sshnfs - ssh with nfs forwarding
Posted by Anonymous on Wed 8th Feb 2023 14:54
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#!/usr/bin/ksh93
#
# sshnfs - remote login client with NFSv4 forwarding
#
# Example usage:
# $ ksh sshnfs.ksh nfs://localhost/export/home/rmainz root@10.49.20.207 #
#
# Written by Roland Mainz <roland.mainz@nrubsig.org>
#

#
# 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" "$0" ; return 1 ; }
        [[ "${data.host}" != '' ]]              || { print -u2 -f $"%s: NFS hostname missing\n" "$0" ; return 1 ; }
        [[ "${data.path}" != '' ]]              || { print -u2 -f $"%s: NFS path missing\n" "$0" ; return 1 ; }

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

        return 0
}


function main
{
        integer i
        compound c
        compound c.nfs_data
        integer c.forward_port=4049

        set -o xtrace
        set -o nounset

        url="$1" # fixme: we should use sshnfs -o NFSURL=nfs:// ...
        shift
        typeset c.args=( "$@" )

        parse_nfs_url c.nfs_data "$url" || return 1

        #
        # extract jump host args
        #
        typeset -a c.ssh_jumphost_args
        for ((i=0 ; i < ${#c.args[@]} ; i++)) ; do
                if [[ "${c.args[i]}" == '-o' ]] ; then
                        if [[ "${c.args[i+1]}" == ~(Elr)NFSJumphost=.+ ]] ; then
                                c.ssh_jumphost_args+=( "-J" "${c.args[i+1]#NFSJumphost=}" )
                                unset c.args[$i]
                                unset c.args[$((i+1))]
                        fi
                fi
        done

        # Forward NFS port from server to local machine
        # Notes:
        # - We use $ ssh -M ... # here as a way to terminate the port
        # forwarding process later using "-O exit" without the need
        # for a pid
        printf $"# Please enter the password for NFS server (%s)\n" \
                "root@${c.nfs_data.host}"
        ssh \
                -L "${c.forward_port}:localhost:${c.nfs_data.port}" \
                -M -S "$PWD/ssh-control-socket" \
                -N \
                -f -o ExitOnForwardFailure=yes \
                "${c.ssh_jumphost_args[@]}" \
                "root@${c.nfs_data.host}"
        (( $? == 0 )) || { printf $"%s: NFS forwarding ssh failed with error code %d\n" "$0" $? ; return 1 ; }
        #ssh -S "$PWD/ssh-control-socket" -O 'check' "root@${c.nfs_data.host}"

        printf $"# Use this to mount the directory:\n"
        printf $"# $ mkdir /mnt_nfs\n"
        printf $"# mount -vvv -t nfs -o vers=4,port=%d localhost:/%s /mnt_nfs\n" \
                3049 \
                "${c.nfs_data.path}"

        ssh -R "3049:localhost:${c.forward_port}" "${c.args[@]}" # root@10.49.20.207

        ssh -S "$PWD/ssh-control-socket" -O 'exit' "root@${c.nfs_data.host}"
        wait

        return 0
}

main "$@"

# EOF.