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From: Paul Durrant <paul@xen.org>
To: xen-devel@lists.xenproject.org
Cc: Juergen Gross <jgross@suse.com>, Paul Durrant <pdurrant@amazon.com>
Subject: [PATCH 3/4] public/io/netif: specify MTU override node
Date: Thu, 30 Jul 2020 20:48:57 +0100	[thread overview]
Message-ID: <20200730194858.28523-4-paul@xen.org> (raw)
In-Reply-To: <20200730194858.28523-1-paul@xen.org>

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(+)

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
  * ==========
-- 
2.20.1



  parent reply	other threads:[~2020-07-30 19:49 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 19:48 [PATCH 0/4] tools: propagate bridge MTU to vif frontends Paul Durrant
2020-07-30 19:48 ` [PATCH 1/4] tools/hotplug: add remove_from_bridge() and improve debug output Paul Durrant
2020-07-30 19:48 ` [PATCH 2/4] tools/hotplug: combine add/online and remove/offline in vif-bridge Paul Durrant
2020-07-30 19:48 ` Paul Durrant [this message]
2020-08-03  5:08   ` [PATCH 3/4] public/io/netif: specify MTU override node Jürgen Groß
2020-08-03  8:14     ` Durrant, Paul
2020-07-30 19:48 ` [PATCH 4/4] tools/hotplug: modify set_mtu() to inform the frontend via xenstore Paul Durrant

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