diff --git a/include/net/tcp.h b/include/net/tcp.h
index e5cf514ba118e688ce3b3da66f696abd47e1d10f..fb7e153aecc54db07d5294175bdabfacdb6ea70b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -414,6 +414,16 @@ void tcp_parse_options(const struct net *net, const struct sk_buff *skb,
 		       int estab, struct tcp_fastopen_cookie *foc);
 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
 
+/*
+ *	BPF SKB-less helpers
+ */
+u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
+			 struct tcphdr *th, u32 *cookie);
+u16 tcp_v6_get_syncookie(struct sock *sk, struct ipv6hdr *iph,
+			 struct tcphdr *th, u32 *cookie);
+u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
+			  const struct tcp_request_sock_ops *af_ops,
+			  struct sock *sk, struct tcphdr *th);
 /*
  *	TCP v4 functions exported for the inet6 API
  */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 6bbef0c7f5853307b452516e960585a0a5514325..4393bd4b241973c1ad82edb70a40b63517a7f9ce 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2714,6 +2714,33 @@ union bpf_attr {
  *		**-EPERM** if no permission to send the *sig*.
  *
  *		**-EAGAIN** if bpf program can try again.
+ *
+ * s64 bpf_tcp_gen_syncookie(struct bpf_sock *sk, void *iph, u32 iph_len, struct tcphdr *th, u32 th_len)
+ *	Description
+ *		Try to issue a SYN cookie for the packet with corresponding
+ *		IP/TCP headers, *iph* and *th*, on the listening socket in *sk*.
+ *
+ *		*iph* points to the start of the IPv4 or IPv6 header, while
+ *		*iph_len* contains **sizeof**\ (**struct iphdr**) or
+ *		**sizeof**\ (**struct ip6hdr**).
+ *
+ *		*th* points to the start of the TCP header, while *th_len*
+ *		contains the length of the TCP header.
+ *
+ *	Return
+ *		On success, lower 32 bits hold the generated SYN cookie in
+ *		followed by 16 bits which hold the MSS value for that cookie,
+ *		and the top 16 bits are unused.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EINVAL** SYN cookie cannot be issued due to error
+ *
+ *		**-ENOENT** SYN cookie should not be issued (no SYN flood)
+ *
+ *		**-EOPNOTSUPP** kernel configuration does not enable SYN cookies
+ *
+ *		**-EPROTONOSUPPORT** IP packet version is not 4 or 6
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -2825,7 +2852,8 @@ union bpf_attr {
 	FN(strtoul),			\
 	FN(sk_storage_get),		\
 	FN(sk_storage_delete),		\
-	FN(send_signal),
+	FN(send_signal),		\
+	FN(tcp_gen_syncookie),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
diff --git a/net/core/filter.c b/net/core/filter.c
index 1eee70f80fbad224fe4eb64b4b9f7eca371da956..5a2707918629bc1112e3057f15c6e6da5d7dae64 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5855,6 +5855,75 @@ static const struct bpf_func_proto bpf_tcp_check_syncookie_proto = {
 	.arg5_type	= ARG_CONST_SIZE,
 };
 
