From 7511655807e90aa33ea7b71991401a79ec36bb41 Mon Sep 17 00:00:00 2001
From: Philip Sequeira <phsequei@gmail.com>
Date: Thu, 5 Apr 2018 14:04:27 +0000
Subject: [PATCH] nspawn: wait for network namespace creation before interface
 setup (#8633)

Otherwise, network interfaces can be "moved" into the container's
namespace while it's still the same as the host namespace, in which case
e.g. host0 for a veth ends up on the host side instead of inside the
container.

Regression introduced in 0441378080489e4ab6704cd0a2d78cb1ceaca899.

Fixes #8599.
---
 src/nspawn/nspawn.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 810f1247ea2..a5bc50c1f4c 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -2329,6 +2329,9 @@ static int inner_child(
                 r = unshare(CLONE_NEWNET);
                 if (r < 0)
                         return log_error_errno(errno, "Failed to unshare network namespace: %m");
+
+                /* Tell the parent that it can setup network interfaces. */
+                (void) barrier_place(barrier); /* #3 */
         }
 
         r = mount_sysfs(NULL, arg_mount_settings);
@@ -2337,7 +2340,7 @@ static int inner_child(
 
         /* Wait until we are cgroup-ified, so that we
          * can mount the right cgroup path writable */
-        if (!barrier_place_and_sync(barrier)) { /* #3 */
+        if (!barrier_place_and_sync(barrier)) { /* #4 */
                 log_error("Parent died too early");
                 return -ESRCH;
         }
@@ -2448,7 +2451,7 @@ static int inner_child(
         /* Let the parent know that we are ready and
          * wait until the parent is ready with the
          * setup, too... */
-        if (!barrier_place_and_sync(barrier)) { /* #4 */
+        if (!barrier_place_and_sync(barrier)) { /* #5 */
                 log_error("Parent died too early");
                 return -ESRCH;
         }
@@ -3533,6 +3536,14 @@ static int run(int master,
 
         if (arg_private_network) {
 
+                if (!arg_network_namespace_path) {
+                        /* Wait until the child has unshared its network namespace. */
+                        if (!barrier_place_and_sync(&barrier)) { /* #3 */
+                                log_error("Child died too early");
+                                return -ESRCH;
+                        }
+                }
+
                 r = move_network_interfaces(*pid, arg_network_interfaces);
                 if (r < 0)
                         return r;
@@ -3656,7 +3667,7 @@ static int run(int master,
          * its setup (including cgroup-ification), and that
          * the child can now hand over control to the code to
          * run inside the container. */
-        (void) barrier_place(&barrier); /* #3 */
+        (void) barrier_place(&barrier); /* #4 */
 
         /* Block SIGCHLD here, before notifying child.
          * process_pty() will handle it with the other signals. */
@@ -3684,7 +3695,7 @@ static int run(int master,
                 return r;
 
         /* Let the child know that we are ready and wait that the child is completely ready now. */
-        if (!barrier_place_and_sync(&barrier)) { /* #4 */
+        if (!barrier_place_and_sync(&barrier)) { /* #5 */
                 log_error("Child died too early.");
                 return -ESRCH;
         }