--- /dev/null
+An IPsec <b>transport-mode</b> connection between the natted host <b>alice</b>
+and gateway <b>sun</b> is successfully set up. The client <b>venus</b> behind
+the same NAT as client <b>alice</b> also establishes the same <b>transport-mode</b>
+connection. <b>sun</b> uses the connmark plugin and a <b>%unique</b> mark on
+the CHILD_SAs to select the correct return path SA using connection tracking.
+This allows <b>sun</b> to talk to both nodes for client initiated flows, even
+if the SAs are actually both over <b>moon</b>.<br/>
+To test the connection, both hosts establish an SSH connection to <b>sun</b>.
--- /dev/null
+sun:: ipsec status 2> /dev/null::nat-t.*ESTABLISHED.*sun.strongswan.org.*venus.strongswan.org::YES
+sun:: ipsec status 2> /dev/null::nat-t.*ESTABLISHED.*sun.strongswan.org.*alice@strongswan.org::YES
+alice::ipsec status 2> /dev/null::nat-t.*INSTALLED, TRANSPORT, reqid 1::YES
+venus::ipsec status 2> /dev/null::nat-t.*INSTALLED, TRANSPORT, reqid 1::YES
+alice::ssh 192.168.0.2 'echo alice-echo && exit'::alice-echo::YES
+venus::ssh 192.168.0.2 'echo venus-echo && exit'::venus-echo::YES
+sun::iptables -t mangle -L -n -v
--- /dev/null
+# /etc/ipsec.conf - strongSwan IPsec configuration file
+
+config setup
+
+conn %default
+ ikelifetime=60m
+ keylife=20m
+ rekeymargin=3m
+ keyingtries=1
+
+conn nat-t
+ leftcert=aliceCert.pem
+ leftid=alice@strongswan.org
+ right=192.168.0.2
+ rightid=@sun.strongswan.org
+ type=transport
+ auto=add
--- /dev/null
+# /etc/ipsec.conf - strongSwan IPsec configuration file
+
+config setup
+
+conn %default
+ ikelifetime=60m
+ keylife=20m
+ rekeymargin=3m
+ keyingtries=1
+ left=192.168.0.2
+ leftcert=sunCert.pem
+ leftid=@sun.strongswan.org
+
+conn nat-t
+ right=%any
+ type=transport
+ mark=%unique
+ auto=add
--- /dev/null
+# /etc/strongswan.conf - strongSwan configuration file
+
+charon {
+ load = aes des sha1 sha2 md5 pem pkcs1 gmp random nonce x509 curl revocation hmac xcbc stroke kernel-netlink socket-default connmark
+}
--- /dev/null
+# /etc/ipsec.conf - strongSwan IPsec configuration file
+
+config setup
+
+conn %default
+ ikelifetime=60m
+ keylife=20m
+ rekeymargin=3m
+ keyingtries=1
+
+conn nat-t
+ leftcert=venusCert.pem
+ leftid=venus@strongswan.org
+ right=192.168.0.2
+ rightid=@sun.strongswan.org
+ type=transport
+ auto=add
--- /dev/null
+alice::ipsec stop
+venus::ipsec stop
+sun::ipsec stop
+moon::iptables-restore < /etc/iptables.flush
+sun::iptables-restore < /etc/iptables.flush
--- /dev/null
+moon::iptables-restore < /etc/iptables.rules
+moon::iptables -t nat -A POSTROUTING -o eth0 -s 10.1.0.0/16 -j MASQUERADE
+moon::iptables -A FORWARD -i eth1 -o eth0 -s 10.1.0.0/16 -j ACCEPT
+moon::iptables -A FORWARD -i eth0 -o eth1 -d 10.1.0.0/16 -j ACCEPT
+alice::ipsec start
+venus::ipsec start
+sun::ipsec start
+alice::expect-connection nat-t
+venus::expect-connection nat-t
+alice::ipsec up nat-t
+venus::ipsec up nat-t
--- /dev/null
+#!/bin/bash
+#
+# This configuration file provides information on the
+# guest instances used for this test
+
+# All guest instances that are required for this test
+#
+VIRTHOSTS="alice moon winnetou sun"
+
+# Corresponding block diagram
+#
+DIAGRAM="a-m-w-s-b.png"
+
+# Guest instances on which tcpdump is to be started
+#
+TCPDUMPHOSTS="sun alice venus moon"
+
+# Guest instances on which IPsec is started
+# Used for IPsec logging purposes
+#
+IPSECHOSTS="alice venus sun"