FS#3830 - OpenVPN Client Using TCP Connection Has MTU or TCPMSS Issue

[openwrt-bot]

weikai:

OpenVPN Client connects to a TCP based OpenVPN server connects fine. However, the connections to remote network servers connect but can't transfer data. The mangle rule with clamp-mss-to-pmtu won't receive any data. Setting tcpmss to something around 1000 will only receive the first 100 - 200 bytes and hang. It's not working until reduced tcpmss to 59.

iptables -t nat -A postrouting_rule -o tun0 -j MASQUERADE
iptables -t mangle -A POSTROUTING -o tun0 -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 59
#iptables -t mangle -A POSTROUTING -o tun0 -p tcp -m tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu