xvnc "-r" option: working solution!

Works around regression in xvncviewer where reverse connections no
longer work.  We now use direct connections for -r.  Also, we now
default to direct connections without '-r', since reverse connections
fail to forward mouse+keyboard.

The occupation of the port on both connection sides is not ideal.

Also note that this also shares the local desktop with all other local
users.  Limiting the port to the calling user would be a good security
feature!

This may be relevant:
https://serverfault.com/questions/127794/forward-local-port-or-socket-file-to-remote-socket-file/753733#753733

Not sure if either x11vnc or xvncviewer can use socket files.

1 files changed, 47 insertions, 3 deletions

diff --git a/dot/local/bin/xvnc b/dot/local/bin/xvnc
index 957fa2b..e1e99a1 100755
--- a/dot/local/bin/xvnc
+++ b/dot/local/bin/xvnc
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # x11vnc option '-noxrecord' added as workaround for crashing bug
 # See https://github.com/LibVNC/x11vnc/issues/61
@@ -40,6 +40,49 @@ reverse_connection()
     kill $pid
 }
 
+ssh()
+{
+    command ssh "$@" 2>&1 | sed 's/^/REMOTE> /'
+}
+
+share_display_direct()
+{
+    if [ "$DEBUG" ]
+    then
+        set -x
+    fi
+
+    port=5500
+    while fuser -vk $port/tcp
+    do
+        sleep 0.1
+    done
+    x11vnc -noxrecord -q -nopw -ncache -ncache_cr -localhost -display "${local_display}" -rfbport "$port" &
+    X11VNC=$!
+    trap 'if [ ! "$DEBUG" ]; then exec 2>/dev/null; fi; set -- "$X11VNC" "$SSH"; ps hu "$@"; kill "$@"' EXIT
+
+    while ! fuser -v $port/tcp
+    do
+        [ -e /proc/"$X11VNC" ] || break
+        sleep 0.1
+    done
+
+    # TODO: spin waiting for port 5500
+    ssh -n \
+        ${remote_port:+ -p "$remote_port" } \
+        "$remote_host" \
+        "fuser -vk $port/tcp && sleep 1"
+    ssh -n \
+        -o ControlPath=none \
+        -o ExitOnForwardFailure=yes \
+        -R "localhost:$port:localhost:$port" \
+        ${remote_port:+ -p "$remote_port" } \
+        "$remote_host" \
+        "DISPLAY=${remote_display} xvncviewer localhost:$port" 2>&1 &
+    SSH=$!
+    wait -n
+}
+
 share_display()
 {
     set -x
@@ -60,13 +103,14 @@ share_display()
 if [ "$1" = -r ]
 then
     shift
-    cmd=share_display
+    cmd=share_display_direct
 elif [ "$1" = -d ]
 then
     shift
     cmd=direct_connection
 else
-    cmd=reverse_connection
+    # cmd=reverse_connection
+    cmd=direct_connection
 fi
 
 remote_host=${1:-blackboard}