[PATCH net v3 0/2] Fix PMTU for ESP-in-UDP encapsulation

@@ -645,10 +645,12 @@ static struct sock *__udp4_lib_err_encap(struct net *net,
 					 const struct iphdr *iph,
 					 struct udphdr *uh,
 					 struct udp_table *udptable,
+					 struct sock *sk,
 					 struct sk_buff *skb, u32 info)
 {
+	int (*lookup)(struct sock *sk, struct sk_buff *skb);
 	int network_offset, transport_offset;
-	struct sock *sk;
+	struct udp_sock *up;
 
 	network_offset = skb_network_offset(skb);
 	transport_offset = skb_transport_offset(skb);

@@ -659,18 +661,28 @@ static struct sock *__udp4_lib_err_encap(struct net *net,
 	/* Transport header needs to point to the UDP header */
 	skb_set_transport_header(skb, iph->ihl << 2);
 
+	if (sk) {
+		up = udp_sk(sk);
+
+		lookup = READ_ONCE(up->encap_err_lookup);
+		if (lookup && lookup(sk, skb))
+			sk = NULL;
+
+		goto out;
+	}
+
 	sk = __udp4_lib_lookup(net, iph->daddr, uh->source,
 			       iph->saddr, uh->dest, skb->dev->ifindex, 0,
 			       udptable, NULL);
 	if (sk) {
-		int (*lookup)(struct sock *sk, struct sk_buff *skb);
-		struct udp_sock *up = udp_sk(sk);
+		up = udp_sk(sk);
 
 		lookup = READ_ONCE(up->encap_err_lookup);
 		if (!lookup || lookup(sk, skb))
 			sk = NULL;
 	}
 
+out:
 	if (!sk)
 		sk = ERR_PTR(__udp4_lib_err_encap_no_sk(skb, info));
 

@@ -707,15 +719,16 @@ int __udp4_lib_err(struct sk_buff *skb, u32 info, struct udp_table *udptable)
 	sk = __udp4_lib_lookup(net, iph->daddr, uh->dest,
 			       iph->saddr, uh->source, skb->dev->ifindex,
 			       inet_sdif(skb), udptable, NULL);
+
 	if (!sk || udp_sk(sk)->encap_type) {
 		/* No socket for error: try tunnels before discarding */
-		sk = ERR_PTR(-ENOENT);
 		if (static_branch_unlikely(&udp_encap_needed_key)) {
-			sk = __udp4_lib_err_encap(net, iph, uh, udptable, skb,
+			sk = __udp4_lib_err_encap(net, iph, uh, udptable, sk, skb,
 						  info);
 			if (!sk)
 				return 0;
-		}
+		} else
+			sk = ERR_PTR(-ENOENT);
 
 		if (IS_ERR(sk)) {
 			__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);

@@ -502,12 +502,14 @@ static struct sock *__udp6_lib_err_encap(struct net *net,
 					 const struct ipv6hdr *hdr, int offset,
 					 struct udphdr *uh,
 					 struct udp_table *udptable,
+					 struct sock *sk,
 					 struct sk_buff *skb,
 					 struct inet6_skb_parm *opt,
 					 u8 type, u8 code, __be32 info)
 {
+	int (*lookup)(struct sock *sk, struct sk_buff *skb);
 	int network_offset, transport_offset;
-	struct sock *sk;
+	struct udp_sock *up;
 
 	network_offset = skb_network_offset(skb);
 	transport_offset = skb_transport_offset(skb);

@@ -518,18 +520,28 @@ static struct sock *__udp6_lib_err_encap(struct net *net,
 	/* Transport header needs to point to the UDP header */
 	skb_set_transport_header(skb, offset);
 
+	if (sk) {
+		up = udp_sk(sk);
+
+		lookup = READ_ONCE(up->encap_err_lookup);
+		if (lookup && lookup(sk, skb))
+			sk = NULL;
+
+		goto out;
+	}
+
 	sk = __udp6_lib_lookup(net, &hdr->daddr, uh->source,
 			       &hdr->saddr, uh->dest,
 			       inet6_iif(skb), 0, udptable, skb);
 	if (sk) {
-		int (*lookup)(struct sock *sk, struct sk_buff *skb);
-		struct udp_sock *up = udp_sk(sk);
+		up = udp_sk(sk);
 
 		lookup = READ_ONCE(up->encap_err_lookup);
 		if (!lookup || lookup(sk, skb))
 			sk = NULL;
 	}
 
