[PATCH 3/7] nat: Split notion of gateway/router from from guest-visible host address

[David Gibson <david@gibson.dropbear.id.au>]

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The @gw fields in the ip4_ctx and ip6_ctx give the (host's) default
route gateway.  We use this for two quite distinct things: actually
advertising the correct gateway to the guest/ns (e.g. in DHCP and NDP)
and for a limited form of NAT.  So that the guest can access services
on the host, we map the gateway address within the guest to the
loopback address on the host.

Using the gateway address for this isn't necessarily the best choice
for this purpose, certainly not for all circumstances.  So, start off
by splitting the notion of these into two different values: @router
which is the actual router address and @nattohost which is the guest
visible address to remap to the host's loopback.

For now they always have the same value, but we can change that in future.

Similarly, we make changes to the tests so they no longer assume that
the gateway and nat-to-host address are the same.  Rather than using
__GW__ throughout, use __NAT_TO_{HOST,NS}[46]__ variables which are
provided by the setup functions.  For now those are always set to the
gateway address, but that can change in future.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 conf.c                | 46 +++++++++++++++++++++++--------------------
 dhcp.c                | 14 ++++++-------
 dhcpv6.c              |  4 ++--
 ndp.c                 |  4 ++--
 passt.h               | 12 +++++++----
 pasta.c               |  4 ++--
 tcp.c                 | 10 +++++-----
 test/lib/setup        | 12 +++++++++++
 test/lib/test         | 12 +++++++++++
 test/passt/dhcp       |  7 +++++--
 test/passt/tcp        | 10 ++++------
 test/passt/udp        |  5 ++---
 test/passt_in_ns/tcp  | 28 +++++++++++---------------
 test/passt_in_ns/udp  | 14 ++++++-------
 test/pasta/tcp        | 11 ++++-------
 test/pasta/udp        |  6 ++----
 test/perf/passt_tcp   | 30 +++++++++++++---------------
 test/perf/passt_udp   | 26 +++++++++++-------------
 test/perf/pasta_tcp   | 26 +++++++++++-------------
 test/perf/pasta_udp   | 22 ++++++++++-----------
 test/two_guests/basic | 10 ++++------
 udp.c                 | 10 +++++-----
 22 files changed, 167 insertions(+), 156 deletions(-)

diff --git a/conf.c b/conf.c
index 447b000..bfc825b 100644
--- a/conf.c
+++ b/conf.c
@@ -419,11 +419,11 @@ static void add_dns4(struct ctx *c, struct in_addr *addr, struct in_addr **conf)
 	/* Guest or container can only access local addresses via redirect */
 	if (IN4_IS_ADDR_LOOPBACK(addr)) {
 		if (!c->no_map_gw) {
-			**conf = c->ip4.gw;
+			**conf = c->ip4.nattohost;
 			(*conf)++;
 
 			if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_match))
-				c->ip4.dns_match = c->ip4.gw;
+				c->ip4.dns_match = c->ip4.nattohost;
 		}
 	} else {
 		**conf = *addr;
@@ -446,7 +446,7 @@ static void add_dns6(struct ctx *c,
 	/* Guest or container can only access local addresses via redirect */
 	if (IN6_IS_ADDR_LOOPBACK(addr)) {
 		if (!c->no_map_gw) {
-			memcpy(*conf, &c->ip6.gw, sizeof(**conf));
+			memcpy(*conf, &c->ip6.nattohost, sizeof(**conf));
 			(*conf)++;
 
 			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_match))
@@ -645,14 +645,14 @@ static unsigned int conf_ip4(unsigned int ifi,
 		return 0;
 	}
 
-	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->gw))
-		nl_route(0, ifi, AF_INET, &ip4->gw);
+	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->router))
+		nl_route(0, ifi, AF_INET, &ip4->router);
 
 	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->addr))
 		nl_addr(0, ifi, AF_INET, &ip4->addr, &ip4->prefix_len, NULL);
 
 	addr = ntohl(ip4->addr.s_addr);
-	gw = ntohl(ip4->gw.s_addr);
+	gw = ntohl(ip4->router.s_addr);
 
 	if (!ip4->prefix_len) {
 		if (IN_CLASSA(addr))
@@ -688,7 +688,9 @@ static unsigned int conf_ip4(unsigned int ifi,
 	if (MAC_IS_ZERO(mac))
 		nl_link(0, ifi, mac, 0, 0);
 
-	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->gw) ||
+	ip4->nattohost = ip4->router;
+
+	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->router) ||
 	    IN4_IS_ADDR_UNSPECIFIED(&ip4->addr) ||
 	    MAC_IS_ZERO(mac))
 		return 0;
@@ -717,8 +719,8 @@ static unsigned int conf_ip6(unsigned int ifi,
 		return 0;
 	}
 
-	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->gw))
-		nl_route(0, ifi, AF_INET6, &ip6->gw);
+	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->router))
+		nl_route(0, ifi, AF_INET6, &ip6->router);
 
 	nl_addr(0, ifi, AF_INET6,
 		IN6_IS_ADDR_UNSPECIFIED(&ip6->addr) ? &ip6->addr : NULL,
@@ -730,7 +732,9 @@ static unsigned int conf_ip6(unsigned int ifi,
 	if (MAC_IS_ZERO(mac))
 		nl_link(0, ifi, mac, 0, 0);
 
-	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->gw) ||
+	ip6->nattohost = ip6->router;
+
+	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->router) ||
 	    IN6_IS_ADDR_UNSPECIFIED(&ip6->addr) ||
 	    IN6_IS_ADDR_UNSPECIFIED(&ip6->addr_ll) ||
 	    MAC_IS_ZERO(mac))
@@ -984,7 +988,7 @@ static void conf_print(const struct ctx *c)
 			info("    mask: %s",
 			     inet_ntop(AF_INET, &mask,        buf4, sizeof(buf4)));
 			info("    router: %s",
-			     inet_ntop(AF_INET, &c->ip4.gw,   buf4, sizeof(buf4)));
+			     inet_ntop(AF_INET, &c->ip4.router, buf4, sizeof(buf4)));
 		}
 
 		for (i = 0; !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns[i]); i++) {
@@ -1014,7 +1018,7 @@ static void conf_print(const struct ctx *c)
 		info("    assign: %s",
 		     inet_ntop(AF_INET6, &c->ip6.addr, buf6, sizeof(buf6)));
 		info("    router: %s",
-		     inet_ntop(AF_INET6, &c->ip6.gw,   buf6, sizeof(buf6)));
+		     inet_ntop(AF_INET6, &c->ip6.router, buf6, sizeof(buf6)));
 		info("    our link-local: %s",
 		     inet_ntop(AF_INET6, &c->ip6.addr_ll, buf6, sizeof(buf6)));
 
@@ -1518,17 +1522,17 @@ void conf(struct ctx *c, int argc, char **argv)
 			}
 			break;
 		case 'g':
-			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.gw)		&&
-			    inet_pton(AF_INET6, optarg, &c->ip6.gw)	&&
-			    !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.gw)	&&
-			    !IN6_IS_ADDR_LOOPBACK(&c->ip6.gw))
+			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.router)	&&
+			    inet_pton(AF_INET6, optarg, &c->ip6.router)	&&
+			    !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.router)	&&
+			    !IN6_IS_ADDR_LOOPBACK(&c->ip6.router))
 				break;
 
