Compile

bash ./script/build.sh

Run

./vpn_linux_amd64 ${PEER_IP} ${PEER_HOST} ${VPN_NETWORK}

Example

Using virtualBox for example(CentOS-7-x86_64-Minimal-1908.iso)

Set NAT network(not NAT)

In this example program, we use TCP tunnel to transmit IP packets, so we must ensure that the two virtual machine networks are connected

virtual machine 1(hostname is vpn1)

ip:10.0.2.6

virtual machine 2(hostname is vpn2)

ip:10.0.2.7

Run the following command in vpn1

create tun device with local ip 192.169.66.1
route packets with destination IP address 192.169.66.0/24 to tun device
create tcp tunnel with peer side(vpn2 10.0.2.7)

[root@vpn-1 /]$ ./vpn_linux_amd64 10.0.2.7 9999 192.169.66.1/24

#-------------------------output-------------------------
2019/12/07 09:03:13 tunIp='192.169.66.1'
2019/12/07 09:03:13 Tun Interface Name: tun0
2019/12/07 09:03:13 exec command 'ip address add 192.169.66.1 dev tun0'
2019/12/07 09:03:13 exec command 'ip link set dev tun0 up'
2019/12/07 09:03:13 exec command 'ip route add table main 192.169.66.0/24 dev tun0'
2019/12/07 09:03:13 non ipv4
2019/12/07 09:03:13 listener on '0.0.0.0:9999'
2019/12/07 09:03:13 try to connect peer
2019/12/07 09:03:13 try to reconnect 1s later, addr=10.0.2.7:9999, err=dial tcp 10.0.2.7:9999: connect: connection refused
2019/12/07 09:03:14 try to reconnect 1s later, addr=10.0.2.7:9999, err=dial tcp 10.0.2.7:9999: connect: connection refused
2019/12/07 09:03:14 accept peer success
2019/12/07 09:03:15 connect peer success
#-------------------------output-------------------------

Run the following command in vpn2

create tun device with local ip 192.169.66.2
route packets with destination IP address 192.169.66.0/24 to tun device
create tcp tunnel with peer side(vpn2 10.0.2.6)

[root@vpn-2 /]$ ./vpn_linux_amd64 10.0.2.6 9999 192.169.66.2/24

#-------------------------output-------------------------
2019/12/07 09:03:14 tunIp='192.169.66.2'
2019/12/07 09:03:14 Tun Interface Name: tun0
2019/12/07 09:03:14 exec command 'ip address add 192.169.66.2 dev tun0'
2019/12/07 09:03:14 exec command 'ip link set dev tun0 up'
2019/12/07 09:03:14 exec command 'ip route add table main 192.169.66.0/24 dev tun0'
2019/12/07 09:03:14 non ipv4
2019/12/07 09:03:14 listener on '0.0.0.0:9999'
2019/12/07 09:03:14 try to connect peer
2019/12/07 09:03:14 connect peer success
2019/12/07 09:03:15 accept peer success
#-------------------------output-------------------------

We exec ping 192.169.66.2 -c 1 on vpn1(10.0.2.6)

[root@vpn-1 ~]$ ping 192.169.66.2 -c 1

#-------------------------output-------------------------
PING 192.169.66.2 (192.169.66.2) 56(84) bytes of data.
64 bytes from 192.169.66.2: icmp_seq=1 ttl=64 time=3.00 ms

--- 192.169.66.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 3.000/3.000/3.000/0.000 ms
#-------------------------output-------------------------

Here is the logs from machine vpn1

2019/12/07 09:04:11 receive from tun, send through tunnel IPFrame {
	version=4
	headerLen=5
	tos=0
	totalLen=84
	identification=17885
	flag=2
	offset=0
	ttl=64
	protocol=1
	headerCheckSum=61301
	source=192.169.66.1
	target=192.169.66.2
	payloadLen=64
}

2019/12/07 09:04:14 receive from tunnel, send through raw socketIPFrame {
	version=4
	headerLen=5
	tos=0
	totalLen=84
	identification=46327
	flag=0
	offset=0
	ttl=64
	protocol=1
	headerCheckSum=49243
	source=192.169.66.2
	target=192.169.66.1
	payloadLen=64
}

Here is the logs from machine vpn2

2019/12/07 09:04:12 receive from tunnel, send through raw socketIPFrame {
	version=4
	headerLen=5
	tos=0
	totalLen=84
	identification=17885
	flag=2
	offset=0
	ttl=64
	protocol=1
	headerCheckSum=61301
	source=192.169.66.1
	target=192.169.66.2
	payloadLen=64
}

2019/12/07 09:04:13 receive from tun, send through tunnel IPFrame {
	version=4
	headerLen=5
	tos=0
	totalLen=84
	identification=46327
	flag=0
	offset=0
	ttl=64
	protocol=1
	headerCheckSum=49243
	source=192.169.66.2
	target=192.169.66.1
	payloadLen=64
}

Icarus9913/vpn-demo

Compile

Run

Example