udp2raw openvpn config guide
./udp2raw_amd64 -s -l0.0.0.0:8855 -r 127.0.0.1:7777 -k "passwd" --raw-mode faketcp -a
assume server ip is 45.66.77.88
./udp2raw_amd64 -c -l0.0.0.0:3333 -r 45.66.77.88:8855 -k "passwd" --raw-mode faketcp -a
You can add --cipher-mode xor --auth-mode simple to both sides to obtain maximum performance(but poor security).
client
dev tun100
proto udp
remote 127.0.0.1 3333
resolv-retry infinite
nobind
persist-key
persist-tun
ca /root/add-on/openvpn/ca.crt
cert /root/add-on/openvpn/client.crt
key /root/add-on/openvpn/client.key
keepalive 3 20
verb 3
mute 20
comp-lzo no #this option is deprecated since openvpn2.4. For 2.4 and above, use "compress" instead
#compress
cipher none ##### disable openvpn 's cipher and auth for maxmized peformance.
auth none ##### you can enable openvpn's cipher and auth,if you dont care about peformance,or you dont trust udp2raw 's encryption
fragment 1200 ##### very important it's a conservative value, you can turn it up a bit
mssfix 1200 ##### very important
sndbuf 2000000 ##### important
rcvbuf 2000000 ##### important
txqueuelen 4000 ##### suggested
local 0.0.0.0
port 7777
proto udp
dev tun
ca /etc/openvpn/easy-rsa/2.0/keys/ca.crt
cert /etc/openvpn/easy-rsa/2.0/keys/server.crt
key /etc/openvpn/easy-rsa/2.0/keys/server.key
dh /etc/openvpn/easy-rsa/2.0/keys/dh1024.pem
server 10.222.2.0 255.255.255.0
ifconfig 10.222.2.1 10.222.2.6
client-to-client
duplicate-cn
keepalive 10 60
max-clients 50
persist-key
persist-tun
status /etc/openvpn/openvpn-status.log
verb 3
mute 20
comp-lzo no #this option is deprecated since openvpn2.4. For 2.4 and above, use "compress" instead
#compress
cipher none ##### disable openvpn 's cipher and auth for maxmized peformance.
auth none ##### you can enable openvpn's cipher and auth,if you dont care about peformance,or you dont trust udp2raw 's encryption
fragment 1200 ##### very important it's a conservative value, you can turn it up a bit
mssfix 1200 ##### very important
sndbuf 2000000 ##### important
rcvbuf 2000000 ##### important
txqueuelen 4000 ##### suggested
Check this article,its same for udp2raw+OpenVPN :
https://github.com/wangyu-/UDPspeeder/wiki/UDPspeeder-openvpn-config-guide
If you want to transparently redirect traffic by VPN, it's very important to add a route exception (on client side) so that the VPN won't hijack udp2raw's traffic. Since your VPN traffic goes throught udp2raw, if your VPN hijacks udp2raw's traffic then there will be a traffic loop and your udp2raw will lost connection.
for the reason of a smaller MTU see https://github.com/wangyu-/udp2raw/wiki/about-mtu