From fbc7011346c7c286fb893a72a79068ffc9f9ce5e Mon Sep 17 00:00:00 2001
From: Rob Bradford <robert.bradford@intel.com>
Date: Wed, 28 Apr 2021 14:33:54 +0100
Subject: [PATCH] virtio-devices: net: Tolerate unsupported control queue
 commands

Rather than erroring out and stalling the queue instead report an error
message if the command is invalid and return an error to the guest via
the status field.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
---
 virtio-devices/src/net_util.rs | 47 +++++++++++++++++-----------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/virtio-devices/src/net_util.rs b/virtio-devices/src/net_util.rs
index b60a872d6..90f53192a 100644
--- a/virtio-devices/src/net_util.rs
+++ b/virtio-devices/src/net_util.rs
@@ -39,10 +39,6 @@ unsafe impl ByteValued for VirtioNetConfig {}
 pub enum Error {
     /// Read queue failed.
     GuestMemory(GuestMemoryError),
-    /// Invalid ctrl class
-    InvalidCtlClass,
-    /// Invalid ctrl command
-    InvalidCtlCmd,
     /// No queue pairs number.
     NoQueuePairsDescriptor,
     /// No status descriptor
@@ -75,17 +71,19 @@ impl NetCtrl {
         for avail_desc in queue.iter(&mem) {
             let ctrl_hdr: ControlHeader =
                 mem.read_obj(avail_desc.addr).map_err(Error::GuestMemory)?;
-            match u32::from(ctrl_hdr.class) {
-                VIRTIO_NET_CTRL_MQ => {
-                    let mq_desc = avail_desc
-                        .next_descriptor()
-                        .ok_or(Error::NoQueuePairsDescriptor)?;
-                    let queue_pairs = mem
-                        .read_obj::<u16>(mq_desc.addr)
-                        .map_err(Error::GuestMemory)?;
-                    let status_desc = mq_desc.next_descriptor().ok_or(Error::NoStatusDescriptor)?;
+            let data_desc = avail_desc
+                .next_descriptor()
+                .ok_or(Error::NoQueuePairsDescriptor)?;
+            let status_desc = data_desc
+                .next_descriptor()
+                .ok_or(Error::NoStatusDescriptor)?;
 
-                    let ok = if u32::from(ctrl_hdr.cmd) != VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET {
+            let ok = match u32::from(ctrl_hdr.class) {
+                VIRTIO_NET_CTRL_MQ => {
+                    let queue_pairs = mem
+                        .read_obj::<u16>(data_desc.addr)
+                        .map_err(Error::GuestMemory)?;
+                    if u32::from(ctrl_hdr.cmd) != VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET {
                         warn!("Unsupported command: {}", ctrl_hdr.cmd);
                         false
                     } else if (queue_pairs < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN as u16)
@@ -96,16 +94,19 @@ impl NetCtrl {
                     } else {
                         info!("Number of MQ pairs requested: {}", queue_pairs);
                         true
-                    };
-
-                    mem.write_obj(
-                        if ok { VIRTIO_NET_OK } else { VIRTIO_NET_ERR } as u8,
-                        status_desc.addr,
-                    )
-                    .map_err(Error::GuestMemory)?;
+                    }
                 }
-                _ => return Err(Error::InvalidCtlClass),
-            }
+                _ => {
+                    warn!("Unsupported command {:?}", ctrl_hdr);
+                    false
+                }
+            };
+
+            mem.write_obj(
+                if ok { VIRTIO_NET_OK } else { VIRTIO_NET_ERR } as u8,
+                status_desc.addr,
+            )
+            .map_err(Error::GuestMemory)?;
             used_desc_heads[used_count] = (avail_desc.index, avail_desc.len);
             used_count += 1;
         }