+BPF_CALL_5(bpf_tcp_gen_syncookie, struct sock *, sk, void *, iph, u32, iph_len,
+	   struct tcphdr *, th, u32, th_len)
+{
+#ifdef CONFIG_SYN_COOKIES
+	u32 cookie;
+	u16 mss;
+
+	if (unlikely(th_len < sizeof(*th) || th_len != th->doff * 4))
+		return -EINVAL;
+
+	if (sk->sk_protocol != IPPROTO_TCP || sk->sk_state != TCP_LISTEN)
+		return -EINVAL;
+
+	if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies)
+		return -ENOENT;
+
+	if (!th->syn || th->ack || th->fin || th->rst)
+		return -EINVAL;
+
+	if (unlikely(iph_len < sizeof(struct iphdr)))
+		return -EINVAL;
+
+	/* Both struct iphdr and struct ipv6hdr have the version field at the
+	 * same offset so we can cast to the shorter header (struct iphdr).
+	 */
+	switch (((struct iphdr *)iph)->version) {
+	case 4:
+		if (sk->sk_family == AF_INET6 && sk->sk_ipv6only)
+			return -EINVAL;
+
+		mss = tcp_v4_get_syncookie(sk, iph, th, &cookie);
+		break;
+
+#if IS_BUILTIN(CONFIG_IPV6)
+	case 6:
+		if (unlikely(iph_len < sizeof(struct ipv6hdr)))
+			return -EINVAL;
+
+		if (sk->sk_family != AF_INET6)
+			return -EINVAL;
+
+		mss = tcp_v6_get_syncookie(sk, iph, th, &cookie);
+		break;
+#endif /* CONFIG_IPV6 */
+
+	default:
+		return -EPROTONOSUPPORT;
+	}
+	if (mss <= 0)
+		return -ENOENT;
+
+	return cookie | ((u64)mss << 32);
+#else
+	return -EOPNOTSUPP;
+#endif /* CONFIG_SYN_COOKIES */
+}
+
+static const struct bpf_func_proto bpf_tcp_gen_syncookie_proto = {
+	.func		= bpf_tcp_gen_syncookie,
+	.gpl_only	= true, /* __cookie_v*_init_sequence() is GPL */
+	.pkt_access	= true,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_SOCK_COMMON,
+	.arg2_type	= ARG_PTR_TO_MEM,
+	.arg3_type	= ARG_CONST_SIZE,
+	.arg4_type	= ARG_PTR_TO_MEM,
+	.arg5_type	= ARG_CONST_SIZE,
+};
+
 #endif /* CONFIG_INET */
 
 bool bpf_helper_changes_pkt_data(void *func)
@@ -6144,6 +6213,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_tcp_check_syncookie_proto;
 	case BPF_FUNC_skb_ecn_set_ce:
 		return &bpf_skb_ecn_set_ce_proto;
+	case BPF_FUNC_tcp_gen_syncookie:
+		return &bpf_tcp_gen_syncookie_proto;
 #endif
 	default:
 		return bpf_base_func_proto(func_id);
@@ -6183,6 +6254,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_xdp_skc_lookup_tcp_proto;
 	case BPF_FUNC_tcp_check_syncookie:
 		return &bpf_tcp_check_syncookie_proto;
+	case BPF_FUNC_tcp_gen_syncookie:
+		return &bpf_tcp_gen_syncookie_proto;
 #endif
 	default:
 		return bpf_base_func_proto(func_id);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c21e8a22fb3bb39d06eb3ee7eb4cfae5066b6f48..706cbb3b2986b8d31664e80e2a4cb9d9f29b4bbd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3782,6 +3782,49 @@ static void smc_parse_options(const struct tcphdr *th,
 #endif
 }
 
+/* Try to parse the MSS option from the TCP header. Return 0 on failure, clamped
+ * value on success.
+ */
+static u16 tcp_parse_mss_option(const struct tcphdr *th, u16 user_mss)
+{
+	const unsigned char *ptr = (const unsigned char *)(th + 1);
+	int length = (th->doff * 4) - sizeof(struct tcphdr);
+	u16 mss = 0;
+
+	while (length > 0) {
+		int opcode = *ptr++;
+		int opsize;
+
+		switch (opcode) {
+		case TCPOPT_EOL:
+			return mss;
+		case TCPOPT_NOP:	/* Ref: RFC 793 section 3.1 */
+			length--;
+			continue;
+		default:
+			if (length < 2)
+				return mss;
+			opsize = *ptr++;
+			if (opsize < 2) /* "silly options" */
+				return mss;
+			if (opsize > length)
+				return mss;	/* fail on partial options */
+			if (opcode == TCPOPT_MSS && opsize == TCPOLEN_MSS) {
+				u16 in_mss = get_unaligned_be16(ptr);
+
+				if (in_mss) {
+					if (user_mss && user_mss < in_mss)
+						in_mss = user_mss;
+					mss = in_mss;
+				}
+			}
+			ptr += opsize - 2;
+			length -= opsize;
+		}
+	}
+	return mss;
+}
+
 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
  * But, this can also be called on packets in the established flow when
  * the fast version below fails.
@@ -6422,9 +6465,7 @@ EXPORT_SYMBOL(inet_reqsk_alloc);
 /*
  * Return true if a syncookie should be sent
  */
-static bool tcp_syn_flood_action(const struct sock *sk,
-				 const struct sk_buff *skb,
-				 const char *proto)
+static bool tcp_syn_flood_action(const struct sock *sk, const char *proto)
 {
 	struct request_sock_queue *queue = &inet_csk(sk)->icsk_accept_queue;
 	const char *msg = "Dropping request";
@@ -6444,7 +6485,7 @@ static bool tcp_syn_flood_action(const struct sock *sk,
 	    net->ipv4.sysctl_tcp_syncookies != 2 &&
 	    xchg(&queue->synflood_warned, 1) == 0)
 		net_info_ratelimited("%s: Possible SYN flooding on port %d. %s.  Check SNMP counters.\n",
-				     proto, ntohs(tcp_hdr(skb)->dest), msg);
+				     proto, sk->sk_num, msg);
 
