Subject: [PATCH net-next v4 3/5] tcp: use drop reasons in cookie check for ipv4

From: Jason Xing <[email-masked]>
Date: Tue, 13 Feb 2024 21:42:03 +0800

From: Jason Xing <[email-masked]>

Now it's time to use the prepared definitions to refine this part.
Four reasons used might enough for now, I think.

Signed-off-by: Jason Xing <[email-masked]>
---
 net/ipv4/syncookies.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 38f331da6677..07e201cc3d6a 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -421,8 +421,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 		if (IS_ERR(req))
 			goto out;
 	}
-	if (!req)
+	if (!req) {
+		SKB_DR_SET(reason, NO_REQSK_ALLOC);
 		goto out_drop;
+	}
 
 	ireq = inet_rsk(req);
 
@@ -434,8 +436,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	 */
 	RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(net, skb));
 
-	if (security_inet_conn_request(sk, skb, req))
+	if (security_inet_conn_request(sk, skb, req)) {
+		SKB_DR_SET(reason, SECURITY_HOOK);
 		goto out_free;
+	}
 
 	tcp_ao_syncookie(sk, skb, req, AF_INET);
 
@@ -452,8 +456,10 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 			   ireq->ir_loc_addr, th->source, th->dest, sk->sk_uid);
 	security_req_classify_flow(req, flowi4_to_flowi_common(&fl4));
 	rt = ip_route_output_key(net, &fl4);
-	if (IS_ERR(rt))
+	if (IS_ERR(rt)) {
+		SKB_DR_SET(reason, IP_ROUTEOUTPUTKEY);
 		goto out_free;
+	}
 
 	/* Try to redo what tcp_v4_send_synack did. */
 	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
@@ -476,10 +482,12 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	/* ip_queue_xmit() depends on our flow being setup
 	 * Normal sockets get it right from inet_csk_route_child_sock()
 	 */
-	if (ret)
+	if (ret) {
 		inet_sk(ret)->cork.fl.u.ip4 = fl4;
-	else
+	} else {
+		SKB_DR_SET(reason, COOKIE_NOCHILD);
 		goto out_drop;
+	}
 out:
 	return ret;
 out_free:
-- 
2.37.3