From c12283623a64544aaaab70f5cb21bd5741bb1754 Mon Sep 17 00:00:00 2001
From: Case Duckworth
Date: Thu, 7 May 2020 12:41:41 -0500
Subject: Version 0.3: add autossh support

Added autossh support. mrgrctrnl will default to using autossh if it's
installed; otherwise it'll do ssh in a while loop.

I did include 'ExitOnForwardFailure=yes' in my ~/.ssh/config, but I'm
thinking I should include that in __SSH_OPTIONS to be more robust. Might
be in 0.3.1 or whatever.

Another thing in 0.3.1 should be man pages and stuff. Maybe that'll be
0.4. I like version bumps.

CHANGES HERE (right, that's what this message is for):

- add autossh support: -S forces ssh ; -A forces autossh
- rewrite usage; add config file example
- change config file syntax (backward-compatible)
- add a few other commandline options
---
 mrgrctrnl | 198 +++++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 126 insertions(+), 72 deletions(-)

diff --git a/mrgrctrnl b/mrgrctrnl
index 796470c..b516596 100755
--- a/mrgrctrnl
+++ b/mrgrctrnl
@@ -1,126 +1,175 @@
 #!/bin/sh
 # mrgrctrnl: configurable ssh tunneler
 # Author: Case Duckworth <acdw@acdw.net>
-# Version: 0.2
+# Version: 0.3
 # License: MIT
 
 PRGN="${0##*/}"
 
-usage() {
-	cat <<END
-$PRGN: make magic ssh tunnels
-usage:	$PRGN [-h] [-k]
-	$PRGN [-n] [-c CONF | -s SSH]
-
-options:
-	-h	show this help
-	-k	kill all processes and exit
-	-r	restart $PRGN
-	-n	do a dry run: just print what would happen
-	-c CONFIG	use a different CONFIG file instead of
-			\$XDG_CONFIG_HOME/$PRGN/config
-	-s CMDLINE	directly input an ssh CMDLINE --
-			don't load the config file.
-END
-}
-
 # entry point
 main() {
+	# flags
+	_RUN=true
+	_LOG=true
+	_USE_CONFIG=true
+	# options
 	__CONFIG="${XDG_CONFIG_HOME:-$HOME/.config}/$PRGN/config"
-	__SSHCMD="-N \"\$user@\$machine\" -L \"\$local:\$remote\""
 	__PIDF="/tmp/$PRGN.pid"
-	_run=true
-	_quiet=false
-	_use_config=true
+	__CMDF="/tmp/$PRGN.cmd"
+	__SSH="$(command -v autossh || command -v ssh)"
+	__SSH_ARGS="-nT -N \"\$user@\$machine\" -L \"\$local:\$remote\""
 
-	while getopts hqkrnc:s: OPT; do
+	# save command invocation (for -r)
+	printf '%s %s\n' "$PRGN" "$*" >"$__CMDF"
+
+	# parse options
+	while getopts hkrnqSAc:s: OPT; do
 		case "$OPT" in
 		h)
 			usage
 			exit 0
 			;;
-		q) _quiet=true ;;
 		k)
-			tear_down
+			untunnel
 			pkill -x "$PRGN"
-			exit
+			exit "$?"
 			;;
 		r)
-			tear_down
-			exec "$PRGN"
+			untunnel
+			exec "$(cat "$__CMDF")"
 			;;
-		n) _run=false ;;
+		n) _RUN=false ;;
+		q) _LOG=false ;;
+		S) __SSH='ssh' ;;
+		A) __SSH='autossh' ;;
 		c) __CONFIG="$OPTARG" ;;
 		s)
-			__SSHCMD="$OPTARG"
-			_use_config=false
-			;;
-		*)
-			usage
-			exit 1
+			__SSH_ARGS="$OPTARG"
+			_USE_CONFIG=false
 			;;
+		*) exit 4 ;;
 		esac
 	done
+	shift $((OPTIND - 1))
 
-	if $_use_config && [ ! -r "$__CONFIG" ]; then
-		echo "!! $PRGN: Cannot find config file '$__CONFIG'."
-		echo "Aborting."
+	# make sure ssh is installed
+	if ! command -v "$__SSH" >/dev/null; then
+		log "Not installed: $__SSH"
 		exit 2
 	fi
 
-	if $_use_config; then
+	# make sure the config is readable
+	if $_USE_CONFIG && [ ! -r "$__CONFIG" ]; then
+		log "Cannot find config file $__CONFIG; aborting."
+		exit 3
+	fi
+
+	# load the config
+	if $_USE_CONFIG; then
 		awk '{sub(/#.*$/,"");print}' "$__CONFIG" |
 			while read -r machine user local remote key rest; do
-				if [ -z "$machine" ] || [ -z "$user" ] ||
-					[ -z "$local" ] || [ -z "$remote" ]; then
+				if [ -z "$machine" ] ||
+					[ -z "$user" ] ||
+					[ -z "$local" ] ||
+					[ -z "$remote" ]; then
 					continue
 				fi
 
