ipv6: syncookies: do not skip ->iif initialization

When syncookies are in effect, req->iif is left uninitialized.
In case of e.g. link-local addresses the route lookup then fails
and no syn-ack is sent.

Rearrange things so ->iif is also initialized in the syncookie case.

want_cookie can only be true when the isn was zero, thus move the want_cookie
check into the "!isn" branch.

Cc: Glenn Griffin <ggriffin.kernel@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 6 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 5887141ad641..f87534569366 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1272,10 +1272,7 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
         if (!want_cookie)
                 TCP_ECN_create_request(req, tcp_hdr(skb));
 
-        if (want_cookie) {
-                isn = cookie_v6_init_sequence(sk, skb, &req->mss);
-                req->cookie_ts = tmp_opt.tstamp_ok;
-        } else if (!isn) {
+        if (!isn) {
                 if (ipv6_opt_accepted(sk, skb) ||
                     np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
                     np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim) {
@@ -1288,8 +1285,12 @@ static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
                 if (!sk->sk_bound_dev_if &&
                     ipv6_addr_type(&treq->rmt_addr) & IPV6_ADDR_LINKLOCAL)
                         treq->iif = inet6_iif(skb);
-
-                isn = tcp_v6_init_sequence(skb);
+                if (!want_cookie) {
+                        isn = tcp_v6_init_sequence(skb);
+                } else {
+                        isn = cookie_v6_init_sequence(sk, skb, &req->mss);
+                        req->cookie_ts = tmp_opt.tstamp_ok;
+                }
         }
         tcp_rsk(req)->snt_isn = isn;