From b4463d1e1bfd7d54451005aff0f6ae1f649042d1 Mon Sep 17 00:00:00 2001
From: Ian Kelling <ian@iankelling.org>
Date: Sun, 22 Jan 2017 12:40:11 -0800
Subject: [PATCH] add option to pick static network

---
 newns | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/newns b/newns
index dbe6598..2896cf2 100755
--- a/newns
+++ b/newns
@@ -38,21 +38,20 @@ fi
 usage() {
     cat <<EOF
 usage: ${0##*/} [OPTS] start|stop NS_NAME
-Setup & optionally create, a network namespace with nat and a mount namespace
+Nat a network namespace. create a mount ns. systemd friendly
 
 -c, --create    Create a named network namespace. When running from
                 the same network namespace as pid 1, this is set automatically.
                 This is the case when running outside a systemd created
                 private network.
+-n NETWORK      x.x.x /24 private network to use. If not specified, uses
+                the first one starting at 10.173.1
 -h, --help      Show this help and exit.
 
 From within a systemd network namespace, nat it to the outside. This
 would be called from ExecStartPre, and or subsequent units called with
 JoinsNamespaceOf= and PrivateNetwork=true.
 
-Uses /24 network, finding the first locally unused one starting at
-10.173.0.
-
 Also create a named mount namespace under /root/mount_namespaces, so we
 can alter some system config for this namespace. Subsequent systemd
 command lines would be prefixed with:
@@ -76,7 +75,7 @@ Background:
 This script does not make the namespace be named like ip does, because
 the naming is not necessary, although it could have been done with some
 more work. For debugging and joining the namespace with a bash shell, I
-use nsenter -n -m -t $(pgrep PROCESS_IN_NAMESPACE) bash.  Note: if I
+use nsenter -n -m -t \$(pgrep PROCESS_IN_NAMESPACE) bash.  Note: if I
 knew how to easily ask systemd what pid a unit has, i would do that.
 
 "ip netns new ..." also does a mount namespace, then bind
@@ -95,11 +94,12 @@ EOF
 
 #### begin arg parsing ####
 create=false
-temp=$(getopt -l help,create hc "$@") || usage 1
+temp=$(getopt -l help,create hcn: "$@") || usage 1
 eval set -- "$temp"
 while true; do
     case $1 in
         -c|--create) create=true; shift ;;
+        -n) network=$2; shift 2 ;;
         -h|--help) usage ;;
         --) shift; break ;;
         *) echo "$0: Internal error!" ; exit 1 ;;
@@ -162,10 +162,13 @@ nat() { dexec iptables -t nat $1 POSTROUTING -o $gateway_if -j MASQUERADE \
               -m comment --comment "systemd network namespace nat"; }
 
 find_network() {
+    if [[ $network ]]; then
+        return
+    fi
     found=false
     existing=false
     ips="$(ipd addr show | awk '$1 == "inet" {print $2}')"
-    for ((i=0; i <= 254; i++)); do
+    for ((i=1; i <= 254; i++)); do
         network=$ip_base.$i
         if printf "%s\n" "$ips" | grep "^${network//./\\.}" >/dev/null; then
             existing=true
-- 
2.30.2