+				case "$local" in
+				:*) local="localhost$local" ;;
+				esac
+				case "$remote" in
+				:*) remote="localhost$remote" ;;
+				esac
+
 				# shellcheck disable=2030
 				if [ -n "$key" ]; then
-					__SSHCMD="$__SSHCMD -i \"$key\""
+					__SSH_ARGS="$__SSH_ARGS -i \"$key\""
 				fi
 				if [ -n "$rest" ]; then
-					__SSHCMD="$__SSHCMD $rest"
+					__SSH_ARGS="$__SSH_ARGS $rest"
 				fi
 
-				eval "tunnel $__SSHCMD" &
+				eval "tunnel_${__SSH##*/} $__SSH_ARGS" &
 			done
 	else
-		# shellcheck disable=2031
-		eval "tunnel $__SSHCMD" &
+		#shellcheck disable=2031
+		eval "tunnel_${__SSH##*/} $__SSH_ARGS" &
 	fi
 
 	wait
 }
 
-tunnel() {
-	# shellcheck disable=2086
-	$_quiet || echo ssh "$@"
-	$_run && {
-		touch "$__PIDF"
-		while [ -e "$__PIDF" ]; do
-			grep -q -e "$*" "$__PIDF" && {
-				sleep 3
-				continue
-			}
-			# shellcheck disable=2015
-			if ssh "$@" & then
-				printf '%s\t%s\n' "$!" "$*" >>"$__PIDF"
-			else
-				badpid="$!"
-				kill "$badpid"
-				sed "/^$badpid/d" "$__PIDF" >"$__PIDF~" &&
-					mv "$__PIDF~" "$__PIDF"
-				continue
-			fi
+usage() {
+	cat <<END
+$PRGN: make magic ssh tunnels
+usage:	$PRGN [-h] [-k] [-r]
+	$PRGN [-n] [-q] [-S|-A] [-c FILE | -s ARGS]
+
+options:
+	-h	show this help
+	-k	demolish all tunnels and exit
+	-r	demolish all tunnels and restart
+	-n	dry run: just print what would happen
+	-q	quiet: don't print anything
+
+	-S	force use of 'ssh'
+	-A	force use of 'autossh'
+		default: use 'autossh' if installed, otherwise 'ssh'
+
+	-c FILE	load FILE as config file
+		default:	\$XDG_CONFIG_HOME/$PRGN/config
+
+	-s ARGS	run CMD with ARGS, do not read config file
+		default:	'-N USER@MACHINE -L LOCAL:REMOTE'
+				(populated from config file)
+
+config example:
+	# a hash mark comments to the end of the line
+	# if either 'local' or 'remote' begin with a colon,
+	# they'll be prefixed with 'localhost'
+	# machine	user	local	remote	key	other
+	example.com	bill	:1299	:6667	# key and other are optional
+END
+}
+
+tunnel_ssh() {
+	set -- ssh "$@"
+	log "$@"
+	$_RUN || return
+
+	touch "$__PIDF"
+	while [ -e "$__PIDF" ]; do # quit if the pid file is removed
+		# make sure we haven't tunneled this connection already
+		if grep -q -e "$*" "$__PIDF"; then
 			sleep 3
-		done
-	}
+			continue
+		fi
+
+		# try to start ssh tunnel
+		if "$@" & then
+			printf '%s\t%s\n' "$!" "$*" >>"$__PIDF"
+		else
+			badpid="$!"
+			kill "$badpid"
+			sed "/^$badpid/d" "$__PIDF" >"$__PIDF~" &&
+				mv "$__PIDF~" "$__PIDF"
+			continue
+		fi
+		sleep 3
+	done
 }
 
-tear_down() {
-	printf '%s...' "Killing extant tunnels"
+tunnel_autossh() {
+	set -- autossh -f "$@"
+	log "$@"
+	$_RUN || return
+
+	"$@" && printf '%s\t%s\n' "$!" "$*" >"$__PIDF"
+}
+
+untunnel() {
+	log "Killing tunnels"
 	if [ -e "$__PIDF" ]; then
 		while read -r pid _; do
 			kill "$pid" 2>/dev/null
@@ -128,8 +177,13 @@ tear_down() {
 		rm "$__PIDF"
 	else
 		pkill -x ssh
+		pkill -x autossh
 	fi
-	echo Done.
+	log "Done"
+}
+
+log() {
+	$_LOG && printf '%s: %s\n' "$PRGN" "$*" >&2
 }
 
 main "$@"
-- 
cgit 1.4.1-21-gabe81