#!/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 #

# $ ksh sshnfs.ksh -o NFSURL=nfs://derfwpc5131/export/home/rmainz -o NFSJumphost=rmainz@derfwpc5131,roland.mainz@derfwnb8353 -J rmainz@derfwpc5131,roland.mainz@derfwnb8353 root@10.49.20.207

# $ ksh sshnfs.ksh -o NFSURL=nfs://derfwpc5131/export/home/rmainz target@fe80::d6f5:27ff:fe2b:8588%enp2s0

#

# Written by Roland Mainz <roland.mainz@nrubsig.org>

#

#

# simple netstat -n parser

#

function netstat_list_connections

{

	set -o nounset

	nameref data=$1

	compound out=( typeset stdout stderr ; integer res )

	out.stderr="${ { out.stdout="${ LC_ALL='POSIX' PATH='/usr/bin:/bin' netstat -a -n ; (( out.res=$? )) ; }" ; } 2>&1 ; }"

	if (( out.res != 0 )) || [[ ${out.stderr} != '' ]] ; then

		return 1

	fi

	typeset -a data.connections

	typeset l

	integer dci=0 # data.connections array index

	while read l ; do

		leftover="${l/~(Elrx)

		(?: # non-capturing group

			#

			# regex group for tcp,udp

			#

			[[:space:]]+

			([[:digit:]]+)			# Recv-Q

			[[:space:]]+

			([[:digit:]]+)			# Send-Q

			[[:space:]]+

			([^[:space:]]+)			# Local Address

			[[:space:]]+

			([^[:space:]]+)			# Foreign Address

			(?:

				|

				[[:space:]]+

				([^[:space:]]*?) 	# State (Optional)

			)

		|

			#

			# regex for unix

			#

			(unix)				# Proto

			[[:space:]]+

			([[:digit:]]+)			# RefCnt

			[[:space:]]+

			(\[.+?\])			# Flags

			[[:space:]]+

			([^[:space:]]+) 		# Type

			[[:space:]]+

			([^[:space:]]*?)		# State (optional)

			[[:space:]]+

			([[:digit:]]+)			# I-Node

			(?:

				|

				[[:space:]]+

				([^[:space:]]+)		# Path (optional)

			)

		)

			/X}"

		# If the regex above did not match then .sh.match

		# remains untouched, so we might see data from the

		# previous round.

		# So we check the "leftover" var whether it just

		# contains the dummy value of "X" to indicate a

		# successful regex match

		if [[ "$leftover" == 'X' ]] ; then

			#print -v .sh.match

			if [[ "${.sh.match[1]-}" != '' ]] ; then

				nameref dcn=data.connections[$dci]

				typeset dcn.proto="${.sh.match[1]}"

				typeset dcn.recv_q="${.sh.match[2]}"

				typeset dcn.send_q="${.sh.match[3]}"

				typeset dcn.local_address="${.sh.match[4]}"

				typeset dcn.foreign_address="${.sh.match[5]}"

				typeset dcn.state="${.sh.match[6]}"

				((dci++))

			elif [[ "${.sh.match[7]-}" != '' ]] ; then

				nameref dcn=data.connections[$dci]

				typeset dcn.proto="${.sh.match[7]}"

				typeset dcn.refcnt="${.sh.match[8]}"

				typeset dcn.flags="${.sh.match[9]}"

				typeset dcn.type="${.sh.match[10]}"

				[[ "${.sh.match[11]}" != '' ]] && typeset dcn.state="${.sh.match[11]}"

				typeset dcn.inode="${.sh.match[12]}"

				[[ "${.sh.match[13]}" != '' ]] && typeset dcn.path="${.sh.match[13]}"

				((dci++))

			fi

		else

			true

			#printf $"leftover=%q\n" "${leftover}"

		fi

	done <<<"${out.stdout}"

	return 0

}

function netstat_list_active_local_tcp_connections

{

	set -o nounset

	nameref ar=$1

	compound c

	integer port

	integer i

	netstat_list_connections c || return 1

	#print -v c

	[[ -v ar ]] || integer -a ar

	for i in "${!c.connections[@]}" ; do

		nameref n=c.connections[$i]

		# look for only for TCP connections which match

		# 127.0.*.* or IPv6 ::1 for localhost

		# 0.0.0.0 or IPv6 :: for all addresses (e.g. servers)

		if [[ "${n.proto}" == ~(El)tcp && \

			"${n.local_address}" == ~(Elr)((127\.0\..+|::1)|(::|0\.0\.0\.0|)):[[:digit:]]+ ]] ; then

			port="${n.local_address##*:}"

			#printf $"port = %d\n" port

			(( ar[port]=1 ))

		fi

	done

	return 0

}

function netstat_find_next_free_local_tcp_port

{

	set -o nounset

	compound c=( integer -a ar )

	nameref ret_free_port=$1

	integer start_port

	integer end_port

	integer i

	netstat_list_active_local_tcp_connections c.ar || return 1

	#print -v c

	(( start_port=$2 ))

	if (( $# > 2 )) ; then

		(( end_port=$3 ))

	else

		(( end_port=65535 ))

	fi

	for ((i=start_port ; i < end_port ; i++ )) ; do

		if [[ ! -v c.ar[i] ]] ; then

			(( ret_free_port=i ))

			return 0

		fi

	done

	return 1

}

#

# 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]}"

	[[ "${.sh.match[3]}" != '' ]] && integer data.port="${.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

{

	set -o nounset

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

	integer i

	integer retval

	compound c=(

		# port on THIS machine

		integer local_forward_port

		# TCP port on destination machine where we forward the

		# NFS port from the server

		integer destination_nfs_port=33049

		typeset ssh_control_socket_name="/tmp/sshnfs_ssh-control-socket_logname${LOGNAME}_ppid${PPID}_pid$$"

	)

	#

	# find free local forwarding port...

	#

	(( i=34049 ))

	netstat_find_next_free_local_tcp_port c.local_forward_port $i

	#

	# ... and adjust c.destination_nfs_port by the same offset

	# we do that so that multiple sshweb.ksh logins to the same

	# machine do try to use the same ports on that machine

	#

	(( c.destination_nfs_port += c.local_forward_port-i ))

	${mydebug} && printf $"debug: c.local_forward_port=%d, c.destination_nfs_port=%d\n" \

		c.local_forward_port \

		c.destination_nfs_port

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

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

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

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

					((i++))

					;;