 	return want_cookie;
 }
@@ -6466,6 +6507,36 @@ static void tcp_reqsk_record_syn(const struct sock *sk,
 	}
 }
 
+/* If a SYN cookie is required and supported, returns a clamped MSS value to be
+ * used for SYN cookie generation.
+ */
+u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
+			  const struct tcp_request_sock_ops *af_ops,
+			  struct sock *sk, struct tcphdr *th)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	u16 mss;
+
+	if (sock_net(sk)->ipv4.sysctl_tcp_syncookies != 2 &&
+	    !inet_csk_reqsk_queue_is_full(sk))
+		return 0;
+
+	if (!tcp_syn_flood_action(sk, rsk_ops->slab_name))
+		return 0;
+
+	if (sk_acceptq_is_full(sk)) {
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
+		return 0;
+	}
+
+	mss = tcp_parse_mss_option(th, tp->rx_opt.user_mss);
+	if (!mss)
+		mss = af_ops->mss_clamp;
+
+	return mss;
+}
+EXPORT_SYMBOL_GPL(tcp_get_syncookie_mss);
+
 int tcp_conn_request(struct request_sock_ops *rsk_ops,
 		     const struct tcp_request_sock_ops *af_ops,
 		     struct sock *sk, struct sk_buff *skb)
@@ -6487,7 +6558,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 	 */
 	if ((net->ipv4.sysctl_tcp_syncookies == 2 ||
 	     inet_csk_reqsk_queue_is_full(sk)) && !isn) {
-		want_cookie = tcp_syn_flood_action(sk, skb, rsk_ops->slab_name);
+		want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name);
 		if (!want_cookie)
 			goto drop;
 	}
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d57641cb3477d0c573e6648fccfc77ce52f52660..10217393cda65ccb26b454f85501095f28b9126c 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1515,6 +1515,21 @@ static struct sock *tcp_v4_cookie_check(struct sock *sk, struct sk_buff *skb)
 	return sk;
 }
 
+u16 tcp_v4_get_syncookie(struct sock *sk, struct iphdr *iph,
+			 struct tcphdr *th, u32 *cookie)
+{
+	u16 mss = 0;
+#ifdef CONFIG_SYN_COOKIES
+	mss = tcp_get_syncookie_mss(&tcp_request_sock_ops,
+				    &tcp_request_sock_ipv4_ops, sk, th);
+	if (mss) {
+		*cookie = __cookie_v4_init_sequence(iph, th, &mss);
+		tcp_synq_overflow(sk);
+	}
+#endif
+	return mss;
+}
+
 /* The socket must have it's spinlock held when we get
  * here, unless it is a TCP_LISTEN socket.
  *
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 5da069e91cacca4e84a3e41dae4746c9d38fcc46..87f44d3250ee6844777a000760326d6ad6831de6 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1063,6 +1063,21 @@ static struct sock *tcp_v6_cookie_check(struct sock *sk, struct sk_buff *skb)
 	return sk;
 }
 
+u16 tcp_v6_get_syncookie(struct sock *sk, struct ipv6hdr *iph,
+			 struct tcphdr *th, u32 *cookie)
+{
+	u16 mss = 0;
+#ifdef CONFIG_SYN_COOKIES
+	mss = tcp_get_syncookie_mss(&tcp6_request_sock_ops,
+				    &tcp_request_sock_ipv6_ops, sk, th);
+	if (mss) {
+		*cookie = __cookie_v6_init_sequence(iph, th, &mss);
+		tcp_synq_overflow(sk);
+	}
+#endif
+	return mss;
+}
+
 static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 {
 	if (skb->protocol == htons(ETH_P_IP))
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 21d0f6863df3c8af099f38a32f3e6b94f8250937..4393bd4b241973c1ad82edb70a40b63517a7f9ce 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1572,8 +1572,11 @@ union bpf_attr {
  * 		but this is only implemented for native XDP (with driver
  * 		support) as of this writing).
  *
- * 		All values for *flags* are reserved for future usage, and must
- * 		be left at zero.
+ * 		The lower two bits of *flags* are used as the return code if
+ * 		the map lookup fails. This is so that the return value can be
+ * 		one of the XDP program return codes up to XDP_TX, as chosen by
+ * 		the caller. Any higher bits in the *flags* argument must be
+ * 		unset.
  *
  * 		When used to redirect packets to net devices, this helper
  * 		provides a high performance increase over **bpf_redirect**\ ().
@@ -2711,6 +2714,33 @@ union bpf_attr {
  *		**-EPERM** if no permission to send the *sig*.
  *
  *		**-EAGAIN** if bpf program can try again.
+ *
+ * s64 bpf_tcp_gen_syncookie(struct bpf_sock *sk, void *iph, u32 iph_len, struct tcphdr *th, u32 th_len)
+ *	Description
+ *		Try to issue a SYN cookie for the packet with corresponding
+ *		IP/TCP headers, *iph* and *th*, on the listening socket in *sk*.
+ *
+ *		*iph* points to the start of the IPv4 or IPv6 header, while
+ *		*iph_len* contains **sizeof**\ (**struct iphdr**) or
+ *		**sizeof**\ (**struct ip6hdr**).
+ *
+ *		*th* points to the start of the TCP header, while *th_len*
+ *		contains the length of the TCP header.
+ *
+ *	Return
+ *		On success, lower 32 bits hold the generated SYN cookie in
+ *		followed by 16 bits which hold the MSS value for that cookie,
+ *		and the top 16 bits are unused.
+ *
+ *		On failure, the returned value is one of the following:
+ *
+ *		**-EINVAL** SYN cookie cannot be issued due to error
+ *
+ *		**-ENOENT** SYN cookie should not be issued (no SYN flood)
+ *
+ *		**-EOPNOTSUPP** kernel configuration does not enable SYN cookies
+ *
+ *		**-EPROTONOSUPPORT** IP packet version is not 4 or 6
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -2822,7 +2852,8 @@ union bpf_attr {
 	FN(strtoul),			\
 	FN(sk_storage_get),		\
 	FN(sk_storage_delete),		\
-	FN(send_signal),
+	FN(send_signal),		\
+	FN(tcp_gen_syncookie),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call
diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index f804f210244eadf0deb361879f74f6c268c1b34e..120aa86c58d35298b8ecb0bf130ced3210b88b2a 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -228,6 +228,9 @@ static void *(*bpf_sk_storage_get)(void *map, struct bpf_sock *sk,
 static int (*bpf_sk_storage_delete)(void *map, struct bpf_sock *sk) =
 	(void *)BPF_FUNC_sk_storage_delete;
 static int (*bpf_send_signal)(unsigned sig) = (void *)BPF_FUNC_send_signal;
+static long long (*bpf_tcp_gen_syncookie)(struct bpf_sock *sk, void *ip,
+					  int ip_len, void *tcp, int tcp_len) =
+	(void *) BPF_FUNC_tcp_gen_syncookie;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions
diff --git a/tools/testing/selftests/bpf/progs/test_tcp_check_syncookie_kern.c b/tools/testing/selftests/bpf/progs/test_tcp_check_syncookie_kern.c
index 1ab095bcacd844ea1ed57ad728b166a425e363ad..d8803dfa8d32f0016327c62dbffd35061e1c2598 100644
--- a/tools/testing/selftests/bpf/progs/test_tcp_check_syncookie_kern.c
+++ b/tools/testing/selftests/bpf/progs/test_tcp_check_syncookie_kern.c
@@ -19,10 +19,29 @@
 struct bpf_map_def SEC("maps") results = {
 	.type = BPF_MAP_TYPE_ARRAY,
 	.key_size = sizeof(__u32),
-	.value_size = sizeof(__u64),
-	.max_entries = 1,
+	.value_size = sizeof(__u32),
+	.max_entries = 3,
 };
 