+out:
 	if (!sk) {
 		sk = ERR_PTR(__udp6_lib_err_encap_no_sk(skb, opt, type, code,
 							offset, info));

@@ -558,16 +570,17 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 
 	sk = __udp6_lib_lookup(net, daddr, uh->dest, saddr, uh->source,
 			       inet6_iif(skb), inet6_sdif(skb), udptable, NULL);
+
 	if (!sk || udp_sk(sk)->encap_type) {
 		/* No socket for error: try tunnels before discarding */
-		sk = ERR_PTR(-ENOENT);
 		if (static_branch_unlikely(&udpv6_encap_needed_key)) {
 			sk = __udp6_lib_err_encap(net, hdr, offset, uh,
-						  udptable, skb,
+						  udptable, sk, skb,
 						  opt, type, code, info);
 			if (!sk)
 				return 0;
-		}
+		} else
+			sk = ERR_PTR(-ENOENT);
 
 		if (IS_ERR(sk)) {
 			__ICMP6_INC_STATS(net, __in6_dev_get(skb->dev),

@@ -11,9 +11,11 @@
 #include <sys/socket.h>
 #include <sys/wait.h>
 #include <linux/tcp.h>
+#include <linux/udp.h>
 #include <arpa/inet.h>
 #include <net/if.h>
 #include <netinet/in.h>
+#include <netinet/ip.h>
 #include <netdb.h>
 #include <fcntl.h>
 #include <libgen.h>

@@ -27,6 +29,10 @@
 #include <time.h>
 #include <errno.h>
 
+#include <linux/xfrm.h>
+#include <linux/ipsec.h>
+#include <linux/pfkeyv2.h>
+
 #ifndef IPV6_UNICAST_IF
 #define IPV6_UNICAST_IF         76
 #endif

@@ -114,6 +120,9 @@ struct sock_args {
 		struct in_addr  in;
 		struct in6_addr in6;
 	} expected_raddr;
+
+	/* ESP in UDP encap test */
+	int use_xfrm;
 };
 
 static int server_mode;

@@ -1346,6 +1355,41 @@ static int bind_socket(int sd, struct sock_args *args)
 	return 0;
 }
 
+static int config_xfrm_policy(int sd, struct sock_args *args)
+{
+	struct xfrm_userpolicy_info policy = {};
+	int type = UDP_ENCAP_ESPINUDP;
+	int xfrm_af = IP_XFRM_POLICY;
+	int level = SOL_IP;
+
+	if (args->type != SOCK_DGRAM) {
+		log_error("Invalid socket type. Only DGRAM could be used for XFRM\n");
+		return 1;
+	}
+
+	policy.action = XFRM_POLICY_ALLOW;
+	policy.sel.family = args->version;
+	if (args->version == AF_INET6) {
+		xfrm_af = IPV6_XFRM_POLICY;
+		level = SOL_IPV6;
+	}
+
+	policy.dir = XFRM_POLICY_OUT;
+	if (setsockopt(sd, level, xfrm_af, &policy, sizeof(policy)) < 0)
+		return 1;
+
+	policy.dir = XFRM_POLICY_IN;
+	if (setsockopt(sd, level, xfrm_af, &policy, sizeof(policy)) < 0)
+		return 1;
+
+	if (setsockopt(sd, IPPROTO_UDP, UDP_ENCAP, &type, sizeof(type)) < 0) {
+		log_err_errno("Failed to set xfrm encap");
+		return 1;
+	}
+
+	return 0;
+}
+
 static int lsock_init(struct sock_args *args)
 {
 	long flags;

@@ -1389,6 +1433,11 @@ static int lsock_init(struct sock_args *args)
 	if (fcntl(sd, F_SETFD, FD_CLOEXEC) < 0)
 		log_err_errno("Failed to set close-on-exec flag");
 
+	if (args->use_xfrm && config_xfrm_policy(sd, args)) {
+		log_err_errno("Failed to set xfrm policy");
+		goto err;
+	}
+
 out:
 	return sd;
 

@@ -1772,7 +1821,7 @@ static int ipc_parent(int cpid, int fd, struct sock_args *args)
 	return client_status;
 }
 
