sshnfs - ssh with nfs forwarding
Posted by Anonymous on Wed 8th Feb 2023 13:33
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#
# sshnfs - remote login client with NFSv4 forwarding
#

#
# parse url
#
# returns:
# data.protocol
# data.host
# data.port (optional)
# data.path
#
function parse_url
{
        typeset url="$2"
        typeset leftover
        nameref data="$1"

        leftover="${url//~(Elr)(.+?):\/\/(.+?)(?:|:([[:digit:]]+))(?:\/(.*?))?/x}"

        [[ "$leftover" == 'x' ]] || { print -u2 -f $"%s: Parser error\n" "$0" ; return 1 ; }

        #print -v .sh.match

        data.protocol="${.sh.match[1]}"
        data.host="${.sh.match[2]}"
        # bug: should be [[ -v .sh.match[3] }}, but ksh93u has bugs
        [[ "${.sh.match[3]}" != '' ]] && integer data.port="${.sh.match[3]}"
        data.path="${.sh.match[4]}"
        return 0
}

function parse_nfs_url
{
        typeset url="$2"
        nameref data="$1"

        parse_url data "$url" || return 1

        [[ "${data.protocol}" == 'nfs' ]] || { print -u2 -f $"%s: Not a NFS url\n" "$0" ; return 1 ; }

        if [[ ! -v data.port ]] ; then
                integer data.port=2049
        fi

        return 0
}


function main
{
        compound c
        compound c.nfs_data
        integer c.forward_port=4049
set -x
        url="$1"
        shift
        parse_nfs_url c.nfs_data "$url" || return 1

        # $ ssh -f ... # puts the ssh process into the bachground, but
        # we have no way to determinate the process id. The "fix" is
        # to start a new process, and then use exec(1) to re-use the
        # process id of the shell for that ssh process
        print -v c >"mydata"
        ksh -c 'set -o errexit -o xtrace ; read -C c <"mydata" ; printf "%d\n" $$ >"mypid" ; exec ssh -L "${c.forward_port}:localhost:${c.nfs_data.port}" -N -f -o ExitOnForwardFailure=yes "root@${c.nfs_data.host}"'
        (( $? == 0 )) || { printf $"%s: NFS forwarding ssh failed with error code %d\n" "$0" $? ; return 1 ; }
        (( c.forward_pid=$( <'mypid') ))
        #rm 'mypid'

        ssh -Y -R "3049:localhost:${c.forward_port}" root@10.49.20.207

        kill -s TERM "${c.forward_pid}"
        wait

        return 0
}

main "$@"

# EOF.