#!/usr/bin/ksh93

#

# sshnfs - remote login client with NFSv4 forwarding

#

# Example usage:

# $ ksh sshnfs.ksh -o NFSURL=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"

	# ~(E) is POSIX extended regular expression matching (instead of

	# shell pattern)

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

	# All parsed data should be captured via eregex in .sh.match - if

	# there is anything left (except the 'X') then the input string did not

	# properly match the eregex

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

	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

		# use # default NFSv4 TCP port number (see

		# $ getent services nfs #)

		integer data.port=2049

	fi

	return 0

}

function main

{

	integer i

	integer retval

	compound c=(

		# port on THIS machine

		integer local_forward_port=34049

		# TCP port on destination machine where we forward the

		# NFS port from the server

		integer destination_nfs_port=33049

		# fixme: "/tmp" vs. "${XDG_RUNTIME_DIR:-/tmp}" ?

		typeset ssh_control_socket_name="/tmp/sshnfs_ssh-control-socket_${LOGNAME}_${PPID}_$$"

	)

	#set -o xtrace

	typeset mydebug=false # fixme: should be "bool" for ksh93v

	set -o nounset

	typeset c.args=( "$@" )

	for ((i=0 ; i < ${#c.args[@]} ; i++)) ; do

		if [[ "${c.args[i]}" == '-o' ]] ; then

			case "${c.args[i+1]-}" in

				'NFSURL='*)

					unset c.nfs_server

					compound c.nfs_server

					typeset c.url="${c.args[i+1]#NFSURL=}"

					parse_nfs_url c.nfs_server "${c.url}" || return 1

					unset c.args[$i] c.args[$((i+1))]

					((i++))

					;;

				'NFSJumphost='*)

					[[ ! -v c.ssh_jumphost_args ]] && typeset -a c.ssh_jumphost_args

					c.ssh_jumphost_args+=( "-J" "${c.args[i+1]#NFSJumphost=}" )

					unset c.args[$i] c.args[$((i+1))]

					((i++))

					;;

			esac

		fi

	done

	if [[ -v c.nfs_server ]] ; then

		# 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

			"root@${c.nfs_server.host}"

		ssh \

			-L "${c.local_forward_port}:localhost:${c.nfs_server.port}" \

			-M -S "${c.ssh_control_socket_name}" \

			-N \

			-f -o 'ExitOnForwardFailure=yes' \

			"${c.ssh_jumphost_args[@]}" \

			"root@${c.nfs_server.host}"

		if (( $? != 0 )) ; then

			print -u2 -f $"%s: NFS forwarding ssh failed with error code %d\n" "$0" $?

			return 1

		fi

		# debug

		${mydebug} && ssh -S "${c.ssh_control_socket_name}" -O 'check' "root@${c.nfs_server.host}"

		print -u2 -f $"# Use this to mount the directory:\n"

		print -u2 -f $"# $ mkdir /mnt_nfs\n"

		print -u2 -f $"# $ mount -vvv -t nfs -o vers=4,port=%d localhost:/%s /mnt_nfs\n" \

			c.destination_nfs_port \

			"${c.nfs_server.path}"

		# add NFS forwarding options to main ssh argument list

		c.args=(

			'-R' "${c.destination_nfs_port}:localhost:${c.local_forward_port}"

			'-o' 'ExitOnForwardFailure=yes'

			"${c.args[@]}"

		)

	fi

	${mydebug} && print -v c

	ssh "${c.args[@]}" ; (( retval=$? ))

	if [[ -v c.nfs_server ]] ; then

		ssh -S "${c.ssh_control_socket_name}" -O 'exit' "root@${c.nfs_server.host}"

	fi

	wait

	return $retval

}

main "$@"

exit $?

# EOF.