net/tcp-fastopen: refactor cookie check logic

Refactor the cookie check logic in tcp_send_syn_data() into a function.
This function will be called else where in later changes.

Signed-off-by: Wei Wang <weiwan@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 21 insertions, 0 deletions

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index f51919535ca7..f90e09e1ff4c 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -325,3 +325,24 @@ fastopen:
         *foc = valid_foc;
         return NULL;
 }
+
+bool tcp_fastopen_cookie_check(struct sock *sk, u16 *mss,
+                               struct tcp_fastopen_cookie *cookie)
+{
+        unsigned long last_syn_loss = 0;
+        int syn_loss = 0;
+
+        tcp_fastopen_cache_get(sk, mss, cookie, &syn_loss, &last_syn_loss);
+
+        /* Recurring FO SYN losses: no cookie or data in SYN */
+        if (syn_loss > 1 &&
+            time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) {
+                cookie->len = -1;
+                return false;
+        }
+        if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE) {
+                cookie->len = -1;
+                return true;
+        }
+        return cookie->len > 0;
+}