tcp: add skb-less helpers to retrieve SYN cookie
This patch allows generation of a SYN cookie before an SKB has been
allocated, as is the case at XDP.
Signed-off-by: Petar Penkov <ppenkov@google.com>
Reviewed-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d57641c..1021739 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1515,6 +1515,21 @@ static struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb)
return sk;
}
+u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
+ struct tcphdr *th, u32 *cookie)
+{
+ u16 mss = 0;
+#ifdef CONFIG_SYN_COOKIES
+ mss = tcp_get_syncookie_mss(&tcp_request_sock_ops,
+ &tcp_request_sock_ipv4_ops, sk, th);
+ if (mss) {
+ *cookie = __cookie_v4_init_sequence(iph, th, &mss);
+ tcp_synq_overflow(sk);
+ }
+#endif
+ return mss;
+}
+
/* The socket must have it's spinlock held when we get
* here, unless it is a TCP_LISTEN socket.
*