--- zzzz-none-000/linux-4.19.183/net/ipv6/syncookies.c	2021-03-24 10:07:39.000000000 +0000
+++ bcm63-7530ax-756/linux-4.19.183/net/ipv6/syncookies.c	2023-06-28 08:54:21.000000000 +0000
@@ -20,6 +20,10 @@
 #include <linux/kernel.h>
 #include <net/secure_seq.h>
 #include <net/ipv6.h>
+#if defined(CONFIG_BCM_KF_MPTCP) && defined(CONFIG_BCM_MPTCP)
+#include <net/mptcp.h>
+#include <net/mptcp_v6.h>
+#endif
 #include <net/tcp.h>
 
 #define COOKIEBITS 24	/* Upper bits store count */
@@ -111,7 +115,12 @@
 }
 EXPORT_SYMBOL_GPL(__cookie_v6_init_sequence);
 
+#if !defined(CONFIG_BCM_KF_MPTCP) || !defined(CONFIG_BCM_MPTCP)
 __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mssp)
+#else
+__u32 cookie_v6_init_sequence(struct request_sock *req, const struct sock *sk,
+			      const struct sk_buff *skb, __u16 *mssp)
+#endif
 {
 	const struct ipv6hdr *iph = ipv6_hdr(skb);
 	const struct tcphdr *th = tcp_hdr(skb);
@@ -133,6 +142,9 @@
 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_options_received tcp_opt;
+#if defined(CONFIG_BCM_KF_MPTCP) && defined(CONFIG_BCM_MPTCP)
+	struct mptcp_options_received mopt;
+#endif
 	struct inet_request_sock *ireq;
 	struct tcp_request_sock *treq;
 	struct ipv6_pinfo *np = inet6_sk(sk);
@@ -162,7 +174,12 @@
 
 	/* check for timestamp cookie support */
 	memset(&tcp_opt, 0, sizeof(tcp_opt));
+#if !defined(CONFIG_BCM_KF_MPTCP) || !defined(CONFIG_BCM_MPTCP)
 	tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);
+#else
+	mptcp_init_mp_opt(&mopt);
+	tcp_parse_options(sock_net(sk), skb, &tcp_opt, &mopt, 0, NULL, NULL);
+#endif
 
 	if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
 		tsoff = secure_tcpv6_ts_off(sock_net(sk),
@@ -175,14 +192,35 @@
 		goto out;
 
 	ret = NULL;
+#if !defined(CONFIG_BCM_KF_MPTCP) || !defined(CONFIG_BCM_MPTCP)
 	req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
+#else
+#ifdef CONFIG_MPTCP
+	if (mopt.saw_mpc)
+		req = inet_reqsk_alloc(&mptcp6_request_sock_ops, sk, false);
+	else
+#endif
+		req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
+#endif
 	if (!req)
 		goto out;
 
 	ireq = inet_rsk(req);
+#if defined(CONFIG_BCM_KF_MPTCP) && defined(CONFIG_BCM_MPTCP)
+	ireq->mptcp_rqsk = 0;
+	ireq->saw_mpc = 0;
+#endif
 	treq = tcp_rsk(req);
 	treq->tfo_listener = false;
 
+#if defined(CONFIG_BCM_KF_MPTCP) && defined(CONFIG_BCM_MPTCP)
+	/* Must be done before anything else, as it initializes
+	 * hash_entry of the MPTCP request-sock.
+	 */
+	if (mopt.saw_mpc)
+		mptcp_cookies_reqsk_init(req, &mopt, skb);
+
+#endif
 	if (security_inet_conn_request(sk, skb, req))
 		goto out_free;
 
@@ -246,6 +284,7 @@
 	}
 
 	req->rsk_window_clamp = tp->window_clamp ? :dst_metric(dst, RTAX_WINDOW);
+#if !defined(CONFIG_BCM_KF_MPTCP) || !defined(CONFIG_BCM_MPTCP)
 	/* limit the window selection if the user enforce a smaller rx buffer */
 	full_space = tcp_full_space(sk);
 	if (sk->sk_userlocks & SOCK_RCVBUF_LOCK &&
@@ -256,6 +295,12 @@
 				  &req->rsk_rcv_wnd, &req->rsk_window_clamp,
 				  ireq->wscale_ok, &rcv_wscale,
 				  dst_metric(dst, RTAX_INITRWND));
+#else
+	tp->ops->select_initial_window(sk, tcp_full_space(sk), req->mss,
+				       &req->rsk_rcv_wnd, &req->rsk_window_clamp,
+				       ireq->wscale_ok, &rcv_wscale,
+				       dst_metric(dst, RTAX_INITRWND));
+#endif
 
 	ireq->rcv_wscale = rcv_wscale;
 	ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), dst);