MBCDN

IPTables Regeln.

iptables -t mangle -N DIVERT
iptables -t mangle -A PREROUTING -p tcp -m socket -j DIVERT
iptables -t mangle -A DIVERT -j MARK --set-mark 1
iptables -t mangle -A DIVERT -j ACCEPT

iptables -t mangle -A PREROUTING -p tcp --dport 25 -j TPROXY --tproxy-mark 0x1/0x1 --on-port 25

Policy Routing.

ip rule add fwmark 1 lookup 100
ip route add local 0.0.0.0/0 dev lo table 100

In /etc/sysctl.conf aktivieren.

echo 1 > /proc/sys/net/ipv4/ip_nonlocal_bind