+static __always_inline __s64 gen_syncookie(void *data_end, struct bpf_sock *sk,
+					   void *iph, __u32 ip_size,
+					   struct tcphdr *tcph)
+{
+	__u32 thlen = tcph->doff * 4;
+
+	if (tcph->syn && !tcph->ack) {
+		// packet should only have an MSS option
+		if (thlen != 24)
+			return 0;
+
+		if ((void *)tcph + thlen > data_end)
+			return 0;
+
+		return bpf_tcp_gen_syncookie(sk, iph, ip_size, tcph, thlen);
+	}
+	return 0;
+}
+
 static __always_inline void check_syncookie(void *ctx, void *data,
 					    void *data_end)
 {
@@ -33,8 +52,10 @@ static __always_inline void check_syncookie(void *ctx, void *data,
 	struct ipv6hdr *ipv6h;
 	struct tcphdr *tcph;
 	int ret;
+	__u32 key_mss = 2;
+	__u32 key_gen = 1;
 	__u32 key = 0;
-	__u64 value = 1;
+	__s64 seq_mss;
 
 	ethh = data;
 	if (ethh + 1 > data_end)
@@ -66,6 +87,9 @@ static __always_inline void check_syncookie(void *ctx, void *data,
 		if (sk->state != BPF_TCP_LISTEN)
 			goto release;
 
+		seq_mss = gen_syncookie(data_end, sk, ipv4h, sizeof(*ipv4h),
+					tcph);
+
 		ret = bpf_tcp_check_syncookie(sk, ipv4h, sizeof(*ipv4h),
 					      tcph, sizeof(*tcph));
 		break;
@@ -95,6 +119,9 @@ static __always_inline void check_syncookie(void *ctx, void *data,
 		if (sk->state != BPF_TCP_LISTEN)
 			goto release;
 
+		seq_mss = gen_syncookie(data_end, sk, ipv6h, sizeof(*ipv6h),
+					tcph);
+
 		ret = bpf_tcp_check_syncookie(sk, ipv6h, sizeof(*ipv6h),
 					      tcph, sizeof(*tcph));
 		break;
@@ -103,8 +130,19 @@ static __always_inline void check_syncookie(void *ctx, void *data,
 		return;
 	}
 
-	if (ret == 0)
-		bpf_map_update_elem(&results, &key, &value, 0);
+	if (seq_mss > 0) {
+		__u32 cookie = (__u32)seq_mss;
+		__u32 mss = seq_mss >> 32;
+
+		bpf_map_update_elem(&results, &key_gen, &cookie, 0);
+		bpf_map_update_elem(&results, &key_mss, &mss, 0);
+	}
+
+	if (ret == 0) {
+		__u32 cookie = bpf_ntohl(tcph->ack_seq) - 1;
+
+		bpf_map_update_elem(&results, &key, &cookie, 0);
+	}
 
 release:
 	bpf_sk_release(sk);
diff --git a/tools/testing/selftests/bpf/test_tcp_check_syncookie.sh b/tools/testing/selftests/bpf/test_tcp_check_syncookie.sh
index d48e51716d196b360c3919822a24be97c7147440..9b3617d770a525875bf6a0d6d6d2f27553267029 100755
--- a/tools/testing/selftests/bpf/test_tcp_check_syncookie.sh
+++ b/tools/testing/selftests/bpf/test_tcp_check_syncookie.sh
@@ -37,6 +37,9 @@ setup()
 	ns1_exec ip link set lo up
 
 	ns1_exec sysctl -w net.ipv4.tcp_syncookies=2
+	ns1_exec sysctl -w net.ipv4.tcp_window_scaling=0
+	ns1_exec sysctl -w net.ipv4.tcp_timestamps=0
+	ns1_exec sysctl -w net.ipv4.tcp_sack=0
 
 	wait_for_ip 127.0.0.1
 	wait_for_ip ::1
diff --git a/tools/testing/selftests/bpf/test_tcp_check_syncookie_user.c b/tools/testing/selftests/bpf/test_tcp_check_syncookie_user.c
index 87829c86c7469564a5b3ed06c2fcdc961e7cca12..b9e991d431556ce84064e479bb05e35ac7eea4a7 100644
--- a/tools/testing/selftests/bpf/test_tcp_check_syncookie_user.c
+++ b/tools/testing/selftests/bpf/test_tcp_check_syncookie_user.c
@@ -2,6 +2,7 @@
 // Copyright (c) 2018 Facebook
 // Copyright (c) 2019 Cloudflare
 
