[PATCH] NetTestSlave: wait for result when creating a netns

[Ondrej Lichtner]

From: Ondrej Lichtner <olichtne(a)redhat.com&gt;

When the lnst-slave process forks, the parent process should wait for
the result returned by rest of the add_namespace method. Otherwise 2
result messages are created, which could cause the Ctl <-> Slave message
lock-step to be desynchronized and cause race condition issues.

Signed-off-by: Ondrej Lichtner <olichtne(a)redhat.com&gt;
---
 lnst/Slave/NetTestSlave.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lnst/Slave/NetTestSlave.py b/lnst/Slave/NetTestSlave.py
index 8e26b4b..f11ca8b 100644
--- a/lnst/Slave/NetTestSlave.py
+++ b/lnst/Slave/NetTestSlave.py
@@ -670,7 +670,8 @@ class SlaveMethods:
                 self._net_namespaces[netns] = {"pid": pid,
                                                "pipe": read_pipe}
                 self._server_handler.add_netns(netns, read_pipe)
-                return False
+                result = self._slave_server.wait_for_result(netns)
+                return result["result"]
             elif pid == 0:
                 self._slave_server.set_netns_sighandlers()
                 #create new network namespace
-- 
2.11.0

[Jan Tluka]

Fri, Jan 20, 2017 at 03:16:19PM CET, olichtne(a)redhat.com wrote:
> From: Ondrej Lichtner <olichtne(a)redhat.com&gt;
>
> When the lnst-slave process forks, the parent process should wait for
> the result returned by rest of the add_namespace method. Otherwise 2
> result messages are created, which could cause the Ctl <-> Slave message
> lock-step to be desynchronized and cause race condition issues.
>
> Signed-off-by: Ondrej Lichtner <olichtne(a)redhat.com&gt;
> ---
>  lnst/Slave/NetTestSlave.py | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lnst/Slave/NetTestSlave.py b/lnst/Slave/NetTestSlave.py
> index 8e26b4b..f11ca8b 100644
> --- a/lnst/Slave/NetTestSlave.py
> +++ b/lnst/Slave/NetTestSlave.py
> @@ -670,7 +670,8 @@ class SlaveMethods:
>                  self._net_namespaces[netns] = {"pid": pid,
>                                                 "pipe": read_pipe}
>                  self._server_handler.add_netns(netns, read_pipe)
> -                return False
> +                result = self._slave_server.wait_for_result(netns)
> +                return result["result"]
>              elif pid == 0:
>                  self._slave_server.set_netns_sighandlers()
>                  #create new network namespace
> -- 
> 2.11.0
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I tested this patch and it fixes the issue I'm having.

Acked-by: Jan Tluka <jtluka(a)redhat.com&gt;

[Jan Tluka]

Fri, Jan 20, 2017 at 03:16:19PM CET, olichtne(a)redhat.com wrote:
> From: Ondrej Lichtner <olichtne(a)redhat.com&gt;
>
> When the lnst-slave process forks, the parent process should wait for
> the result returned by rest of the add_namespace method. Otherwise 2
> result messages are created, which could cause the Ctl <-> Slave message
> lock-step to be desynchronized and cause race condition issues.
>
> Signed-off-by: Ondrej Lichtner <olichtne(a)redhat.com&gt; 
Pushed, thanks!

-Jan