From: Mark Wooding <mdw@distorted.org.uk>
Date: Sun, 19 Dec 2010 03:14:17 +0000 (+0000)
Subject: hacks/ssh: Add new hack for setting up background SSH master connections.
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/profile/commitdiff_plain/4d7d040beb835fa5ea0015d0e1202f61fa79c0c1

hacks/ssh: Add new hack for setting up background SSH master connections.

I don't really know why SSH doesn't do this by default; but it damned
well ought to.
---

diff --git a/hacks/ssh b/hacks/ssh
new file mode 100755
index 0000000..a11c777
--- /dev/null
+++ b/hacks/ssh
@@ -0,0 +1,172 @@
+#! /bin/bash
+###
+### SSH wrapper to spawn separate SSH master connections on demand
+###
+### (c) 2010 Mark Wooding
+###
+
+###----- Licensing notice ---------------------------------------------------
+###
+### This program is free software; you can redistribute it and/or modify
+### it under the terms of the GNU General Public License as published by
+### the Free Software Foundation; either version 2 of the License, or
+### (at your option) any later version.
+###
+### This program is distributed in the hope that it will be useful,
+### but WITHOUT ANY WARRANTY; without even the implied warranty of
+### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+### GNU General Public License for more details.
+###
+### You should have received a copy of the GNU General Public License
+### along with this program; if not, write to the Free Software Foundation,
+### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+###--------------------------------------------------------------------------
+### Configuration.
+
+: ${REAL_SSH=/usr/bin/ssh}
+
+###--------------------------------------------------------------------------
+### Parse the command line and dredge out information.
+
+## This is a reasonable approximation to SSH's command-line argument parser.
+unset host login
+mode=m
+declare -a opts masteropts
+while :; do
+  case "$1,$#" in
+
+    ## Nothing left.  We're done.
+    ,0)
+      break
+      ;;
+
+    ## A command line option group.  Parse it and work out what's going on.
+    -*)
+      opt=$1
+      opts=("${opts[@]}" "$opt")
+      while :; do
+
+	## Strip off the first character, because it's the one we dealt with
+	## last time.
+	opt=${opt#?}
+	o=$opt
+
+	## Phase 1: identify the option and whether it needs an argument.
+	unset arg
+	case "$o" in
+
+	  ## Empty group.  We're done.
+	  "")
+	    break
+	    ;;
+
+	  ## Options with arguments.
+	  [bcDeFiLlmOopRSw]*)
+	    case "$#,$o" in
+
+	      ## You're going to lose because there's no argument.  But we'll
+	      ## let SSH deal with that.
+	      1,?)
+		arg=
+		;;
+
+	      ## There's an argument cuddled on to the end of the option.  It
+	      ## will have been committed to the `opts' array as part of the
+	      ## option group.
+	      *,??*)
+		arg=${opt#?}
+		opt=
+		;;
+
+	      ## Nope.  There's an argument in the next word.  Grab it and
+	      ## commit it.
+	      *)
+		arg="$2"
+		opts=("${opts[@]}" "$arg")
+		shift
+		;;
+	    esac
+	    ;;
+
+	  ## Anything else.  Let it go even if it's not valid: SSH will moan
+	  ## if it wants.  Note that `--' is ignored by SSH, but this isn't
+	  ## documented; in particular, `--' is /not/ a POSIX end-of-options
+	  ## marker, so we don't try to handle it specially here either.
+	  *)
+	    ;;
+	esac
+
+	## Phase two.  Figure out whether what this means for us.
+	case "$mode,$o" in
+
+	  ## `-O foo' and `-S foo' mean that the caller wants to take
+	  ## control of the multiplexing process.
+	  ?,[MOS]*)
+	    mode=p
+	    ;;
+
+	  ## Catch the login name if there is one.  Make sure the master
+	  ## knows it.
+	  ?,l*)
+	    masteropts=("${masteropts[@]}" "-l$arg")
+	    login=$arg
+	    ;;
+
+	  ## These options are interesting to the master connection.
+	  m,[aADLlRSwxXv]*)
+	    masteropts=("${masteropts[@]}" "-${o:0:1}$arg")
+	    ;;
+
+	  ## SSH options on the command line merit special attention.  Pass
+	  ## them onto the master, if necessary.
+	  ?,o*)
+	    masteropts=("${masteropts[@]}" "${opt:0:1}$arg")
+	    case "$mode,$arg" in
+
+	      ## User wants to control the process.  Let him.
+	      ?,ControlMaster=* | ?,ControlPath=*)
+		mode=p
+		;;
+
+	    esac
+	    ;;
+	esac
+      done
+      ;;
+
+    ## A bare word.  Maybe it's the hostname, or the start of the command.
+    *)
+      case ${host-t} in
+	t) host=$1 ;;
+	*) break ;;
+      esac
+      ;;
+  esac
+  shift
+done
+
+###--------------------------------------------------------------------------
+### Now to actually do the job.
+
+## If there's no host, pass straight through.  We can't do anything useful
+## anyway.
+case ${host+t} in
+  t) ;;
+  *) mode=p ;;
+esac
+
+## Actually do something useful.
+case "$mode" in
+  p)
+    exec "$REAL_SSH" "${opts[@]}" ${host+"$host"} "$@"
+    ;;
+  m)
+    if ! "$REAL_SSH" -Ocheck ${login+"$login@"}"$host" >/dev/null 2>&1; then
+      "$REAL_SSH" -MNf "${masteropts[@]}" "$host"
+    fi
+    exec "$REAL_SSH" ${opts[@]} "$host" "$@"
+    ;;
+esac
+
+###----- That's all, folks --------------------------------------------------
diff --git a/setup b/setup
index 76b95db..5e55c9b 100755
--- a/setup
+++ b/setup
@@ -248,6 +248,19 @@ for s in $scripts; do
 done
 echo "	all done."
 
+hacks="
+  ssh:ssh"
+echo "Installing hacks..."
+for h in $hacks; do
+  d=${h%%:*} h=${h#*:}
+  ft=$HOME$sub/bin/hacks/$d
+  mkdir -p $ft
+  ln -s $here/hacks/$h $ft/$h.new
+  mv $ft/$h.new $ft/$h
+  echo "  $d:$h"
+done
+echo "	all done."
+
 ###--------------------------------------------------------------------------
 ### Set up the Emacs config.