-			if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.gw)		&&
-			    inet_pton(AF_INET, optarg, &c->ip4.gw)	&&
-			    !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.gw)	&&
-			    !IN4_IS_ADDR_BROADCAST(&c->ip4.gw)		&&
-			    !IN4_IS_ADDR_LOOPBACK(&c->ip4.gw))
+			if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.router)	&&
+			    inet_pton(AF_INET, optarg, &c->ip4.router)	&&
+			    !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.router)	&&
+			    !IN4_IS_ADDR_BROADCAST(&c->ip4.router)	&&
+			    !IN4_IS_ADDR_LOOPBACK(&c->ip4.router))
 				break;
 
 			die("Invalid gateway address: %s", optarg);
diff --git a/dhcp.c b/dhcp.c
index d04648c..1910c0c 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -336,20 +336,20 @@ int dhcp(const struct ctx *c, const struct pool *p)
 
 	m->yiaddr = c->ip4.addr;
 	mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len));
-	memcpy(opts[1].s,  &mask,        sizeof(mask));
-	memcpy(opts[3].s,  &c->ip4.gw,   sizeof(c->ip4.gw));
-	memcpy(opts[54].s, &c->ip4.gw,   sizeof(c->ip4.gw));
+	memcpy(opts[1].s,  &mask,          sizeof(mask));
+	memcpy(opts[3].s,  &c->ip4.router, sizeof(c->ip4.router));
+	memcpy(opts[54].s, &c->ip4.router, sizeof(c->ip4.router));
 
 	/* If the gateway is not on the assigned subnet, send an option 121
 	 * (Classless Static Routing) adding a dummy route to it.
 	 */
 	if ((c->ip4.addr.s_addr & mask.s_addr)
-	    != (c->ip4.gw.s_addr & mask.s_addr)) {
+	    != (c->ip4.router.s_addr & mask.s_addr)) {
 		/* a.b.c.d/32:0.0.0.0, 0:a.b.c.d */
 		opts[121].slen = 14;
 		opts[121].s[0] = 32;
-		memcpy(opts[121].s + 1,  &c->ip4.gw, sizeof(c->ip4.gw));
-		memcpy(opts[121].s + 10, &c->ip4.gw, sizeof(c->ip4.gw));
+		memcpy(opts[121].s + 1,  &c->ip4.router, sizeof(c->ip4.router));
+		memcpy(opts[121].s + 10, &c->ip4.router, sizeof(c->ip4.router));
 	}
 
 	if (c->mtu != -1) {
@@ -368,7 +368,7 @@ int dhcp(const struct ctx *c, const struct pool *p)
 		opt_set_dns_search(c, sizeof(m->o));
 
 	len = offsetof(struct msg, o) + fill(m);
-	tap_udp4_send(c, c->ip4.gw, 67, c->ip4.addr, 68, m, len);
+	tap_udp4_send(c, c->ip4.router, 67, c->ip4.addr, 68, m, len);
 
 	return 1;
 }
diff --git a/dhcpv6.c b/dhcpv6.c
index fc42a84..84e6ff1 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -440,8 +440,8 @@ int dhcpv6(struct ctx *c, const struct pool *p,
 
 	c->ip6.addr_ll_seen = *saddr;
 
-	if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
-		src = &c->ip6.gw;
+	if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.router))
+		src = &c->ip6.router;
 	else
 		src = &c->ip6.addr_ll;
 
diff --git a/ndp.c b/ndp.c
index adab1d2..febb1da 100644
--- a/ndp.c
+++ b/ndp.c
@@ -181,8 +181,8 @@ dns_done:
 	else
 		c->ip6.addr_seen = *saddr;
 
-	if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
-		rsaddr = &c->ip6.gw;
+	if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.router))
+		rsaddr = &c->ip6.router;
 	else
 		rsaddr = &c->ip6.addr_ll;
 
diff --git a/passt.h b/passt.h
index 73fe808..e308fe1 100644
--- a/passt.h
+++ b/passt.h
@@ -102,7 +102,8 @@ enum passt_modes {
  * @addr:		IPv4 address for external, routable interface
  * @addr_seen:		Latest IPv4 address seen as source from tap
  * @prefixlen:		IPv4 prefix length (netmask)
- * @gw:			Default IPv4 gateway, network order
+ * @router:		Default IPv4 router, network order
+ * @nattohost:		NAT this address from guest to host's 127.0.0.1
  * @dns:		DNS addresses for DHCP, zero-terminated, network order
  * @dns_match:		Forward DNS query if sent to this address, network order
  * @dns_host:		Use this DNS on the host for forwarding, network order
@@ -113,7 +114,8 @@ struct ip4_ctx {
 	struct in_addr addr;
 	struct in_addr addr_seen;
 	int prefix_len;
-	struct in_addr gw;
+	struct in_addr router;
+	struct in_addr nattohost;
 	struct in_addr dns[MAXNS + 1];
 	struct in_addr dns_match;
 	struct in_addr dns_host;
@@ -128,7 +130,8 @@ struct ip4_ctx {
  * @addr_ll:		Link-local IPv6 address on external, routable interface
  * @addr_seen:		Latest IPv6 global/site address seen as source from tap
  * @addr_ll_seen:	Latest IPv6 link-local address seen as source from tap
- * @gw:			Default IPv6 gateway
+ * @router:		Default IPv6 router
+ * @nattohost:		NAT this address from guest to host's ::1
  * @dns:		DNS addresses for DHCPv6 and NDP, zero-terminated
  * @dns_match:		Forward DNS query if sent to this address
  * @dns_host:		Use this DNS on the host for forwarding
@@ -140,7 +143,8 @@ struct ip6_ctx {
 	struct in6_addr addr_ll;
 	struct in6_addr addr_seen;
 	struct in6_addr addr_ll_seen;
-	struct in6_addr gw;
+	struct in6_addr router;
+	struct in6_addr nattohost;
 	struct in6_addr dns[MAXNS + 1];
 	struct in6_addr dns_match;
 	struct in6_addr dns_host;
diff --git a/pasta.c b/pasta.c
index 3a4d704..c706cb1 100644
--- a/pasta.c
+++ b/pasta.c
@@ -268,14 +268,14 @@ void pasta_ns_conf(struct ctx *c)
 		if (c->ifi4) {
 			nl_addr(1, c->pasta_ifi, AF_INET, &c->ip4.addr,
 				&c->ip4.prefix_len, NULL);
-			nl_route(1, c->pasta_ifi, AF_INET, &c->ip4.gw);
+			nl_route(1, c->pasta_ifi, AF_INET, &c->ip4.router);
 		}
 
 		if (c->ifi6) {
 			int prefix_len = 64;
 			nl_addr(1, c->pasta_ifi, AF_INET6, &c->ip6.addr,
 				&prefix_len, NULL);
-			nl_route(1, c->pasta_ifi, AF_INET6, &c->ip6.gw);
+			nl_route(1, c->pasta_ifi, AF_INET6, &c->ip6.router);
 		}
 	} else {
 		nl_link(1, c->pasta_ifi, c->mac_guest, 0, 0);
diff --git a/tcp.c b/tcp.c
index 0ed9bfa..b0dacab 100644
--- a/tcp.c
+++ b/tcp.c
@@ -2041,9 +2041,9 @@ static void tcp_conn_from_tap(struct ctx *c, int af, const void *addr,
 			return;
 
 	if (!c->no_map_gw) {
-		if (af == AF_INET && IN4_ARE_ADDR_EQUAL(addr, &c->ip4.gw))
+		if (af == AF_INET && IN4_ARE_ADDR_EQUAL(addr, &c->ip4.nattohost))
 			addr4.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
-		if (af == AF_INET6 && IN6_ARE_ADDR_EQUAL(addr, &c->ip6.gw))
+		if (af == AF_INET6 && IN6_ARE_ADDR_EQUAL(addr, &c->ip6.nattohost))
 			addr6.sin6_addr	= in6addr_loopback;
 	}
 
