[PATCH net-next v4 5/5] tcp: use drop reasons in cookie check for ipv6

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

Like what I did to ipv4 mode, refine this part: adding more drop
reasons for better tracing.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 net/ipv6/syncookies.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index ea0d9954a29f..f5d7c91abe74 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -190,16 +190,20 @@ struct sock *cookie_v6_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);
 
 	ireq->ir_v6_rmt_addr = ipv6_hdr(skb)->saddr;
 	ireq->ir_v6_loc_addr = ipv6_hdr(skb)->daddr;
 
-	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;
+	}
 
 	if (ipv6_opt_accepted(sk, skb, &TCP_SKB_CB(skb)->header.h6) ||
 	    np->rxopt.bits.rxinfo || np->rxopt.bits.rxoinfo ||
@@ -236,8 +240,10 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 		security_req_classify_flow(req, flowi6_to_flowi_common(&fl6));
 
 		dst = ip6_dst_lookup_flow(net, sk, &fl6, final_p);
-		if (IS_ERR(dst))
+		if (IS_ERR(dst)) {
+			SKB_DR_SET(reason, INVALID_DST);
 			goto out_free;
+		}
 	}
 
 	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
@@ -257,8 +263,10 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	ireq->ecn_ok &= cookie_ecn_ok(net, dst);
 
 	ret = tcp_get_cookie_sock(sk, skb, req, dst);
-	if (!ret)
+	if (!ret) {
+		SKB_DR_SET(reason, COOKIE_NOCHILD);
 		goto out_drop;
+	}
 out:
 	return ret;
 out_free:
-- 
2.37.3