netdev - [PATCH net-next v10 04/10] tcp: directly drop skb in cookie check for ipv6

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Date: Mon, 26 Feb 2024 11:22:21 +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 v10 04/10] tcp: directly drop skb in cookie check for ipv6

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

Like previous patch does, only moving skb drop logical code to
cookie_v6_check() for later refinement.

Signed-off-by: Jason Xing <kernelxing@...cent.com>
Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Reviewed-by: David Ahern <dsahern@...nel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>
--
v9
Link: https://lore.kernel.org/netdev/c5640fc4-16dc-4058-97c6-bd84bae4fda1@kernel.org/
1. add reviewed-by tag (David)

v8
Link: https://lore.kernel.org/netdev/CANn89iL8M=1vFdZ1hBb4POuz+MKQ50fmBAewfbowEH3jpEtpZQ@mail.gmail.com/
1. add reviewed-by tag (Eric)

v7:
Link: https://lore.kernel.org/all/20240219043815.98410-1-kuniyu@amazon.com/
1. refine the code (by removing redundant check), no functional changes. (Kuniyuki)

v6
Link: https://lore.kernel.org/all/c987d2c79e4a4655166eb8eafef473384edb37fb.camel@redhat.com/
Link: https://lore.kernel.org/all/CAL+tcoAgSjwsmFnDh_Gs9ZgMi-y5awtVx+4VhJPNRADjo7LLSA@mail.gmail.com/
1. take one case into consideration, behave like old days, or else it will trigger errors.

v5
Link: https://lore.kernel.org/netdev/CANn89iKz7=1q7e8KY57Dn3ED7O=RCOfLxoHQKO4eNXnZa1OPWg@mail.gmail.com/
1. avoid duplication of these opt_skb tests/actions (Eric)
---
 net/ipv6/syncookies.c | 4 ++++
 net/ipv6/tcp_ipv6.c   | 5 +----
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 6b9c69278819..ea0d9954a29f 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -177,6 +177,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 	struct sock *ret = sk;
 	__u8 rcv_wscale;
 	int full_space;
+	SKB_DR(reason);
 
 	if (!READ_ONCE(net->ipv4.sysctl_tcp_syncookies) ||
 	    !th->ack || th->rst)
@@ -256,10 +257,13 @@ 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)
+		goto out_drop;
 out:
 	return ret;
 out_free:
 	reqsk_free(req);
 out_drop:
+	kfree_skb_reason(skb, reason);
 	return NULL;
 }
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 57b25b1fc9d9..0c180bb8187f 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1653,11 +1653,8 @@ int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 	if (sk->sk_state == TCP_LISTEN) {
 		struct sock *nsk = tcp_v6_cookie_check(sk, skb);
 
-		if (!nsk)
-			goto discard;
-
 		if (nsk != sk) {
-			if (tcp_child_process(sk, nsk, skb))
+			if (nsk && tcp_child_process(sk, nsk, skb))
 				goto reset;
 			if (opt_skb)
 				__kfree_skb(opt_skb);
-- 
2.37.3