@@ -2713,15 +2713,15 @@ static void tcp_snat_inbound(const struct ctx *c, union inany_addr *addr)
 		if (IN4_IS_ADDR_LOOPBACK(addr4) ||
 		    IN4_IS_ADDR_UNSPECIFIED(addr4) ||
 		    IN4_ARE_ADDR_EQUAL(addr4, &c->ip4.addr_seen))
-			*addr4 = c->ip4.gw;
+			*addr4 = c->ip4.nattohost;
 	} else {
 		struct in6_addr *addr6 = &addr->a6;
 
 		if (IN6_IS_ADDR_LOOPBACK(addr6) ||
 		    IN6_ARE_ADDR_EQUAL(addr6, &c->ip6.addr_seen) ||
 		    IN6_ARE_ADDR_EQUAL(addr6, &c->ip6.addr)) {
-			if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
-				*addr6 = c->ip6.gw;
+			if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.nattohost))
+				*addr6 = c->ip6.nattohost;
 			else
 				*addr6 = c->ip6.addr_ll;
 		}
diff --git a/test/lib/setup b/test/lib/setup
index 9b39b9f..d85002e 100755
--- a/test/lib/setup
+++ b/test/lib/setup
@@ -40,6 +40,9 @@ setup_passt() {
 	#  10001     as server  |  forwarded to guest
 	#  10003                |      as server
 
+        __nat_to_host4="$(ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway')"
+        __nat_to_host6="$(ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway')"
+
 	__opts=
 	[ ${PCAP} -eq 1 ] && __opts="${__opts} -p ${LOGDIR}/passt.pcap"
 	[ ${DEBUG} -eq 1 ] && __opts="${__opts} -d"
@@ -87,6 +90,9 @@ setup_pasta() {
 	#  10002      as server     |    spliced to ns
 	#  10003   spliced to init  |      as server
 
+        __nat_to_host4="$(ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway')"
+        __nat_to_host6="$(ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway')"
+
 	__opts=
 	[ ${PCAP} -eq 1 ] && __opts="${__opts} -p ${LOGDIR}/pasta.pcap"
 	[ ${DEBUG} -eq 1 ] && __opts="${__opts} -d"
@@ -118,6 +124,10 @@ setup_passt_in_ns() {
 	#
 	#  10021    as server  | forwarded to guest |
 	#  10031    as server  | forwarded to guest |
+        __nat_to_host4="$(ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway')"
+        __nat_to_host6="$(ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway')"
+        __nat_to_ns4="${__nat_to_host4}"
+        __nat_to_ns6="${__nat_to_host6}"
 
 	__opts=
 	[ ${PCAP} -eq 1 ] && __opts="${__opts} -p ${LOGDIR}/pasta_with_passt.pcap"
@@ -181,6 +191,8 @@ setup_two_guests() {
 	#  10003            |           |  to init  |  to init   |  as server
 	#  10004            | as server |  to init  |  to guest  |  to ns #2
 	#  10005            |           |           |  as server |  to ns #2
+        __nat_to_host4="$(ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway')"
+        __nat_to_host6="$(ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway')"
 
 	__opts=
 	[ ${PCAP} -eq 1 ] && __opts="${__opts} -p ${LOGDIR}/pasta_1.pcap"
diff --git a/test/lib/test b/test/lib/test
index 115dd21..f4c4c43 100755
--- a/test/lib/test
+++ b/test/lib/test
@@ -356,6 +356,18 @@ test_one() {
 	STATEDIR="${STATEBASE}/${1}"
 	mkdir -p "${STATEDIR}"
 	TEST_ONE_subs="$(list_add_pair "${TEST_ONE_subs}" "__STATEDIR__" "${STATEDIR}")"
+        if [ -n "${__nat_to_host4}" ]; then
+                TEST_ONE_subs="$(list_add_pair "${TEST_ONE_subs}" "__NAT_TO_HOST4__" "${__nat_to_host4}")"
+        fi
+        if [ -n "${__nat_to_host6}" ]; then
+                TEST_ONE_subs="$(list_add_pair "${TEST_ONE_subs}" "__NAT_TO_HOST6__" "${__nat_to_host6}")"
+        fi
+        if [ -n "${__nat_to_ns4}" ]; then
+                TEST_ONE_subs="$(list_add_pair "${TEST_ONE_subs}" "__NAT_TO_NS4__" "${__nat_to_ns4}")"
+        fi
+        if [ -n "${__nat_to_ns6}" ]; then
+                TEST_ONE_subs="$(list_add_pair "${TEST_ONE_subs}" "__NAT_TO_NS6__" "${__nat_to_ns6}")"
+        fi
 	TEST_ONE_nok=-1
 	TEST_ONE_perf_nok=0
 	TEST_ONE_skip=0
diff --git a/test/passt/dhcp b/test/passt/dhcp
index 7272755..be6ab02 100644
--- a/test/passt/dhcp
+++ b/test/passt/dhcp
@@ -14,6 +14,9 @@
 gtools	ip jq dhclient sed tr
 htools	ip jq sed tr head
 
+test	Provided addresses
+gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
+
 test	Interface name
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 hout	HOST_IFNAME ip -j -4 route show|jq -rM '[.[] | select(.dst == "default").dev] | .[0]'
@@ -38,7 +41,7 @@ check	[ __MTU__ = 65520 ]
 test	DHCP: DNS
 gout	DNS sed -n 's/^nameserver \([0-9]*\.\)\(.*\)/\1\2/p' /etc/resolv.conf | tr '\n' ',' | sed 's/,$//;s/$/\n/'
 hout	HOST_DNS sed -n 's/^nameserver \([0-9]*\.\)\(.*\)/\1\2/p' /etc/resolv.conf | head -n3 | tr '\n' ',' | sed 's/,$//;s/$/\n/'
-check	[ "__DNS__" = "__HOST_DNS__" ] || [ "__DNS__" = "__HOST_GW__" -a "__HOST_DNS__" = "127.0.0.1" ]
+check	[ "__DNS__" = "__HOST_DNS__" ] || [ "__DNS__" = "__NAT_TO_HOST4__" -a "__HOST_DNS__" = "127.0.0.1" ]
 
 # FQDNs should be terminated by dots, but the guest DHCP client might omit them:
 # strip them first
@@ -62,7 +65,7 @@ check	[ "__GW6__" = "__HOST_GW6__" ]
 test	DHCPv6: DNS
 gout	DNS6 sed -n 's/^nameserver \([^:]*:\)\([^%]*\).*/\1\2/p' /etc/resolv.conf | tr '\n' ',' | sed 's/,$//;s/$/\n/'
 hout	HOST_DNS6 sed -n 's/^nameserver \([^:]*:\)\([^%]*\).*/\1\2/p' /etc/resolv.conf | tr '\n' ',' | sed 's/,$//;s/$/\n/'
-check	[ "__DNS6__" = "__HOST_DNS6__" ] || [ "__DNS6__" = "__HOST_GW6__" -a "__HOST_DNS6__" = "::1" ]
+check	[ "__DNS6__" = "__HOST_DNS6__" ] || [ "__DNS6__" = "__NAT_TO_HOST6__" -a "__HOST_DNS6__" = "::1" ]
 
 test	DHCPv6: search list
 gout	SEARCH6 sed 's/\. / /g' /etc/resolv.conf | sed 's/\.$//g' | sed -n 's/^search \(.*\)/\1/p' | tr ' \n' ',' | sed 's/,$//;s/$/\n/'
diff --git a/test/passt/tcp b/test/passt/tcp
index 91e49e0..cc8d1cf 100644
--- a/test/passt/tcp
+++ b/test/passt/tcp
@@ -26,8 +26,7 @@ guest	cmp /root/big.bin test_big.bin
 
 test	TCP/IPv4: guest to host: big transfer
 hostb	socat -u TCP4-LISTEN:10003,bind=127.0.0.1,reuseaddr OPEN:__TEMP_BIG__,create,trunc
-gout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-guest	socat -u OPEN:/root/big.bin TCP4:__GW__:10003
+guest	socat -u OPEN:/root/big.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __BASEPATH__/big.bin __TEMP_BIG__
 