-#define GETOPT_STR  "sr:l:c:p:t:g:P:DRn:M:X:m:d:I:BN:O:SCi6L:0:1:2:3:Fbq"
+#define GETOPT_STR  "sr:l:c:p:t:g:P:DRn:M:X:m:d:I:BN:O:SCi6xL:0:1:2:3:Fbq"
 
 static void print_usage(char *prog)
 {

@@ -1795,6 +1844,7 @@ static void print_usage(char *prog)
 	"    -D|R          datagram (D) / raw (R) socket (default stream)\n"
 	"    -l addr       local address to bind to in server mode\n"
 	"    -c addr       local address to bind to in client mode\n"
+	"    -x            configure XFRM policy on socket\n"
 	"\n"
 	"    -d dev        bind socket to given device name\n"
 	"    -I dev        bind socket to given device name - server mode\n"

@@ -1966,6 +2016,9 @@ int main(int argc, char *argv[])
 		case 'q':
 			quiet = 1;
 			break;
+		case 'x':
+			args.use_xfrm = 1;
+			break;
 		default:
 			print_usage(argv[0]);
 			return 1;

@@ -118,6 +118,16 @@
 #	below for IPv6 doesn't apply here, because, on IPv4, administrative MTU
 #	changes alone won't affect PMTU
 #
+# - pmtu_vti4_udp_exception
+#       Same as pmtu_vti4_exception, but using ESP-in-UDP
+#
+# - pmtu_vti4_udp_routed_exception
+#       Set up vti tunnel on top of veth connected through routing namespace and
+#	add xfrm states and policies with ESP-in-UDP encapsulation. Check that
+#	route exception is not created if link layer MTU is not exceeded, then
+#	lower MTU on second part of routed environment and check that exception
+#	is created with the expected PMTU.
+#
 # - pmtu_vti6_exception
 #	Set up vti6 tunnel on top of veth, with xfrm states and policies, in two
 #	namespaces with matching endpoints. Check that route exception is

@@ -125,6 +135,13 @@
 #	decrease and increase MTU of tunnel, checking that route exception PMTU
 #	changes accordingly
 #
+# - pmtu_vti6_udp_exception
+#       Same as pmtu_vti6_exception, but using ESP-in-UDP
+#
+# - pmtu_vti6_udp_routed_exception
+#	Same as pmtu_vti6_udp_routed_exception but with routing between vti
+#	endpoints
+#
 # - pmtu_vti4_default_mtu
 #	Set up vti4 tunnel on top of veth, in two namespaces with matching
 #	endpoints. Check that MTU assigned to vti interface is the MTU of the

@@ -224,6 +241,10 @@ tests="
 	pmtu_ipv6_ipv6_exception	IPv6 over IPv6: PMTU exceptions		1
 	pmtu_vti6_exception		vti6: PMTU exceptions			0
 	pmtu_vti4_exception		vti4: PMTU exceptions			0
+	pmtu_vti6_udp_exception		vti6: PMTU exceptions (ESP-in-UDP)	0
+	pmtu_vti4_udp_exception		vti4: PMTU exceptions (ESP-in-UDP)	0
+	pmtu_vti6_udp_routed_exception	vti6: PMTU exceptions, routed (ESP-in-UDP)	0
+	pmtu_vti4_udp_routed_exception	vti4: PMTU exceptions, routed (ESP-in-UDP)	0
 	pmtu_vti4_default_mtu		vti4: default MTU assignment		0
 	pmtu_vti6_default_mtu		vti6: default MTU assignment		0
 	pmtu_vti4_link_add_mtu		vti4: MTU setting on link creation	0

@@ -246,7 +267,6 @@ ns_b="ip netns exec ${NS_B}"
 ns_c="ip netns exec ${NS_C}"
 ns_r1="ip netns exec ${NS_R1}"
 ns_r2="ip netns exec ${NS_R2}"
-
 # Addressing and routing for tests with routers: four network segments, with
 # index SEGMENT between 1 and 4, a common prefix (PREFIX4 or PREFIX6) and an
 # identifier ID, which is 1 for hosts (A and B), 2 for routers (R1 and R2).

