simpletun

Simple half duplex tunnel

Host A(172.18.0.2)

./simpletun -s -i tun0 
ip route add a.a.a.a/b dev tun0

Host B(172.18.0.1)

./simpletun -i tun0 -c 172.18.0.2 
ip route add c.c.c.c/d dev tun0

Host A ------------------------------------ Host B

On host A, the flow to a.a.a.a/b will go through the tunnel. On host B, the flow to c.c.c.c/d will go through the tunnel.

....

Why is it half duplex? Because SimpleTun has only one thread and can only handle one direction at a time.

for tunnat:

Host A -----------------Host M------------------- Host B On host A:

ifconfig enp0s9 172.16.0.1/24
route add -host 172.18.0.1 gw 172.16.0.2

On host M:

ifconfig enp0s9 172.16.0.2/24
ifconfig enp0s10 172.18.0.2/24
./tunnat -i tun1 -o 172.16.0.1 -m 123.110.0.1
ip rule add from 172.16.0.1 tab tunnat
ip route add default dev tun1
ip route add 123.110.0.1/32 dev tun1

On host B:

ifconfig enp0s10 172.18.0.1/24
route add default gw 172.18.0.2

Host A ping Host B ping 172.18.0.1

07:48:02.584525 IP 123.110.0.1 > 172.18.0.1: ICMP echo request, id 5, seq 2167, length 64
07:48:02.584795 IP 172.18.0.1 > 123.110.0.1: ICMP echo reply, id 5, seq 2167, length 64
07:48:03.612804 IP 123.110.0.1 > 172.18.0.1: ICMP echo request, id 5, seq 2168, length 64
07:48:03.613082 IP 172.18.0.1 > 123.110.0.1: ICMP echo reply, id 5, seq 2168, length 64
07:48:04.639537 IP 123.110.0.1 > 172.18.0.1: ICMP echo request, id 5, seq 2169, length 64
07:48:04.639939 IP 172.18.0.1 > 123.110.0.1: ICMP echo reply, id 5, seq 2169, length 64
07:48:05.667918 IP 123.110.0.1 > 172.18.0.1: ICMP echo request, id 5, seq 2170, length 64
07:48:05.668204 IP 172.18.0.1 > 123.110.0.1: ICMP echo reply, id 5, seq 2170, length 64

for tunnat64:

Host A -----------------Host M------------------- Host B

On host A(IPv6 only):

ip -6 addr add dev enp0s8 fdbd:dc03:ff:1:1:227:88:205/64
ip -6 route add default via fe80::dd7:1398:196d:66bf dev enp0s8 # Link-local address fe80::dd7:1398:196d:66bf is at Host M

On host M(NAT6/4):

ifconfig enp0s10 172.18.0.2/24
./tunnat -i tun1 -m 123.110.0.1
ip -6 route add default dev tun1
ip route add 123.110.0.1/32 dev tun1

On host B(IPv4 only):

ifconfig enp0s10 172.18.0.1/24
route add default gw 172.18.0.2

Host A ping Host B ping 64:ff9b::172.18.0.1 Host A:

## ping result
PING 64:ff9b::172.18.0.1(64:ff9b::ac12:1) 56 data bytes
64 bytes from 64:ff9b::ac12:1: icmp_seq=1 ttl=62 time=1.06 ms
64 bytes from 64:ff9b::ac12:1: icmp_seq=2 ttl=62 time=0.983 ms

## tcpdump result
12:06:32.047425 IP6 fdbd:dc03:ff:1:1:227:88:205 > 64:ff9b::ac12:1: ICMP6, echo request, seq 1, length 64
12:06:32.048469 IP6 64:ff9b::ac12:1 > fdbd:dc03:ff:1:1:227:88:205: ICMP6, echo reply, seq 1, length 64
12:06:33.049774 IP6 fdbd:dc03:ff:1:1:227:88:205 > 64:ff9b::ac12:1: ICMP6, echo request, seq 2, length 64
12:06:33.050734 IP6 64:ff9b::ac12:1 > fdbd:dc03:ff:1:1:227:88:205: ICMP6, echo reply, seq 2, length 64

Host B:

## tcpdump result
23:03:52.193734 IP 123.110.0.1 > 172.18.0.1: ICMP echo request, id 13, seq 1, length 64
23:03:52.193765 IP 172.18.0.1 > 123.110.0.1: ICMP echo reply, id 13, seq 1, length 64
23:03:53.196104 IP 123.110.0.1 > 172.18.0.1: ICMP echo request, id 13, seq 2, length 64
23:03:53.196250 IP 172.18.0.1 > 123.110.0.1: ICMP echo reply, id 13, seq 2, length 64

enjoy yourself!