@@ -41,7 +40,7 @@ guest	cmp /root/small.bin test_small.bin
 test	TCP/IPv4: guest to host: small transfer
 hostb	socat -u TCP4-LISTEN:10003,bind=127.0.0.1,reuseaddr OPEN:__TEMP_SMALL__,create,trunc
 sleep	1
-guest	socat -u OPEN:/root/small.bin TCP4:__GW__:10003
+guest	socat -u OPEN:/root/small.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __BASEPATH__/small.bin __TEMP_SMALL__
 
@@ -55,9 +54,8 @@ guest	cmp /root/big.bin test_big.bin
 
 test	TCP/IPv6: guest to host: big transfer
 hostb	socat -u TCP6-LISTEN:10003,bind=[::1],reuseaddr OPEN:__TEMP_BIG__,create,trunc
-gout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
-guest	socat -u OPEN:/root/big.bin TCP6:[__GW6__%__IFNAME__]:10003
+guest	socat -u OPEN:/root/big.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __BASEPATH__/big.bin __TEMP_BIG__
 
@@ -71,6 +69,6 @@ guest	cmp /root/small.bin test_small.bin
 test	TCP/IPv6: guest to host: small transfer
 hostb	socat -u TCP6-LISTEN:10003,bind=[::1],reuseaddr OPEN:__TEMP_SMALL__,create,trunc
 sleep	1
-guest	socat -u OPEN:/root/small.bin TCP6:[__GW6__%__IFNAME__]:10003
+guest	socat -u OPEN:/root/small.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __BASEPATH__/small.bin __TEMP_SMALL__
diff --git a/test/passt/udp b/test/passt/udp
index 80d0fa3..d358b29 100644
--- a/test/passt/udp
+++ b/test/passt/udp
@@ -25,8 +25,7 @@ guest	cmp /root/medium.bin test.bin
 
 test	UDP/IPv4: guest to host
 hostb	socat -u UDP4-LISTEN:10003,bind=127.0.0.1,null-eof OPEN:__TEMP__,create,trunc
-gout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-guest	socat -u OPEN:/root/medium.bin UDP4:__GW__:10003,shut-null
+guest	socat -u OPEN:/root/medium.bin UDP4:__NAT_TO_HOST4__:10003,shut-null
 hostw
 check	cmp __BASEPATH__/medium.bin __TEMP__
 
@@ -41,6 +40,6 @@ test	UDP/IPv6: guest to host
 hostb	socat -u UDP6-LISTEN:10003,bind=[::1],null-eof OPEN:__TEMP__,create,trunc
 gout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
-guest	socat -u OPEN:/root/medium.bin UDP6:[__GW6__%__IFNAME__]:10003,shut-null
+guest	socat -u OPEN:/root/medium.bin UDP6:[__NAT_TO_HOST6__%__IFNAME__]:10003,shut-null
 hostw
 check	cmp __BASEPATH__/medium.bin __TEMP__
diff --git a/test/passt_in_ns/tcp b/test/passt_in_ns/tcp
index cdb7060..51d0379 100644
--- a/test/passt_in_ns/tcp
+++ b/test/passt_in_ns/tcp
@@ -36,16 +36,15 @@ check	cmp __TEMP_NS_BIG__ __BASEPATH__/big.bin
 
 test	TCP/IPv4: guest to host: big transfer
 hostb	socat -u TCP4-LISTEN:10003 OPEN:__TEMP_BIG__,create,trunc
-gout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
 sleep	1
-guest	socat -u OPEN:/root/big.bin TCP4:__GW__:10003
+guest	socat -u OPEN:/root/big.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __TEMP_BIG__ __BASEPATH__/big.bin
 
 test	TCP/IPv4: guest to ns: big transfer
 nsb	socat -u TCP4-LISTEN:10002 OPEN:__TEMP_NS_BIG__,create,trunc
 sleep	1
-guest	socat -u OPEN:/root/big.bin TCP4:__GW__:10002
+guest	socat -u OPEN:/root/big.bin TCP4:__NAT_TO_NS4__:10002
 nsw
 check	cmp __TEMP_NS_BIG__ __BASEPATH__/big.bin
 
@@ -59,7 +58,7 @@ check	cmp __TEMP_BIG__ __BASEPATH__/big.bin
 test	TCP/IPv4: ns to host (via tap): big transfer
 hostb	socat -u TCP4-LISTEN:10003 OPEN:__TEMP_BIG__,create,trunc
 sleep	1
-ns	socat -u OPEN:__BASEPATH__/big.bin TCP4:__GW__:10003
+ns	socat -u OPEN:__BASEPATH__/big.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __TEMP_BIG__ __BASEPATH__/big.bin
 
@@ -95,16 +94,15 @@ check	cmp __TEMP_NS_SMALL__ __BASEPATH__/small.bin
 
 test	TCP/IPv4: guest to host: small transfer
 hostb	socat -u TCP4-LISTEN:10003 OPEN:__TEMP_SMALL__,create,trunc
-gout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
 sleep	1
-guest	socat -u OPEN:/root/small.bin TCP4:__GW__:10003
+guest	socat -u OPEN:/root/small.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __TEMP_SMALL__ __BASEPATH__/small.bin
 
 test	TCP/IPv4: guest to ns: small transfer
 nsb	socat -u TCP4-LISTEN:10002 OPEN:__TEMP_NS_SMALL__,create,trunc
 sleep	1
-guest	socat -u OPEN:/root/small.bin TCP4:__GW__:10002
+guest	socat -u OPEN:/root/small.bin TCP4:__NAT_TO_NS4__:10002
 nsw
 check	cmp __TEMP_NS_SMALL__ __BASEPATH__/small.bin
 
@@ -118,7 +116,7 @@ check	cmp __TEMP_SMALL__ __BASEPATH__/small.bin
 test	TCP/IPv4: ns to host (via tap): small transfer
 hostb	socat -u TCP4-LISTEN:10003 OPEN:__TEMP_SMALL__,create,trunc
 sleep	1
-ns	socat -u OPEN:__BASEPATH__/small.bin TCP4:__GW__:10003
+ns	socat -u OPEN:__BASEPATH__/small.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __TEMP_SMALL__ __BASEPATH__/small.bin
 
@@ -152,17 +150,16 @@ check	cmp __TEMP_NS_BIG__ __BASEPATH__/big.bin
 
 test	TCP/IPv6: guest to host: big transfer
 hostb	socat -u TCP6-LISTEN:10003 OPEN:__TEMP_BIG__,create,trunc
-gout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 sleep	1
-guest	socat -u OPEN:/root/big.bin TCP6:[__GW6__%__IFNAME__]:10003
+guest	socat -u OPEN:/root/big.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __TEMP_BIG__ __BASEPATH__/big.bin
 
 test	TCP/IPv6: guest to ns: big transfer
 nsb	socat -u TCP6-LISTEN:10002 OPEN:__TEMP_NS_BIG__,create,trunc
 sleep	1
-guest	socat -u OPEN:/root/big.bin TCP6:[__GW6__%__IFNAME__]:10002
+guest	socat -u OPEN:/root/big.bin TCP6:[__NAT_TO_NS6__%__IFNAME__]:10002
 nsw
 check	cmp __TEMP_NS_BIG__ __BASEPATH__/big.bin
 
