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authorFlorian Westphal <fw@strlen.de>2014-11-03 19:35:02 +0300
committerDavid S. Miller <davem@davemloft.net>2014-11-05 00:06:09 +0300
commitf1673381b1481a409238d4552a0700d490c5b36c (patch)
tree4d55b02522048fce5110b68e9505b9e996d7eb01 /net/ipv6/syncookies.c
parent274e2da0ecb4d28e3d4e9f029b096e0e8c401a66 (diff)
downloadlinux-f1673381b1481a409238d4552a0700d490c5b36c.tar.xz
syncookies: split cookie_check_timestamp() into two functions
The function cookie_check_timestamp(), both called from IPv4/6 context, is being used to decode the echoed timestamp from the SYN/ACK into TCP options used for follow-up communication with the peer. We can remove ECN handling from that function, split it into a separate one, and simply rename the original function into cookie_decode_options(). cookie_decode_options() just fills in tcp_option struct based on the echoed timestamp received from the peer. Anything that fails in this function will actually discard the request socket. While this is the natural place for decoding options such as ECN which commit 172d69e63c7f ("syncookies: add support for ECN") added, we argue that in particular for ECN handling, it can be checked at a later point in time as the request sock would actually not need to be dropped from this, but just ECN support turned off. Therefore, we split this functionality into cookie_ecn_ok(), which tells us if the timestamp indicates ECN support AND the tcp_ecn sysctl is enabled. This prepares for per-route ECN support: just looking at the tcp_ecn sysctl won't be enough anymore at that point; if the timestamp indicates ECN and sysctl tcp_ecn == 0, we will also need to check the ECN dst metric. This would mean adding a route lookup to cookie_check_timestamp(), which we definitely want to avoid. As we already do a route lookup at a later point in cookie_{v4,v6}_check(), we can simply make use of that as well for the new cookie_ecn_ok() function w/o any additional cost. Joint work with Daniel Borkmann. Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/syncookies.c')
-rw-r--r--net/ipv6/syncookies.c5
1 files changed, 2 insertions, 3 deletions
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index be291baa2ec2..52cc8cb02c0c 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -166,7 +166,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
int mss;
struct dst_entry *dst;
__u8 rcv_wscale;
- bool ecn_ok = false;
if (!sysctl_tcp_syncookies || !th->ack || th->rst)
goto out;
@@ -186,7 +185,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
memset(&tcp_opt, 0, sizeof(tcp_opt));
tcp_parse_options(skb, &tcp_opt, 0, NULL);
- if (!cookie_check_timestamp(&tcp_opt, sock_net(sk), &ecn_ok))
+ if (!cookie_timestamp_decode(&tcp_opt))
goto out;
ret = NULL;
@@ -223,7 +222,6 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
req->expires = 0UL;
req->num_retrans = 0;
- ireq->ecn_ok = ecn_ok;
ireq->snd_wscale = tcp_opt.snd_wscale;
ireq->sack_ok = tcp_opt.sack_ok;
ireq->wscale_ok = tcp_opt.wscale_ok;
@@ -264,6 +262,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
dst_metric(dst, RTAX_INITRWND));
ireq->rcv_wscale = rcv_wscale;
+ ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk));
ret = get_cookie_sock(sk, skb, req, dst);
out: