From 350c783240fdb2f34e943ee71f321ce7b15114c3 Mon Sep 17 00:00:00 2001
From: Erich Eckner <git@eckner.net>
Date: Sat, 9 Feb 2019 23:07:39 +0100
Subject: backup.in: autodetect ipv4/6

---
 backup.in | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 56 insertions(+), 4 deletions(-)

diff --git a/backup.in b/backup.in
index b6d87b7..ca4c1ae 100755
--- a/backup.in
+++ b/backup.in
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-rsyncOptions='-6vxcaHAXF'
+rsyncOptions='-vxcaHAXF'
 rsync --help | \
   grep -q -- --may-modify-others && \
   rsyncOptions="${rsyncOptions} --may-modify-others"
@@ -27,6 +27,34 @@ Options:
   exit $1
 }
 
+extract_ssh_host() {
+  {
+    printf '%s\n' "$1"
+    if [ -f ~/.ssh/config ]; then
+      sed '
+        /^Host\s\+'"$1"'$/,/^Host\s/ {
+          s/^\s*Hostname\s\+//
+          t
+        }
+        d
+      ' ~/.ssh/config
+    fi
+  } \
+    | tail -n1
+}
+
+extract_ssh_ip_protocols() {
+  getent ahosts "$(extract_ssh_host "$1")" \
+    | sed '
+      s/^\([0-9]\+\.\)\{3\}[0-9]\+\s\+STREAM\(\s.*\)\?$/4/
+      t
+      s/^[0-9a-f][0-9a-f:]\+\s\+STREAM\(\s.*\)\?$/6/
+      t
+      d
+    ' \
+    | sort -u
+}
+
 if [ $# -eq 1 ]; then
   if [ "$1" == "--help" ]; then
     usage 0
@@ -57,17 +85,41 @@ QuellIP=$(echo "$3" | sed "s|^[a-zA-Z]*://||; s|^[a-zA-Z]*@||; s|:\?/.*$||")
 
 if [ "$#" -eq 3 ]; then
   Quelle="$3"
+  ipVer=$(
+    extract_ssh_ip_protocols "${QuellIP}" \
+      | sort -n \
+      | tail -n1
+  )
 elif [ "$#" -eq 4 ]; then
   sshHopp="$4"
   lokPort=$[$RANDOM/2+8000]
-  rsyncShell="-e ssh -6 -p${lokPort} -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null"
-  tunnelBefehl="ssh -6 -t -t -L[::1]:${lokPort}:${QuellIP}:22 ${sshHopp}"
   HoppIP="${sshHopp#*@}"
-  Quelle="$(echo "$3" | sed "s|${QuellIP}|[::1]|")"
+  ipVer=$(
+    {
+      extract_ssh_ip_protocols "${QuellIP}"
+      extract_ssh_ip_protocols "${HoppIP}"
+    } \
+      | sort -n \
+      | uniq -d \
+      | tail -n1
+  )
+  if [ ${ipVer} -eq 4 ]; then
+    localAddress='127.0.0.1'
+  elif [ ${ipVer} -eq 6 ]; then
+    localAddress='[::1]'
+  else
+    >&2 echo 'ip version of hopp and target must be the same'
+    exit 1
+  fi
+  rsyncShell="-e ssh -${ipVer} -p${lokPort} -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null"
+  tunnelBefehl="ssh -${ipVer} -t -t -L${localAddress}:${lokPort}:${QuellIP}:22 ${sshHopp}"
+  Quelle="$(echo "$3" | sed "s|${QuellIP}|${localAddress}|")"
 else
   usage
 fi
 
+rsyncOptions="${rsyncOptions}${ipVer}"
+
 if [ ! -d ${Basis} ]; then
   for neededMount in "${neededMounts[@]}"; do
     if ! mountpoint -q "${neededMount}"; then
-- 
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