_options(skb, par->thoff, th, &opts); - if (th->syn && !th->ack) { + if (th->syn && !(th->ack || th->fin || th->rst)) { /* Initial SYN from client */ this_cpu_inc(snet->stats->syn_received); @@ -285,7 +285,7 @@ synproxy_tg4(struct sk_buff *skb, const struct xt_action_param *par) XT_SYNPROXY_OPT_ECN); synproxy_send_client_synack(skb, th, &opts); - } else if (th->ack && !(th->fin || th->rst)) + } else if (th->ack && !(th->fin || th->rst || th->syn)) /* ACK from client */ synproxy_recv_client_ack(snet, skb, th, &opts, ntohl(th->seq)); diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c b/net/ipv6/netfilter/ip6t_SYNPROXY.c index 4270a9b..a5af0bf 100644 --- a/net/ipv6/netfilter/ip6t_SYNPROXY.c +++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c @@ -284,7 +284,7 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par) synproxy_parse_options(skb, par->thoff, th, &opts); - if (th->syn) { + if (th->syn && !(th->ack || th->fin || th->rst)) { /* Initial SYN from client */ this_cpu_inc(snet->stats->syn_received); @@ -300,7 +300,7 @@ synproxy_tg6(struct sk_buff *skb, const struct xt_action_param *par) XT_SYNPROXY_OPT_ECN); synproxy_send_client_synack(skb, th, &opts); - } else if (th->ack && !(th->fin || th->rst)) + } else if (th->ack && !(th->fin || th->rst || th->syn)) /* ACK from client */ synproxy_recv_client_ack(snet, skb, th, &opts, ntohl(th->seq));
Its seems Patrick missed to incoorporate some of my requested changes during review v2 of SYNPROXY netfilter module. Which were, to avoid SYN+ACK packets to enter the path, meant for the ACK packet from the client (from the 3WHS). Further there were a bug in ip6t_SYNPROXY.c, for matching SYN packets that didn't exclude the ACK flag. Go a step further with SYN packet/flag matching by excluding flags ACK+FIN+RST, in both IPv4 and IPv6 modules. The intented usage of SYNPROXY is as follows: (gracefully describing usage in commit) iptables -t raw -A PREROUTING -i eth0 -p tcp --dport 80 --syn -j NOTRACK iptables -A INPUT -i eth0 -p tcp --dport 80 -m state UNTRACKED,INVALID \ -j SYNPROXY --sack-perm --timestamp --mss 1480 --wscale 7 --ecn echo 0 > /proc/sys/net/netfilter/nf_conntrack_tcp_loose This does filter SYN flags early, for packets in the UNTRACKED state, but packets in the INVALID state with other TCP flags could still reach the module, thus this stricter flag matching is still needed. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> --- net/ipv4/netfilter/ipt_SYNPROXY.c | 4 ++-- net/ipv6/netfilter/ip6t_SYNPROXY.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html