@@ -177,7 +174,7 @@ test	TCP/IPv6: ns to host (via tap): big transfer
 hostb	socat -u TCP6-LISTEN:10003 OPEN:__TEMP_BIG__,create,trunc
 nsout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 sleep	1
-ns	socat -u OPEN:__BASEPATH__/big.bin TCP6:[__GW6__%__IFNAME__]:10003
+ns	socat -u OPEN:__BASEPATH__/big.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __TEMP_BIG__ __BASEPATH__/big.bin
 
@@ -212,17 +209,16 @@ check	cmp __TEMP_NS_SMALL__ __BASEPATH__/small.bin
 
 test	TCP/IPv6: guest to host: small transfer
 hostb	socat -u TCP6-LISTEN:10003 OPEN:__TEMP_SMALL__,create,trunc
-gout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 sleep	1
-guest	socat -u OPEN:/root/small.bin TCP6:[__GW6__%__IFNAME__]:10003
+guest	socat -u OPEN:/root/small.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __TEMP_SMALL__ __BASEPATH__/small.bin
 
 test	TCP/IPv6: guest to ns: small transfer
 nsb	socat -u TCP6-LISTEN:10002 OPEN:__TEMP_NS_SMALL__
 sleep	1
-guest	socat -u OPEN:/root/small.bin TCP6:[__GW6__%__IFNAME__]:10002
+guest	socat -u OPEN:/root/small.bin TCP6:[__NAT_TO_NS6__%__IFNAME__]:10002
 nsw
 check	cmp __TEMP_NS_SMALL__ __BASEPATH__/small.bin
 
@@ -237,7 +233,7 @@ test	TCP/IPv6: ns to host (via tap): small transfer
 hostb	socat -u TCP6-LISTEN:10003 OPEN:__TEMP_SMALL__,create,trunc
 nsout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 sleep	1
-ns	socat -u OPEN:__BASEPATH__/small.bin TCP6:[__GW6__%__IFNAME__]:10003
+ns	socat -u OPEN:__BASEPATH__/small.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __TEMP_SMALL__ __BASEPATH__/small.bin
 
diff --git a/test/passt_in_ns/udp b/test/passt_in_ns/udp
index 8a02513..40e687f 100644
--- a/test/passt_in_ns/udp
+++ b/test/passt_in_ns/udp
@@ -34,16 +34,15 @@ check	cmp __TEMP_NS__ __BASEPATH__/medium.bin
 
 test	UDP/IPv4: guest to host
 hostb	socat -u UDP4-LISTEN:10003,null-eof OPEN:__TEMP__,create,trunc
-gout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
 sleep	1
-guest	socat -u OPEN:/root/medium.bin UDP4:__GW__:10003,shut-null
+guest	socat -u OPEN:/root/medium.bin UDP4:__NAT_TO_HOST4__:10003,shut-null
 hostw
 check	cmp __TEMP__ __BASEPATH__/medium.bin
 
 test	UDP/IPv4: guest to ns
 nsb	socat -u UDP4-LISTEN:10002,null-eof OPEN:__TEMP_NS__,create,trunc
 sleep	1
-guest	socat -u OPEN:/root/medium.bin UDP4:__GW__:10002,shut-null
+guest	socat -u OPEN:/root/medium.bin UDP4:__NAT_TO_NS4__:10002,shut-null
 nsw
 check	cmp __TEMP_NS__ __BASEPATH__/medium.bin
 
@@ -57,7 +56,7 @@ check	cmp __TEMP__ __BASEPATH__/medium.bin
 test	UDP/IPv4: ns to host (via tap)
 hostb	socat -u UDP4-LISTEN:10003,null-eof OPEN:__TEMP__,create,trunc
 sleep	1
-ns	socat -u OPEN:__BASEPATH__/medium.bin UDP4:__GW__:10003,shut-null
+ns	socat -u OPEN:__BASEPATH__/medium.bin UDP4:__NAT_TO_HOST4__:10003,shut-null
 hostw
 check	cmp __TEMP__ __BASEPATH__/medium.bin
 
@@ -93,17 +92,16 @@ check	cmp __TEMP_NS__ __BASEPATH__/medium.bin
 
 test	UDP/IPv6: guest to host
 hostb	socat -u UDP6-LISTEN:10003,null-eof OPEN:__TEMP__,create,trunc
-gout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 sleep	1
-guest	socat -u OPEN:/root/medium.bin UDP6:[__GW6__%__IFNAME__]:10003,shut-null
+guest	socat -u OPEN:/root/medium.bin UDP6:[__NAT_TO_HOST6__%__IFNAME__]:10003,shut-null
 hostw
 check	cmp __TEMP__ __BASEPATH__/medium.bin
 
 test	UDP/IPv6: guest to ns
 nsb	socat -u UDP6-LISTEN:10002,null-eof OPEN:__TEMP_NS__,create,trunc
 sleep	1
-guest	socat -u OPEN:/root/medium.bin UDP6:[__GW6__%__IFNAME__]:10002,shut-null
+guest	socat -u OPEN:/root/medium.bin UDP6:[__NAT_TO_NS6__%__IFNAME__]:10002,shut-null
 nsw
 check	cmp __TEMP_NS__ __BASEPATH__/medium.bin
 
@@ -118,7 +116,7 @@ test	UDP/IPv6: ns to host (via tap)
 hostb	socat -u UDP6-LISTEN:10003,null-eof OPEN:__TEMP__,create,trunc
 nsout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 sleep	1
-ns	socat -u OPEN:__BASEPATH__/medium.bin UDP6:[__GW6__%__IFNAME__]:10003,shut-null
+ns	socat -u OPEN:__BASEPATH__/medium.bin UDP6:[__NAT_TO_HOST6__%__IFNAME__]:10003,shut-null
 hostw
 check	cmp __TEMP__ __BASEPATH__/medium.bin
 
diff --git a/test/pasta/tcp b/test/pasta/tcp
index 6ab18c5..4f6684f 100644
--- a/test/pasta/tcp
+++ b/test/pasta/tcp
@@ -33,8 +33,7 @@ check	cmp __BASEPATH__/big.bin __TEMP_BIG__
 
 test	TCP/IPv4: ns to host (via tap): big transfer
 hostb	socat -u TCP4-LISTEN:10003 OPEN:__TEMP_BIG__,create,trunc
-nsout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-ns	socat -u OPEN:__BASEPATH__/big.bin TCP4:__GW__:10003
+ns	socat -u OPEN:__BASEPATH__/big.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __BASEPATH__/big.bin __TEMP_BIG__
 
@@ -52,8 +51,7 @@ check	cmp __BASEPATH__/small.bin __TEMP_SMALL__
 
 test	TCP/IPv4: ns to host (via tap): small transfer
 hostb	socat -u TCP4-LISTEN:10003 OPEN:__TEMP_SMALL__,create,trunc
-nsout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-ns	socat -u OPEN:__BASEPATH__/small.bin TCP4:__GW__:10003
+ns	socat -u OPEN:__BASEPATH__/small.bin TCP4:__NAT_TO_HOST4__:10003
 hostw
 check	cmp __BASEPATH__/small.bin __TEMP_SMALL__
 
@@ -71,9 +69,8 @@ check	cmp __BASEPATH__/big.bin __TEMP_BIG__
 
 test	TCP/IPv6: ns to host (via tap): big transfer
 hostb	socat -u TCP6-LISTEN:10003 OPEN:__TEMP_BIG__,create,trunc
-nsout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 nsout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
-ns	socat -u OPEN:__BASEPATH__/big.bin TCP6:[__GW6__%__IFNAME__]:10003
+ns	socat -u OPEN:__BASEPATH__/big.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __BASEPATH__/big.bin __TEMP_BIG__
 