@@ -279,7 +299,6 @@ routes="
 	A	${prefix6}:${b_r2}::1	${prefix6}:${a_r2}::2
 	B	default			${prefix6}:${b_r1}::2
 "
-
 USE_NH="no"
 #	ns	family	nh id	   destination		gateway
 nexthops="

@@ -326,6 +345,7 @@ dummy6_mask="64"
 
 err_buf=
 tcpdump_pids=
+nettest_pids=
 
 err() {
 	err_buf="${err_buf}${1}

@@ -548,6 +568,14 @@ setup_vti6() {
 	setup_vti 6 ${veth6_a_addr} ${veth6_b_addr} ${tunnel6_a_addr} ${tunnel6_b_addr} ${tunnel6_mask}
 }
 
+setup_vti4routed() {
+	setup_vti 4 ${prefix4}.${a_r1}.1 ${prefix4}.${b_r1}.1 ${tunnel4_a_addr} ${tunnel4_b_addr} ${tunnel4_mask}
+}
+
+setup_vti6routed() {
+	setup_vti 6 ${prefix6}:${a_r1}::1 ${prefix6}:${b_r1}::1 ${tunnel6_a_addr} ${tunnel6_b_addr} ${tunnel6_mask}
+}
+
 setup_vxlan_or_geneve() {
 	type="${1}"
 	a_addr="${2}"

@@ -619,18 +647,36 @@ setup_xfrm() {
 	proto=${1}
 	veth_a_addr="${2}"
 	veth_b_addr="${3}"
+	encap=${4}
 
-	run_cmd ${ns_a} ip -${proto} xfrm state add src ${veth_a_addr} dst ${veth_b_addr} spi 0x1000 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel || return 1
-	run_cmd ${ns_a} ip -${proto} xfrm state add src ${veth_b_addr} dst ${veth_a_addr} spi 0x1001 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
+	run_cmd ${ns_a} ip -${proto} xfrm state add src ${veth_a_addr} dst ${veth_b_addr} spi 0x1000 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel ${encap} || return 1
+	run_cmd ${ns_a} ip -${proto} xfrm state add src ${veth_b_addr} dst ${veth_a_addr} spi 0x1001 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel ${encap}
 	run_cmd ${ns_a} ip -${proto} xfrm policy add dir out mark 10 tmpl src ${veth_a_addr} dst ${veth_b_addr} proto esp mode tunnel
 	run_cmd ${ns_a} ip -${proto} xfrm policy add dir in mark 10 tmpl src ${veth_b_addr} dst ${veth_a_addr} proto esp mode tunnel
 
-	run_cmd ${ns_b} ip -${proto} xfrm state add src ${veth_a_addr} dst ${veth_b_addr} spi 0x1000 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
-	run_cmd ${ns_b} ip -${proto} xfrm state add src ${veth_b_addr} dst ${veth_a_addr} spi 0x1001 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel
+	run_cmd ${ns_b} ip -${proto} xfrm state add src ${veth_a_addr} dst ${veth_b_addr} spi 0x1000 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel ${encap}
+	run_cmd ${ns_b} ip -${proto} xfrm state add src ${veth_b_addr} dst ${veth_a_addr} spi 0x1001 proto esp aead 'rfc4106(gcm(aes))' 0x0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f0f 128 mode tunnel ${encap}
 	run_cmd ${ns_b} ip -${proto} xfrm policy add dir out mark 10 tmpl src ${veth_b_addr} dst ${veth_a_addr} proto esp mode tunnel
 	run_cmd ${ns_b} ip -${proto} xfrm policy add dir in mark 10 tmpl src ${veth_a_addr} dst ${veth_b_addr} proto esp mode tunnel
 }
 
+setup_nettest_xfrm() {
+	which nettest >/dev/null
+	if [ $? -ne 0 ]; then
+        	echo "'nettest' command not found; skipping tests"
+	        return 1
+	fi
+
+	[ ${1} -eq 6 ] && proto="-6" || proto=""
+	port=${2}
+
+	run_cmd ${ns_a} nettest ${proto} -q -D -s -x -p ${port} -t 5 &
+	nettest_pids="${nettest_pids} $!"
+
+	run_cmd ${ns_b} nettest ${proto} -q -D -s -x -p ${port} -t 5 &
+	nettest_pids="${nettest_pids} $!"
+}
+
 setup_xfrm4() {
 	setup_xfrm 4 ${veth4_a_addr} ${veth4_b_addr}
 }

@@ -639,6 +685,26 @@ setup_xfrm6() {
 	setup_xfrm 6 ${veth6_a_addr} ${veth6_b_addr}
 }
 
