diff mbox series

[3/4] public/io/netif: specify MTU override node

Message ID 20200730194858.28523-4-paul@xen.org
State Superseded
Headers show
Series tools: propagate bridge MTU to vif frontends | expand

Commit Message

Paul Durrant July 30, 2020, 7:48 p.m. UTC
From: Paul Durrant <pdurrant@amazon.com>

There is currently no documentation to state what MTU a frontend should
adertise to its network stack. It has however long been assumed that the
default value of 1500 is correct.

This patch specifies a mechanism to allow the tools to set the MTU via a
xenstore node in the frontend area and states that the absence of that node
means the frontend should assume an MTU of 1500 octets.

NOTE: The Windows PV frontend has used an MTU sampled from the xenstore
      node specified in this patch.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Juergen Gross <jgross@suse.com>
---
 xen/include/public/io/netif.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

Juergen Gross Aug. 3, 2020, 5:08 a.m. UTC | #1
On 30.07.20 21:48, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@amazon.com>
> 
> There is currently no documentation to state what MTU a frontend should
> adertise to its network stack. It has however long been assumed that the
> default value of 1500 is correct.
> 
> This patch specifies a mechanism to allow the tools to set the MTU via a
> xenstore node in the frontend area and states that the absence of that node
> means the frontend should assume an MTU of 1500 octets.
> 
> NOTE: The Windows PV frontend has used an MTU sampled from the xenstore
>        node specified in this patch.
> 
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>

Can you please update docs/misc/xenstore-paths.pandoc accordingly?
With that you can have my:

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen
Durrant, Paul Aug. 3, 2020, 8:14 a.m. UTC | #2
> -----Original Message-----
> From: Jürgen Groß <jgross@suse.com>
> Sent: 03 August 2020 06:09
> To: Paul Durrant <paul@xen.org>; xen-devel@lists.xenproject.org
> Cc: Durrant, Paul <pdurrant@amazon.co.uk>
> Subject: RE: [EXTERNAL] [PATCH 3/4] public/io/netif: specify MTU override node
> 
> On 30.07.20 21:48, Paul Durrant wrote:
> > From: Paul Durrant <pdurrant@amazon.com>
> >
> > There is currently no documentation to state what MTU a frontend should
> > adertise to its network stack. It has however long been assumed that the
> > default value of 1500 is correct.
> >
> > This patch specifies a mechanism to allow the tools to set the MTU via a
> > xenstore node in the frontend area and states that the absence of that node
> > means the frontend should assume an MTU of 1500 octets.
> >
> > NOTE: The Windows PV frontend has used an MTU sampled from the xenstore
> >        node specified in this patch.
> >
> > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> 
> Can you please update docs/misc/xenstore-paths.pandoc accordingly?

Sure. Given the path is for use by tools then it should indeed be documented there as well.

> With that you can have my:
> 
> Reviewed-by: Juergen Gross <jgross@suse.com>
> 

Thanks,

  Paul

> 
> Juergen
diff mbox series

Patch

diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
index 9fcf91a2fe..00dd258712 100644
--- a/xen/include/public/io/netif.h
+++ b/xen/include/public/io/netif.h
@@ -204,6 +204,18 @@ 
  * present).
  */
 
+/*
+ * MTU
+ * ===
+ *
+ * The toolstack may set a value of MTU for the frontend by setting the
+ * /local/domain/<domid>/device/vif/<vif>/mtu node with the MTU value in
+ * octets. If this node is absent the frontend should assume an MTU value
+ * of 1500 octets. A frontend is also at liberty to ignore this value so
+ * it is only suitable for informing the frontend that a packet payload
+ * >1500 octets is permitted.
+ */
+
 /*
  * Hash types
  * ==========