@@ -91,6 +88,6 @@ check	cmp __BASEPATH__/small.bin __TEMP_SMALL__
 
 test	TCP/IPv6: ns to host (via tap): small transfer
 hostb	socat -u TCP6-LISTEN:10003 OPEN:__TEMP_SMALL__,create,trunc
-ns	socat -u OPEN:__BASEPATH__/small.bin TCP6:[__GW6__%__IFNAME__]:10003
+ns	socat -u OPEN:__BASEPATH__/small.bin TCP6:[__NAT_TO_HOST6__%__IFNAME__]:10003
 hostw
 check	cmp __BASEPATH__/small.bin __TEMP_SMALL__
diff --git a/test/pasta/udp b/test/pasta/udp
index 30e3a85..bd87948 100644
--- a/test/pasta/udp
+++ b/test/pasta/udp
@@ -32,8 +32,7 @@ check	cmp __BASEPATH__/medium.bin __TEMP__
 
 test	UDP/IPv4: ns to host (via tap)
 hostb	socat -u UDP4-LISTEN:10003,null-eof OPEN:__TEMP__,create,trunc
-nsout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-ns	socat -u OPEN:__BASEPATH__/medium.bin UDP4:__GW__:10003,shut-null
+ns	socat -u OPEN:__BASEPATH__/medium.bin UDP4:__NAT_TO_HOST4__:10003,shut-null
 hostw
 check	cmp __BASEPATH__/medium.bin __TEMP__
 
@@ -52,8 +51,7 @@ check	cmp __BASEPATH__/medium.bin __TEMP__
 
 test	UDP/IPv6: ns to host (via tap)
 hostb	socat -u UDP6-LISTEN:10003,null-eof OPEN:__TEMP__,create,trunc
-nsout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 nsout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
-ns	socat -u OPEN:__BASEPATH__/medium.bin UDP6:[__GW6__%__IFNAME__]:10003,shut-null
+ns	socat -u OPEN:__BASEPATH__/medium.bin UDP6:[__NAT_TO_HOST6__%__IFNAME__]:10003,shut-null
 hostw
 check	cmp __BASEPATH__/medium.bin __TEMP__
diff --git a/test/perf/passt_tcp b/test/perf/passt_tcp
index 7046f3c..7852a7e 100644
--- a/test/perf/passt_tcp
+++ b/test/perf/passt_tcp
@@ -29,8 +29,6 @@ ns	/sbin/sysctl -w net.ipv4.tcp_rmem="4096 524288 134217728"
 ns	/sbin/sysctl -w net.ipv4.tcp_wmem="4096 524288 134217728"
 ns	/sbin/sysctl -w net.ipv4.tcp_timestamps=0
 
-gout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-gout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 
 hout	FREQ_PROCFS (echo "scale=1"; sed -n 's/cpu MHz.*: \([0-9]*\)\..*$/(\1+10^2\/2)\/10^3/p' /proc/cpuinfo) | bc -l | head -n1
@@ -54,16 +52,16 @@ bw	-
 bw	-
 
 guest	ip link set dev __IFNAME__ mtu 1280
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
 bw	__BW__ 1.2 1.5
 guest	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
 bw	__BW__ 1.6 1.8
 guest	ip link set dev __IFNAME__ mtu 9000
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 8M
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 8M
 bw	__BW__ 4.0 5.0
 guest	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 16M
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 16M
 bw	__BW__ 7.0 8.0
 
 tl	TCP RR latency over IPv6: guest to host
@@ -73,7 +71,7 @@ lat	-
 lat	-
 lat	-
 nsb	tcp_rr --nolog -6
-gout	LAT tcp_rr --nolog -6 -c -H __GW6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
+gout	LAT tcp_rr --nolog -6 -c -H __NAT_TO_NS6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
 lat	__LAT__ 200 150
 
 tl	TCP CRR latency over IPv6: guest to host
@@ -83,28 +81,28 @@ lat	-
 lat	-
 lat	-
 nsb	tcp_crr --nolog -6
-gout	LAT tcp_crr --nolog -6 -c -H __GW6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
+gout	LAT tcp_crr --nolog -6 -c -H __NAT_TO_NS6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
 lat	__LAT__ 500 400
 
 
 tr	TCP throughput over IPv4: guest to host
 guest	ip link set dev __IFNAME__ mtu 256
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 1M
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 1M
 bw	__BW__ 0.2 0.3
 guest	ip link set dev __IFNAME__ mtu 576
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 1M
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 1M
 bw	__BW__ 0.5 0.8
 guest	ip link set dev __IFNAME__ mtu 1280
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
 bw	__BW__ 1.2 1.5
 guest	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 4M
 bw	__BW__ 1.6 1.8
 guest	ip link set dev __IFNAME__ mtu 9000
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 8M
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 8M
 bw	__BW__ 4.0 5.0
 guest	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 16M
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -w 16M
 bw	__BW__ 7.0 8.0
 
 tl	TCP RR latency over IPv4: guest to host
@@ -114,7 +112,7 @@ lat	-
 lat	-
 lat	-
 nsb	tcp_rr --nolog -4
-gout	LAT tcp_rr --nolog -4 -c -H __GW__ | sed -n 's/^throughput=\(.*\)/\1/p'
+gout	LAT tcp_rr --nolog -4 -c -H __NAT_TO_NS4__ | sed -n 's/^throughput=\(.*\)/\1/p'
 lat	__LAT__ 200 150
 
 tl	TCP CRR latency over IPv4: guest to host
@@ -124,7 +122,7 @@ lat	-
 lat	-
 lat	-
 nsb	tcp_crr --nolog -4
-gout	LAT tcp_crr --nolog -4 -c -H __GW__ | sed -n 's/^throughput=\(.*\)/\1/p'
+gout	LAT tcp_crr --nolog -4 -c -H __NAT_TO_NS4__ | sed -n 's/^throughput=\(.*\)/\1/p'
 lat	__LAT__ 500 400
 
 
diff --git a/test/perf/passt_udp b/test/perf/passt_udp
index a117b6a..e19dd8c 100644
--- a/test/perf/passt_udp
+++ b/test/perf/passt_udp
@@ -22,8 +22,6 @@ guest	/sbin/sysctl -w net.core.wmem_max=16777216
 guest	/sbin/sysctl -w net.core.rmem_default=16777216
 guest	/sbin/sysctl -w net.core.wmem_default=16777216
 
-gout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-gout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 
 hout	FREQ_PROCFS (echo "scale=1"; sed -n 's/cpu MHz.*: \([0-9]*\)\..*$/(\1+10^2\/2)\/10^3/p' /proc/cpuinfo) | bc -l | head -n1
@@ -46,16 +44,16 @@ tr	UDP throughput over IPv6: guest to host
 bw	-
 bw	-
 guest	ip link set dev __IFNAME__ mtu 1280
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 2G
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 2G
 bw	__BW__ 0.8 1.2
 guest	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 3G
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 3G
 bw	__BW__ 1.0 1.5
 guest	ip link set dev __IFNAME__ mtu 9000
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 5G
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 5G
 bw	__BW__ 4.0 5.0
 guest	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW guest ns __GW6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 7G
+iperf3	BW guest ns __NAT_TO_NS6__%__IFNAME__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 7G
 bw	__BW__ 4.0 5.0
 
 tl	UDP RR latency over IPv6: guest to host
@@ -65,28 +63,28 @@ lat	-
 lat	-
 lat	-
 nsb	udp_rr --nolog -6
-gout	LAT udp_rr --nolog -6 -c -H __GW6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
+gout	LAT udp_rr --nolog -6 -c -H __NAT_TO_NS6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
 lat	__LAT__ 200 150
 