+setup_xfrm4udp() {
+	setup_xfrm 4 ${veth4_a_addr} ${veth4_b_addr} "encap espinudp 4500 4500 0.0.0.0"
+	setup_nettest_xfrm 4 4500
+}
+
+setup_xfrm6udp() {
+	setup_xfrm 6 ${veth6_a_addr} ${veth6_b_addr} "encap espinudp 4500 4500 0.0.0.0"
+	setup_nettest_xfrm 6 4500
+}
+
+setup_xfrm4udprouted() {
+	setup_xfrm 4 ${prefix4}.${a_r1}.1 ${prefix4}.${b_r1}.1 "encap espinudp 4500 4500 0.0.0.0"
+	setup_nettest_xfrm 4 4500
+}
+
+setup_xfrm6udprouted() {
+	setup_xfrm 6 ${prefix6}:${a_r1}::1 ${prefix6}:${b_r1}::1 "encap espinudp 4500 4500 0.0.0.0"
+	setup_nettest_xfrm 6 4500
+}
+
 setup_routing_old() {
 	for i in ${routes}; do
 		[ "${ns}" = "" ]	&& ns="${i}"		&& continue

@@ -823,6 +889,11 @@ cleanup() {
 	done
 	tcpdump_pids=
 
+	for pid in ${nettest_pids}; do
+		kill ${pid}
+	done
+	nettest_pids=
+
 	for n in ${NS_A} ${NS_B} ${NS_C} ${NS_R1} ${NS_R2}; do
 		ip netns del ${n} 2> /dev/null
 	done

