ssh-and-tmux: add mosh support & tidy up the script

1 files changed, 60 insertions, 21 deletions

diff --git a/bin/ssh-and-tmux b/bin/ssh-and-tmux
index 6f1d482e..1aca3efc 100755
--- a/bin/ssh-and-tmux
+++ b/bin/ssh-and-tmux
@@ -1,18 +1,41 @@
 #!/bin/bash
 
-# when mosh isn't installed on the server, but tmux is, use this to get a
-# fairly persistent set of remote shell sessions.  I used to use autossh here,
-# but that means surprise dialogs asking to authorise use of an SSH key;
-# instead, just hit <Ret> to restart a window's connection when it's
-# convenient
+# Copyright (C) 2020-2022  Sean Whitton
 #
-# (The reason that I get prompted is because I have a short
-# ServerAliveInterval and low ServerAliveCountMax, but that's desirable,
-# because unresponsive SSH sessions are a massive pain)
+# 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 3 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, see <http://www.gnu.org/licenses/>.
 
-getopt=$(getopt -s bash -o "" -l 'container-cmd:,container-name:' -n ssh-and-tmux -- "$@")
-eval "set - $getopt"
 
+
+# Launcher for connections to remote persistent shell sessions, via mosh or a
+# mechanism for manual, but convenient, user-triggered reconnects.
+#
+# Advantage of the latter over autossh is avoidance of surprise dialogs asking
+# to authorise the use of SSH keys.  And thus works better than autossh with
+# short ServerAliveInterval and low ServerAliveCountMax ssh client config,
+# which are desirable for interactive sessions.
+
+
+
+# Space-separated list of hosts I want to mosh to.  Be conservative: it's not
+# just that mosh is available on that machine and it's not a highly
+# security-sensitive machine, but also that, e.g., the host reboots less often
+# than the workstation that'll be connecting, to avoid zombie clients.
+mosh_hosts="athena.silentflame.com"
+
+getopt=$(getopt -s bash -o "" \
+		-l 'container-cmd:,container-name:' -n ssh-and-tmux -- "$@")
+eval "set - $getopt"
 while true; do
     case "$1" in
 	'--container-cmd') container_cmd=$2; shift 2; continue ;;
@@ -21,26 +44,42 @@ while true; do
 	'--') shift; break ;;
     esac
 done
-
 host="$1"
 session="${2:-default}"
+if printf '%s\0' "${mosh_hosts[@]}" \
+	| grep -Fxqz "$host"; then use_mosh=true; else use_mosh=false; fi
+
 # Go via a login shell such that if there is no root tmux daemon yet, it ends
 # up with a PATH as though the first tmux session were launched from an
 # interactive shell.  This affects launching programs directly from tmux
 # (e.g. my C-\ e binding) for *all* sessions.
-cmd="\$SHELL -l -c \"tmux new-session -A -c \$HOME -s $session\""
+#
+# mosh does execvp directly so for simplicity we assume remote SHELL is bash.
+cmd="tmux new-session -A -c \$HOME -s $session"
+if $use_mosh; then
+    cmd=(bash -l -c "$cmd")
+else
+    cmd=(\$SHELL -l -c "\"$cmd\"")
+fi
+
 if [ -n "$container_name" ]; then
     display_host="$container_name"
-    cmd="$(printf "$container_cmd" "$container_name") -- $cmd"
+    cmd=($(printf "$container_cmd" "$container_name") -- "${cmd[@]}")
 else
     display_host="$host"
 fi
-echo -ne "\033]0;tmux $session on $display_host\007"
-prompt="Press any key to reconnect to tmux session $session on $display_host; d/C-d/C-c to give up .."
 
-while true; do
-    ssh -t "$host" "$cmd"
-    clear
-    read -n 1 -r -s -p "$prompt" ch
-    [ "$ch" = $'\04' -o "$ch" = d ] && echo && exit
-done
+if $use_mosh; then
+    mosh "$host" -- "${cmd[@]}"
+else
+    echo -ne "\033]0;tmux $session on $display_host\007"
+    prompt="Press any key to reconnect to tmux session $session on "
+    prompt+="$display_host; d/C-d/C-c to give up .."
+
+    while true; do
+	ssh -t "$host" "${cmd[*]}"
+	clear
+	read -n 1 -r -s -p "$prompt" ch
+	[ "$ch" = $'\04' -o "$ch" = d ] && echo && exit
+    done
+fi