 
 tr	UDP throughput over IPv4: guest to host
 guest	ip link set dev __IFNAME__ mtu 256
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 500M
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 500M
 bw	__BW__ 0.0 0.0
 guest	ip link set dev __IFNAME__ mtu 576
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 1G
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 1G
 bw	__BW__ 0.4 0.6
 guest	ip link set dev __IFNAME__ mtu 1280
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 2G
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 2G
 bw	__BW__ 0.8 1.2
 guest	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 3G
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 3G
 bw	__BW__ 1.0 1.5
 guest	ip link set dev __IFNAME__ mtu 9000
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 6G
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 6G
 bw	__BW__ 4.0 5.0
 guest	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW guest ns __GW__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 7G
+iperf3	BW guest ns __NAT_TO_NS4__ 100${i}2 __THREADS__ __TIME__ __OPTS__ -b 7G
 bw	__BW__ 4.0 5.0
 
 tl	UDP RR latency over IPv4: guest to host
@@ -96,7 +94,7 @@ lat	-
 lat	-
 lat	-
 nsb	udp_rr --nolog -4
-gout	LAT udp_rr --nolog -4 -c -H __GW__ | sed -n 's/^throughput=\(.*\)/\1/p'
+gout	LAT udp_rr --nolog -4 -c -H __NAT_TO_NS4__ | sed -n 's/^throughput=\(.*\)/\1/p'
 lat	__LAT__ 200 150
 
 
diff --git a/test/perf/pasta_tcp b/test/perf/pasta_tcp
index 4b13384..8053800 100644
--- a/test/perf/pasta_tcp
+++ b/test/perf/pasta_tcp
@@ -162,8 +162,6 @@ te
 
 test	pasta: throughput and latency (connections via tap)
 
-nsout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-nsout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 nsout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 set	THREADS 1
 set	STREAMS 2
@@ -177,16 +175,16 @@ th	MTU 1500B 4000B 16384B 65520B
 
 tr	TCP throughput over IPv6: ns to host
 ns	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 512k
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 512k
 bw	__BW__ 0.2 0.4
 ns	ip link set dev __IFNAME__ mtu 4000
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 1M
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 1M
 bw	__BW__ 0.3 0.5
 ns	ip link set dev __IFNAME__ mtu 16384
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
 bw	__BW__ 1.5 2.0
 ns	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
 bw	__BW__ 2.0 2.5
 
 tl	TCP RR latency over IPv6: ns to host
@@ -194,7 +192,7 @@ lat	-
 lat	-
 lat	-
 hostb	tcp_rr --nolog -P 10003 -C 10013 -6
-nsout	LAT tcp_rr --nolog -P 10003 -C 10013 -6 -c -H __GW6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
+nsout	LAT tcp_rr --nolog -P 10003 -C 10013 -6 -c -H __NAT_TO_HOST6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
 hostw
 lat	__LAT__ 150 100
 
@@ -203,23 +201,23 @@ lat	-
 lat	-
 lat	-
 hostb	tcp_crr --nolog -P 10003 -C 10013 -6
-nsout	LAT tcp_crr --nolog -P 10003 -C 10013 -6 -c -H __GW6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
+nsout	LAT tcp_crr --nolog -P 10003 -C 10013 -6 -c -H __NAT_TO_HOST6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
 hostw
 lat	__LAT__ 1500 500
 
 
 tr	TCP throughput over IPv4: ns to host
 ns	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 512k
+iperf3	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 512k
 bw	__BW__ 0.2 0.4
 ns	ip link set dev __IFNAME__ mtu 4000
-iperf3s	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 1M
+iperf3s	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 1M
 bw	__BW__ 0.3 0.5
 ns	ip link set dev __IFNAME__ mtu 16384
-iperf3	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
+iperf3	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
 bw	__BW__ 1.5 2.0
 ns	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
+iperf3	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -w 8M
 bw	__BW__ 2.0 2.5
 
 tl	TCP RR latency over IPv4: ns to host
@@ -227,7 +225,7 @@ lat	-
 lat	-
 lat	-
 hostb	tcp_rr --nolog -P 10003 -C 10013 -4
-nsout	LAT tcp_rr --nolog -P 10003 -C 10013 -4 -c -H __GW__ | sed -n 's/^throughput=\(.*\)/\1/p'
+nsout	LAT tcp_rr --nolog -P 10003 -C 10013 -4 -c -H __NAT_TO_HOST4__ | sed -n 's/^throughput=\(.*\)/\1/p'
 hostw
 lat	__LAT__ 150 100
 
@@ -236,7 +234,7 @@ lat	-
 lat	-
 lat	-
 hostb	tcp_crr --nolog -P 10003 -C 10013 -4
-nsout	LAT tcp_crr --nolog -P 10003 -C 10013 -4 -c -H __GW__ | sed -n 's/^throughput=\(.*\)/\1/p'
+nsout	LAT tcp_crr --nolog -P 10003 -C 10013 -4 -c -H __NAT_TO_HOST4__ | sed -n 's/^throughput=\(.*\)/\1/p'
 hostw
 lat	__LAT__ 1500 500
 
diff --git a/test/perf/pasta_udp b/test/perf/pasta_udp
index 7007b6f..1d3d5d4 100644
--- a/test/perf/pasta_udp
+++ b/test/perf/pasta_udp
@@ -123,8 +123,6 @@ te
 
 test	pasta: throughput and latency (traffic via tap)
 
-nsout	GW ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
-nsout	GW6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 nsout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
 
 info	Throughput in Gbps, latency in ��s, one thread at __FREQ__ GHz, __STREAMS__ streams
@@ -134,16 +132,16 @@ th	MTU 1500B 4000B 16384B 65520B
 
 tr	UDP throughput over IPv6: ns to host
 ns	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 2G
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 2G
 bw	__BW__ 0.3 0.5
 ns	ip link set dev __IFNAME__ mtu 4000
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 3G
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 3G
 bw	__BW__ 0.5 0.8
 ns	ip link set dev __IFNAME__ mtu 16384
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 4G
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 4G
 bw	__BW__ 3.0 4.0
 ns	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW ns host __GW6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 6G
+iperf3	BW ns host __NAT_TO_HOST6__%__IFNAME__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 6G
 bw	__BW__ 6.0 7.0
 
 tl	UDP RR latency over IPv6: ns to host
@@ -151,23 +149,23 @@ lat	-
 lat	-
 lat	-
 hostb	udp_rr --nolog -P 10003 -C 10013 -6
-nsout	LAT udp_rr --nolog -P 10003 -C 10013 -6 -c -H __GW6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
+nsout	LAT udp_rr --nolog -P 10003 -C 10013 -6 -c -H __NAT_TO_HOST6__%__IFNAME__ | sed -n 's/^throughput=\(.*\)/\1/p'
 hostw
 lat	__LAT__ 200 150
 
 
 tr	UDP throughput over IPv4: ns to host
 ns	ip link set dev __IFNAME__ mtu 1500
-iperf3	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 2G
+iperf3	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 2G
 bw	__BW__ 0.3 0.5
 ns	ip link set dev __IFNAME__ mtu 4000
-iperf3	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 3G
+iperf3	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 3G
 bw	__BW__ 0.5 0.8
 ns	ip link set dev __IFNAME__ mtu 16384
-iperf3	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 4G
+iperf3	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 4G
 bw	__BW__ 3.0 4.0
 ns	ip link set dev __IFNAME__ mtu 65520
-iperf3	BW ns host __GW__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 6G
+iperf3	BW ns host __NAT_TO_HOST4__ 100${i}3 __THREADS__ __TIME__ __OPTS__ -b 6G
 bw	__BW__ 6.0 7.0
 
