ansible: gsm-tester: Enable ip forwarding and masquerading on boot

Some nodes in the internal network, such as LimeNetMicro, will need
Internet access to upgrade osmo-trx-lms from OBS repos.
It also makes it easier to update manually other nodes inside the
internal network.

Change-Id: I2c89cf9cfcb55b3153e7be212c68ffa8db0f6927

ansible/roles/gsm-tester-network/README.md

@@ -4,4 +4,5 @@ The network configuration is not set by default.
 
 # variables
 
-- `bts_interface` (eth1): on which network interface the bts is configured.
+- `bts_interface` (enp2s0): on which network interface the bts is configured.
+- `gw_interface` (enp1s0): on which network interface the traffic is routed towards default gateway.

ansible/roles/gsm-tester-network/defaults/main.yml

@@ -1,3 +1,4 @@
 ---
 
-bts_interface: eth1
+bts_interface: enp2s0
+gw_interface: enp1s0

ansible/roles/gsm-tester-network/files/ogt-sysctl.conf

@@ -0,0 +1 @@
+net.ipv4.ip_forward=1

ansible/roles/gsm-tester-network/tasks/main.yml

@@ -9,3 +9,15 @@
 - name: start all network interface
   command: ifup -a
   when: gsm_tester_network_interface is changed
+
+- name: allow ip forwarding and masquerading traffic from internal network (iptables)
+  template:
+    src: etc/iptables-ogt
+    dest: /etc/network/if-up.d/iptables-ogt
+    mode: 0755
+
+- name: allow ip forwarding from internal network (sysctl)
+  copy:
+    src: ogt-sysctl.conf
+    dest: /etc/sysctl.d
+  notify: restart udev

ansible/roles/gsm-tester-network/templates/etc/iptables-ogt

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+IPT="/sbin/iptables"
+
+if [ "$IFACE" = "{{ gw_interface }}" ]; then
+  # Apply masquerading if not yet applied:
+  if [ "x$($IPT -t nat -S | grep "\-A POSTROUTING -o {{ gw_interface }} -j MASQUERADE" -c)" = "x0" ]; then
+        $IPT -t nat -A POSTROUTING -o {{ gw_interface }} -j MASQUERADE
+  fi
+
+  # Allow IP forwarding if not yet enabled:
+  if [ "x$($IPT -t filter -S | grep "\-A FORWARD -j ACCEPT" -c)" = "x0" ]; then
+    $IPT -t filter -A FORWARD -j ACCEPT
+  fi
+
+  echo "osmo-gsm-tester iptables rules loaded."
+fi