+#include <limits.h>
 #include <string.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -77,7 +78,7 @@ static int connect_to_server(int server_fd)
 	return fd;
 }
 
-static int get_map_fd_by_prog_id(int prog_id)
+static int get_map_fd_by_prog_id(int prog_id, bool *xdp)
 {
 	struct bpf_prog_info info = {};
 	__u32 info_len = sizeof(info);
@@ -104,6 +105,8 @@ static int get_map_fd_by_prog_id(int prog_id)
 		goto err;
 	}
 
+	*xdp = info.type == BPF_PROG_TYPE_XDP;
+
 	map_fd = bpf_map_get_fd_by_id(map_ids[0]);
 	if (map_fd < 0)
 		log_err("Failed to get fd by map id %d", map_ids[0]);
@@ -113,18 +116,32 @@ static int get_map_fd_by_prog_id(int prog_id)
 	return map_fd;
 }
 
-static int run_test(int server_fd, int results_fd)
+static int run_test(int server_fd, int results_fd, bool xdp)
 {
 	int client = -1, srv_client = -1;
 	int ret = 0;
 	__u32 key = 0;
-	__u64 value = 0;
+	__u32 key_gen = 1;
+	__u32 key_mss = 2;
+	__u32 value = 0;
+	__u32 value_gen = 0;
+	__u32 value_mss = 0;
 
 	if (bpf_map_update_elem(results_fd, &key, &value, 0) < 0) {
 		log_err("Can't clear results");
 		goto err;
 	}
 
+	if (bpf_map_update_elem(results_fd, &key_gen, &value_gen, 0) < 0) {
+		log_err("Can't clear results");
+		goto err;
+	}
+
+	if (bpf_map_update_elem(results_fd, &key_mss, &value_mss, 0) < 0) {
+		log_err("Can't clear results");
+		goto err;
+	}
+
 	client = connect_to_server(server_fd);
 	if (client == -1)
 		goto err;
@@ -140,8 +157,35 @@ static int run_test(int server_fd, int results_fd)
 		goto err;
 	}
 
-	if (value != 1) {
-		log_err("Didn't match syncookie: %llu", value);
+	if (value == 0) {
+		log_err("Didn't match syncookie: %u", value);
+		goto err;
+	}
+
+	if (bpf_map_lookup_elem(results_fd, &key_gen, &value_gen) < 0) {
+		log_err("Can't lookup result");
+		goto err;
+	}
+
+	if (xdp && value_gen == 0) {
+		// SYN packets do not get passed through generic XDP, skip the
+		// rest of the test.
+		printf("Skipping XDP cookie check\n");
+		goto out;
+	}
+
+	if (bpf_map_lookup_elem(results_fd, &key_mss, &value_mss) < 0) {
+		log_err("Can't lookup result");
+		goto err;
+	}
+
+	if (value != value_gen) {
+		log_err("BPF generated cookie does not match kernel one");
+		goto err;
+	}
+
+	if (value_mss < 536 || value_mss > USHRT_MAX) {
+		log_err("Unexpected MSS retrieved");
 		goto err;
 	}
 
@@ -163,13 +207,14 @@ int main(int argc, char **argv)
 	int server_v6 = -1;
 	int results = -1;
 	int err = 0;
+	bool xdp;
 
 	if (argc < 2) {
 		fprintf(stderr, "Usage: %s prog_id\n", argv[0]);
 		exit(1);
 	}
 
-	results = get_map_fd_by_prog_id(atoi(argv[1]));
+	results = get_map_fd_by_prog_id(atoi(argv[1]), &xdp);
 	if (results < 0) {
 		log_err("Can't get map");
 		goto err;
@@ -194,10 +239,10 @@ int main(int argc, char **argv)
 	if (server_v6 == -1)
 		goto err;
 
-	if (run_test(server, results))
+	if (run_test(server, results, xdp))
 		goto err;
 
-	if (run_test(server_v6, results))
+	if (run_test(server_v6, results, xdp))
 		goto err;
 
 	printf("ok\n");