transmission-daemon

# Username/password example
# DAEMON_ARGS="-b -t -a \"*.*.*.*\" -e /var/log/transmission/transmission.log"

# No username/password, but limited to 192.168.1.*
# DAEMON_ARGS="-b -T -a \"192.168.1.*\" -e /var/log/transmission/transmission.log"

INTERFACE=ppp0

if ifconfig $INTERFACE >>/dev/null 2>&1; then
    BIND_ADDR="`/sbin/ifconfig $INTERFACE | awk '$1 == \"inet\" {print $2}' | awk -F: '{print $2}'`"
else
    BIND_ADDR="127.0.0.1"
fi

DAEMON_ARGS="--bind-address-ipv4 $BIND_ADDR"

iptables -t nat -A PREROUTING -p tcp --dport 51413 -j DNAT --to-destination {BIND_ADDRESS}:51413
iptables -t nat -A PREROUTING -p upd --dport 51413 -j DNAT --to-destination {BIND_ADDRESS}:51413

-i tap+