ssh tuntap #017
Posted by Anonymous on Thu 14th Apr 2022 14:05
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#!/usr/bin/ksh93

#
# Ethernet/tap forwarding via ssh
#

set -o xtrace
set -o errexit
set -o nounset

# list of commands our ssh session should execute
typeset -a sshcmds=(
        #
        # cleanup:
        #
        # we need to clean up the bridge interface ourselves, if
        # we do not do that we risk getting that any subsequent
        # ifconfig/ip/etc command hangs
        #
        '(( trap_once=0 )) ;'
        "netcleanup() { "
                '(( trap_once++ > 0 )) && return 0 ;'
                "set +o errexit ;"
                "brctl delif br19 tap19 ;"
                "brctl delif br19 eno1 ;"
                "ifconfig tap19 down ;"
                "ifconfig br19 down ;"
                "brctl delbr br19 ;"
                "exit 0 ;"
        "} ;"
        'trap netcleanup EXIT ;'
        'trap netcleanup HUP ;'

        "set -o xtrace ;"
        "set -o errexit ;"
        "brctl addbr br19 ;"
        "brctl addif br19 tap19 ;"
        "brctl addif br19 eno1 ;"
        "brctl show ;"
        "ifconfig tap19 promisc ;"
        "ifconfig tap19 up ;"
        "ifconfig br19 up ;"

        "read dummy ;" # wait

        # this is tricky (and nasty):
        # we have to tell our session sshd instance to quit, and then
        # busy-wait until we get SIGHUP from gthat sshd process back
        # so our HUP trap handler function gets called
        'kill -s INT ${PPID} ;'
        'while true ; do sleep 0.1 ; done ;'
)

ssh \
        -o ExitOnForwardFailure=yes \
        -o PermitLocalCommand=yes \
        -o LocalCommand="ifconfig tap19 up" \
        -o Tunnel=ethernet -w 19:19 \
        root@10.49.20.202 \
        "${sshcmds[*]}"

# cleanup
# ...

# EOF.