fwdbak.sh

#!/bin/sh

#
# Tries to keep SSH-forwarding connection open for port forwarding
# using given range of local ports.
#

UserHost='SPECIFY_USER@HOST.HERE'

PortMin=20200
PortMax=20222
AliveChkSec=17
AliveChkCnt=3

Port="$PortMin"
while :; do
	ssh							\
		-o UserKnownHostsFile=/dev/null			\
		-o StrictHostKeyChecking=no			\
		-o ServerAliveInterval="$AliveChkSec"		\
		-o ServerAliveCountMax="$AliveChkCnt"		\
		-o ExitOnForwardFailure=yes			\
		-C -R"$Port":127.0.0.1:22			\
		"$UserHost"

	Port=$(($Port+1))
	if [ "$Port" -gt "$PortMax" ]; then
		Port="$PortMin"
	fi
done