@@ -1432,6 +1503,135 @@ test_pmtu_vti6_exception() {
 	return ${fail}
 }
 
+test_pmtu_vti4_udp_exception() {
+	setup namespaces veth vti4 xfrm4udp || return $ksft_skip
+	trace "${ns_a}" veth_a    "${ns_b}" veth_b \
+	      "${ns_a}" vti4_a    "${ns_b}" vti4_b
+
+	veth_mtu=1500
+	vti_mtu=$((veth_mtu - 20))
+
+	#                                UDP   SPI   SN   IV  ICV   pad length   next header
+	esp_payload_rfc4106=$((vti_mtu - 8   - 4   - 4  - 8 - 16  - 1          - 1))
+	ping_payload=$((esp_payload_rfc4106 - 28))
+
+	mtu "${ns_a}" veth_a ${veth_mtu}
+	mtu "${ns_b}" veth_b ${veth_mtu}
+	mtu "${ns_a}" vti4_a ${vti_mtu}
+	mtu "${ns_b}" vti4_b ${vti_mtu}
+
+	# Send DF packet without exceeding link layer MTU, check that no
+	# exception is created
+	run_cmd ${ns_a} ping -q -M want -i 0.1 -w 1 -s ${ping_payload} ${tunnel4_b_addr}
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel4_b_addr})"
+	check_pmtu_value "" "${pmtu}" "sending packet smaller than PMTU (IP payload length ${esp_payload_rfc4106})" || return 1
+
+	# Now exceed link layer MTU by one byte, check that exception is created
+	# with the right PMTU value
+	run_cmd ${ns_a} ping -q -M want -i 0.1 -w 1 -s $((ping_payload + 1)) ${tunnel4_b_addr}
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel4_b_addr})"
+	check_pmtu_value "${esp_payload_rfc4106}" "${pmtu}" "exceeding PMTU (IP payload length $((esp_payload_rfc4106 + 1)))"
+}
+
+test_pmtu_vti6_udp_exception() {
+	setup namespaces veth vti6 xfrm6udp || return $ksft_skip
+	trace "${ns_a}" veth_a    "${ns_b}" veth_b \
+	      "${ns_a}" vti6_a    "${ns_b}" vti6_b
+	fail=0
+
+	# Create route exception by exceeding link layer MTU
+	mtu "${ns_a}" veth_a 4000
+	mtu "${ns_b}" veth_b 4000
+	mtu "${ns_a}" vti6_a 5000
+	mtu "${ns_b}" vti6_b 5000
+	run_cmd ${ns_a} ${ping6} -q -i 0.1 -w 1 -s 60000 ${tunnel6_b_addr}
+
+	# Check that exception was created
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel6_b_addr})"
+	check_pmtu_value any "${pmtu}" "creating tunnel exceeding link layer MTU" || return 1
+
+	# Decrease tunnel MTU, check for PMTU decrease in route exception
+	mtu "${ns_a}" vti6_a 3000
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel6_b_addr})"
+	check_pmtu_value "3000" "${pmtu}" "decreasing tunnel MTU" || fail=1
+
+	# Increase tunnel MTU, check for PMTU increase in route exception
+	mtu "${ns_a}" vti6_a 9000
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel6_b_addr})"
+	check_pmtu_value "9000" "${pmtu}" "increasing tunnel MTU" || fail=1
+
+	return ${fail}
+}
+
+test_pmtu_vti4_udp_routed_exception() {
+	setup namespaces routing vti4routed xfrm4udprouted || return $ksft_skip
+	trace "${ns_a}" veth_A-R1    "${ns_b}" veth_B-R1 \
+	      "${ns_a}" vti4_a       "${ns_b}" vti4_b
+
+	veth_mtu=1500
+	vti_mtu=$((veth_mtu - 20))
+
+	#                                UDP   SPI   SN   IV  ICV   pad length   next header
+	esp_payload_rfc4106=$((vti_mtu - 8   - 4   - 4  - 8 - 16  - 1          - 1))
+	ping_payload=$((esp_payload_rfc4106 - 28))
+
+        mtu "${ns_a}"  veth_A-R1 ${veth_mtu}
+        mtu "${ns_r1}" veth_R1-A ${veth_mtu}
+        mtu "${ns_b}"  veth_B-R1 ${veth_mtu}
+        mtu "${ns_r1}" veth_R1-B ${veth_mtu}
+
+	mtu "${ns_a}" vti4_a ${vti_mtu}
+	mtu "${ns_b}" vti4_b ${vti_mtu}
+
+	# Send DF packet without exceeding link layer MTU, check that no
+	# exception is created
+	run_cmd ${ns_a} ping -q -M want -i 0.1 -w 1 -s ${ping_payload} ${tunnel4_b_addr}
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel4_b_addr})"
+	check_pmtu_value "" "${pmtu}" "sending packet smaller than PMTU (IP payload length ${esp_payload_rfc4106})" || return 1
+
+	# Now decrease link layer MTU by 8 bytes on R1, check that exception is created
+	# with the right PMTU value
+        mtu "${ns_r1}" veth_R1-B $((veth_mtu - 8))
+	run_cmd ${ns_a} ping -q -M want -i 0.1 -w 1 -s $((ping_payload)) ${tunnel4_b_addr}
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel4_b_addr})"
+	check_pmtu_value "$((esp_payload_rfc4106 - 8))" "${pmtu}" "exceeding PMTU (IP payload length $((esp_payload_rfc4106)))"
+}
+
+test_pmtu_vti6_udp_routed_exception() {
+	setup namespaces routing vti6routed xfrm6udprouted || return $ksft_skip
+	trace "${ns_a}" veth_A-R1    "${ns_b}" veth_B-R1 \
+	      "${ns_a}" vti6_a       "${ns_b}" vti6_b
+
+	veth_mtu=1500
+	vti_mtu=$((veth_mtu - 40))
+
+	#                                UDP   SPI   SN   IV  ICV   pad length   next header
+	esp_payload_rfc4106=$((vti_mtu - 8   - 4   - 4  - 8 - 16  - 1          - 1))
+	ping_payload=$((esp_payload_rfc4106 - 48))
+
+        mtu "${ns_a}"  veth_A-R1 ${veth_mtu}
+        mtu "${ns_r1}" veth_R1-A ${veth_mtu}
+        mtu "${ns_b}"  veth_B-R1 ${veth_mtu}
+        mtu "${ns_r1}" veth_R1-B ${veth_mtu}
+
+	# mtu "${ns_a}" vti6_a ${vti_mtu}
+	# mtu "${ns_b}" vti6_b ${vti_mtu}
+
+	run_cmd ${ns_a} ${ping6} -q -M want -i 0.1 -w 1 -s ${ping_payload} ${tunnel6_b_addr}
+
+	# Check that exception was not created
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel6_b_addr})"
+	check_pmtu_value "" "${pmtu}" "sending packet smaller than PMTU (IP payload length ${esp_payload_rfc4106})" || return 1
+
+	# Now decrease link layer MTU by 8 bytes on R1, check that exception is created
+	# with the right PMTU value
+        mtu "${ns_r1}" veth_R1-B $((veth_mtu - 8))
+	run_cmd ${ns_a} ${ping6} -q -M want -i 0.1 -w 1 -s $((ping_payload)) ${tunnel6_b_addr}
+	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${tunnel6_b_addr})"
+	check_pmtu_value "$((esp_payload_rfc4106 - 8))" "${pmtu}" "exceeding PMTU (IP payload length $((esp_payload_rfc4106)))"
+
+}
+
 test_pmtu_vti4_default_mtu() {
 	setup namespaces veth vti4 || return $ksft_skip