netdev - [PATCH net-next v8 02/10] tcp: directly drop skb in cookie check for ipv4

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Message-Id: <20240222113003.67558-3-kerneljasonxing@gmail.com>
Date: Thu, 22 Feb 2024 19:29:55 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	dsahern@...nel.org,
	kuniyu@...zon.com
Cc: netdev@...r.kernel.org,
	kerneljasonxing@...il.com,
	Jason Xing <kernelxing@...cent.com>
Subject: [PATCH net-next v8 02/10] tcp: directly drop skb in cookie check for ipv4

From: Jason Xing <kernelxing@...cent.com>

Only move the skb drop from tcp_v4_do_rcv() to cookie_v4_check() itself,
no other changes made. It can help us refine the specific drop reasons
later.

Signed-off-by: Jason Xing <kernelxing@...cent.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
--
v8
Link: https://lore.kernel.org/netdev/CANn89i+foA-AW3KCNw232eCC5GDi_3O0JG-mpvyiQJYuxKxnRA@mail.gmail.com/
1. add reviewed-by tag (Eric)

v7
Link: https://lore.kernel.org/all/20240219041350.95304-1-kuniyu@amazon.com/
1. add reviewed-by tag (Kuniyuki)
---
 net/ipv4/syncookies.c | 4 ++++
 net/ipv4/tcp_ipv4.c   | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index be88bf586ff9..38f331da6677 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -408,6 +408,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	struct rtable *rt;
 	__u8 rcv_wscale;
 	int full_space;
+	SKB_DR(reason);
 
 	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
 	    !th->ack || th->rst)
@@ -477,10 +478,13 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
 	 */
 	if (ret)
 		inet_sk(ret)->cork.fl.u.ip4 = fl4;
+	else
+		goto out_drop;
 out:
 	return ret;
 out_free:
 	reqsk_free(req);
 out_drop:
+	kfree_skb_reason(skb, reason);
 	return NULL;
 }
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 0c50c5a32b84..0a944e109088 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1915,7 +1915,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 		struct sock *nsk = tcp_v4_cookie_check(sk, skb);
 
 		if (!nsk)
-			goto discard;
+			return 0;
 		if (nsk != sk) {
 			if (tcp_child_process(sk, nsk, skb)) {
 				rsk = nsk;
-- 
2.37.3