 tl	UDP RR latency over IPv4: ns to host
@@ -175,7 +173,7 @@ lat	-
 lat	-
 lat	-
 hostb	udp_rr --nolog -P 10003 -C 10013 -4
-nsout	LAT udp_rr --nolog -P 10003 -C 10013 -4 -c -H __GW__ | sed -n 's/^throughput=\(.*\)/\1/p'
+nsout	LAT udp_rr --nolog -P 10003 -C 10013 -4 -c -H __NAT_TO_HOST4__ | sed -n 's/^throughput=\(.*\)/\1/p'
 hostw
 lat	__LAT__ 200 150
 
diff --git a/test/two_guests/basic b/test/two_guests/basic
index 09fbd3e..b948757 100644
--- a/test/two_guests/basic
+++ b/test/two_guests/basic
@@ -46,18 +46,16 @@ check	[ "__ADDR1_6__" = "__HOST_ADDR6__" ]
 check	[ "__ADDR2_6__" = "__HOST_ADDR6__" ]
 
 test	TCP/IPv4: guest 1 > guest 2
-g1out	GW1 ip -j -4 route show|jq -rM '.[] | select(.dst == "default").gateway'
 guest2b	socat -u TCP4-LISTEN:10004 OPEN:msg,create,trunc
-guest1	echo "Hello_from_guest_1" | socat -u STDIN TCP4:__GW1__:10004
+guest1	echo "Hello_from_guest_1" | socat -u STDIN TCP4:__NAT_TO_HOST4__:10004
 guest2w
 sleep	1
 g2out	MSG2 cat msg
 check	[ "__MSG2__" = "Hello_from_guest_1" ]
 
 test	TCP/IPv6: guest 2 > guest 1
-g2out	GW2_6 ip -j -6 route show|jq -rM '.[] | select(.dst == "default").gateway'
 guest1b	socat -u TCP6-LISTEN:10001 OPEN:msg,create,trunc
-guest2	echo "Hello_from_guest_2" | socat -u STDIN TCP6:[__GW2_6__%__IFNAME2__]:10001
+guest2	echo "Hello_from_guest_2" | socat -u STDIN TCP6:[__NAT_TO_HOST6__%__IFNAME2__]:10001
 guest1w
 sleep	1
 g1out	MSG1 cat msg
@@ -65,7 +63,7 @@ check	[ "__MSG1__" = "Hello_from_guest_2" ]
 
 test	UDP/IPv4: guest 1 > guest 2
 guest2b	socat -u TCP4-LISTEN:10004 OPEN:msg,create,trunc
-guest1	echo "Hello_from_guest_1" | socat -u STDIN TCP4:__GW1__:10004
+guest1	echo "Hello_from_guest_1" | socat -u STDIN TCP4:__NAT_TO_HOST4__:10004
 guest2w
 sleep	1
 g2out	MSG2 cat msg
@@ -73,7 +71,7 @@ check	[ "__MSG2__" = "Hello_from_guest_1" ]
 
 test	UDP/IPv6: guest 2 > guest 1
 guest1b	socat -u TCP6-LISTEN:10001 OPEN:msg,create,trunc
-guest2	echo "Hello_from_guest_2" | socat -u STDIN TCP6:[__GW2_6__%__IFNAME2__]:10001
+guest2	echo "Hello_from_guest_2" | socat -u STDIN TCP6:[__NAT_TO_HOST6__%__IFNAME2__]:10001
 guest1w
 sleep	1
 g1out	MSG1 cat msg
diff --git a/udp.c b/udp.c
index 9c96c0f..1533cee 100644
--- a/udp.c
+++ b/udp.c
@@ -597,7 +597,7 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 	} else if (IN4_IS_ADDR_LOOPBACK(&b->s_in.sin_addr) ||
 		   IN4_IS_ADDR_UNSPECIFIED(&b->s_in.sin_addr)||
 		   IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.addr_seen)) {
-		b->iph.saddr = c->ip4.gw.s_addr;
+		b->iph.saddr = c->ip4.nattohost.s_addr;
 		udp_tap_map[V4][src_port].ts = now->tv_sec;
 		udp_tap_map[V4][src_port].flags |= PORT_LOCAL;
 
@@ -662,8 +662,8 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
 
 		bitmap_set(udp_act[V6][UDP_ACT_TAP], src_port);
 
-		if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
-			src = &c->ip6.gw;
+		if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.nattohost))
+			src = &c->ip6.nattohost;
 		else
 			src = &c->ip6.addr_ll;
 	}
@@ -841,7 +841,7 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 		if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.dns_match) &&
 		    ntohs(s_in.sin_port) == 53) {
 			s_in.sin_addr = c->ip4.dns_host;
-		} else if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.gw) &&
+		} else if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.nattohost) &&
 			   !c->no_map_gw) {
 			if (!(udp_tap_map[V4][dst].flags & PORT_LOCAL) ||
 			    (udp_tap_map[V4][dst].flags & PORT_LOOPBACK))
@@ -887,7 +887,7 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 		if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.dns_match) &&
 		    ntohs(s_in6.sin6_port) == 53) {
 			s_in6.sin6_addr = c->ip6.dns_host;
-		} else if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.gw) &&
+		} else if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.nattohost) &&
 			   !c->no_map_gw) {
 			if (!(udp_tap_map[V6][dst].flags & PORT_LOCAL) ||
 			    (udp_tap_map[V6][dst].flags & PORT_LOOPBACK))
-- 
@@ -597,7 +597,7 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 	} else if (IN4_IS_ADDR_LOOPBACK(&b->s_in.sin_addr) ||
 		   IN4_IS_ADDR_UNSPECIFIED(&b->s_in.sin_addr)||
 		   IN4_ARE_ADDR_EQUAL(&b->s_in.sin_addr, &c->ip4.addr_seen)) {
-		b->iph.saddr = c->ip4.gw.s_addr;
+		b->iph.saddr = c->ip4.nattohost.s_addr;
 		udp_tap_map[V4][src_port].ts = now->tv_sec;
 		udp_tap_map[V4][src_port].flags |= PORT_LOCAL;
 
@@ -662,8 +662,8 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
 
 		bitmap_set(udp_act[V6][UDP_ACT_TAP], src_port);
 
-		if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.gw))
-			src = &c->ip6.gw;
+		if (IN6_IS_ADDR_LINKLOCAL(&c->ip6.nattohost))
+			src = &c->ip6.nattohost;
 		else
 			src = &c->ip6.addr_ll;
 	}
@@ -841,7 +841,7 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 		if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.dns_match) &&
 		    ntohs(s_in.sin_port) == 53) {
 			s_in.sin_addr = c->ip4.dns_host;
-		} else if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.gw) &&
+		} else if (IN4_ARE_ADDR_EQUAL(&s_in.sin_addr, &c->ip4.nattohost) &&
 			   !c->no_map_gw) {
 			if (!(udp_tap_map[V4][dst].flags & PORT_LOCAL) ||
 			    (udp_tap_map[V4][dst].flags & PORT_LOOPBACK))
@@ -887,7 +887,7 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
 		if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.dns_match) &&
 		    ntohs(s_in6.sin6_port) == 53) {
 			s_in6.sin6_addr = c->ip6.dns_host;
-		} else if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.gw) &&
+		} else if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.nattohost) &&
 			   !c->no_map_gw) {
 			if (!(udp_tap_map[V6][dst].flags & PORT_LOCAL) ||
 			    (udp_tap_map[V6][dst].flags & PORT_LOOPBACK))
-- 
2.40.1