From 6d4b02df3f8cbc51b35b31208c4127b45d60f431 Mon Sep 17 00:00:00 2001
From: Nikita Uvarov <uv.nikita@gmail.com>
Date: Mon, 29 Oct 2018 12:26:18 +0100
Subject: [PATCH] nixos/containers: don't create veths if not configured

Previously, setting "privateNetwork = true" without specifying host and
local addresses would create unconfigured interfaces: ve-$INSTANCE on the host
and eth0 inside the container.

These changes is rebased part of the original PR #3021.
---
 nixos/modules/virtualisation/containers.nix | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/nixos/modules/virtualisation/containers.nix b/nixos/modules/virtualisation/containers.nix
index 8fe59badd335..50ee89168eee 100644
--- a/nixos/modules/virtualisation/containers.nix
+++ b/nixos/modules/virtualisation/containers.nix
@@ -36,7 +36,7 @@ let
         #! ${pkgs.runtimeShell} -e
 
         # Initialise the container side of the veth pair.
-        if [ "$PRIVATE_NETWORK" = 1 ]; then
+        if [ -n "$HOST_ADDRESS" ] || [ -n "$LOCAL_ADDRESS" ]; then
 
           ip link set host0 name eth0
           ip link set dev eth0 up
@@ -85,6 +85,10 @@ let
       cp --remove-destination /etc/resolv.conf "$root/etc/resolv.conf"
 
       if [ "$PRIVATE_NETWORK" = 1 ]; then
+        extraFlags+=" --private-network"
+      fi
+
+      if [ -n "$HOST_ADDRESS" ] || [ -n "$LOCAL_ADDRESS" ]; then
         extraFlags+=" --network-veth"
         if [ -n "$HOST_BRIDGE" ]; then
           extraFlags+=" --network-bridge=$HOST_BRIDGE"
@@ -153,7 +157,7 @@ let
       # Clean up existing machined registration and interfaces.
       machinectl terminate "$INSTANCE" 2> /dev/null || true
 
-      if [ "$PRIVATE_NETWORK" = 1 ]; then
+      if [ -n "$HOST_ADDRESS" ] || [ -n "$LOCAL_ADDRESS" ]; then
         ip link del dev "ve-$INSTANCE" 2> /dev/null || true
         ip link del dev "vb-$INSTANCE" 2> /dev/null || true
       fi
@@ -200,7 +204,7 @@ let
           '';
     in
       ''
-        if [ "$PRIVATE_NETWORK" = 1 ]; then
+        if [ -n "$HOST_ADDRESS" ] || [ -n "$LOCAL_ADDRESS" ]; then
           if [ -z "$HOST_BRIDGE" ]; then
             ifaceHost=ve-$INSTANCE
             ip link set dev $ifaceHost up
@@ -349,7 +353,7 @@ let
         List of forwarded ports from host to container. Each forwarded port
         is specified by protocol, hostPort and containerPort. By default,
         protocol is tcp and hostPort and containerPort are assumed to be
-        the same if containerPort is not explicitly given. 
+        the same if containerPort is not explicitly given.
       '';
     };
 
@@ -694,7 +698,7 @@ in
     # container so that container@.target can get the container
     # configuration.
     environment.etc =
-      let mkPortStr = p: p.protocol + ":" + (toString p.hostPort) + ":" + (if p.containerPort == null then toString p.hostPort else toString p.containerPort); 
+      let mkPortStr = p: p.protocol + ":" + (toString p.hostPort) + ":" + (if p.containerPort == null then toString p.hostPort else toString p.containerPort);
       in mapAttrs' (name: cfg: nameValuePair "containers/${name}.conf"
       { text =
           ''