syncookies: add support for ECN

Allows use of ECN when syncookies are in effect by encoding ecn_ok
into the syn-ack tcp timestamp.

While at it, remove a uneeded #ifdef CONFIG_SYN_COOKIES.
With CONFIG_SYN_COOKIES=nm want_cookie is ifdef'd to 0 and gcc
removes the "if (0)".

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 3 deletions

diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 84d818cfae17..09fd34f0dbf2 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -164,6 +164,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
         int mss;
         struct dst_entry *dst;
         __u8 rcv_wscale;
+        bool ecn_ok;
 
         if (!sysctl_tcp_syncookies || !th->ack || th->rst)
                 goto out;
@@ -180,7 +181,7 @@ 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, &hash_location, 0);
 
-        if (!cookie_check_timestamp(&tcp_opt))
+        if (!cookie_check_timestamp(&tcp_opt, &ecn_ok))
                 goto out;
 
         ret = NULL;
@@ -215,7 +216,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 
         req->expires = 0UL;
         req->retrans = 0;
-        ireq->ecn_ok            = 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;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index f87534569366..5ebc27ecebdc 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1269,7 +1269,7 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
         treq = inet6_rsk(req);
         ipv6_addr_copy(&treq->rmt_addr, &ipv6_hdr(skb)->saddr);
         ipv6_addr_copy(&treq->loc_addr, &ipv6_hdr(skb)->daddr);
-        if (!want_cookie)
+        if (!want_cookie || tmp_opt.tstamp_ok)
                 TCP_ECN_create_request(req, tcp_hdr(skb));
 
         if (!isn) {