1 files changed, 43 insertions, 13 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 61045a8886e4..daff93d51342 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4038,24 +4038,17 @@ static void tcp_send_ack_reflect_ect(struct sock *sk, bool accecn_reflector)
 	__tcp_send_ack(sk, tp->rcv_nxt, flags);
 }
 
-/* RFC 5961 7 [ACK Throttling] */
-static void tcp_send_challenge_ack(struct sock *sk, bool accecn_reflector)
+/* Consume one slot from the per-netns RFC 5961 challenge ACK quota.
+ * Returns true if a challenge ACK may be sent.
+ */
+static bool tcp_challenge_ack_allowed(struct net *net)
 {
-	struct tcp_sock *tp = tcp_sk(sk);
-	struct net *net = sock_net(sk);
 	u32 count, now, ack_limit;
 
-	/* First check our per-socket dupack rate limit. */
-	if (__tcp_oow_rate_limited(net,
-				   LINUX_MIB_TCPACKSKIPPEDCHALLENGE,
-				   &tp->last_oow_ack_time))
-		return;
-
 	ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit);
 	if (ack_limit == INT_MAX)
-		goto send_ack;
+		return true;
 
-	/* Then check host-wide RFC 5961 rate limit. */
 	now = jiffies / HZ;
 	if (now != READ_ONCE(net->ipv4.tcp_challenge_timestamp)) {
 		u32 half = (ack_limit + 1) >> 1;
@@ -4067,12 +4060,49 @@ static void tcp_send_challenge_ack(struct sock *sk, bool accecn_reflector)
 	count = READ_ONCE(net->ipv4.tcp_challenge_count);
 	if (count > 0) {
 		WRITE_ONCE(net->ipv4.tcp_challenge_count, count - 1);
-send_ack:
+		return true;
+	}
+	return false;
+}
+
+/* RFC 5961 7 [ACK Throttling] */
+static void tcp_send_challenge_ack(struct sock *sk, bool accecn_reflector)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct net *net = sock_net(sk);
+
+	/* First check our per-socket dupack rate limit. */
+	if (__tcp_oow_rate_limited(net,
+				   LINUX_MIB_TCPACKSKIPPEDCHALLENGE,
+				   &tp->last_oow_ack_time))
+		return;
+
+	/* Then check the per-netns RFC 5961 rate limit. */
+	if (tcp_challenge_ack_allowed(net)) {
 		NET_INC_STATS(net, LINUX_MIB_TCPCHALLENGEACK);
 		tcp_send_ack_reflect_ect(sk, accecn_reflector);
 	}
 }
 
+/* Send a challenge ACK from a SYN-RECEIVED request socket. Uses
+ * __tcp_oow_rate_limited() directly so that an RST carrying payload
+ * cannot bypass the per-request rate limit.
+ */
+void tcp_reqsk_send_challenge_ack(struct sock *sk, struct sk_buff *skb,
+				  struct request_sock *req)
+{
+	struct net *net = sock_net(sk);
+
+	if (__tcp_oow_rate_limited(net, LINUX_MIB_TCPACKSKIPPEDCHALLENGE,
+				   &tcp_rsk(req)->last_oow_ack_time))
+		return;
+
+	if (tcp_challenge_ack_allowed(net)) {
+		NET_INC_STATS(net, LINUX_MIB_TCPCHALLENGEACK);
+		req->rsk_ops->send_ack(sk, skb, req);
+	}
+}
+
 static void tcp_store_ts_recent(struct tcp_sock *tp)
 {
 	tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;