[PATCH qemu-server v2 2/2] virtio-net: expose host_tunnel option

[Fiona Ebner <f.ebner@proxmox.com>]

Since the option is disabled starting with machine version 11.0+pve1
as a workaround to bug #7627, give users the possibility to explicitly
enable the option again.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 src/PVE/QemuServer.pm         | 11 +++++++++--
 src/PVE/QemuServer/Network.pm | 10 ++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index ec0423af..cdf66e89 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -1422,8 +1422,15 @@ sub print_netdevice_full {
     # FIXME: MAJOR VERSION: consider re-enabling by default if most guest kernels are expected to
     # include the fix "virtio_net: do not allow tunnel csum offload for non GSO packets" with a
     # prominent notice in the upgrade guide.
-    if (min_version($machine_version, 11, 0, 1) && $net->{model} eq 'virtio') {
-        $tmpstr .= ",host_tunnel=off";
+    if ($net->{model} eq 'virtio') {
+        if (min_version($machine_version, 11, 0, 1)) {
+            # Turn off if not explicitly enabled starting with 11.0+pve1
+            $tmpstr .= ",host_tunnel=off" if !$net->{'host-tunnel'};
+        } elsif (min_version($machine_version, 10, 2)) {
+            # The feature was introduced in QEMU 10.2. Turn off if explicitly disabled.
+            $tmpstr .= ",host_tunnel=off"
+                if defined($net->{'host-tunnel'}) && !$net->{'host-tunnel'};
+        }
     }
 
     return $tmpstr;
diff --git a/src/PVE/QemuServer/Network.pm b/src/PVE/QemuServer/Network.pm
index eb8222e8..11bebdec 100644
--- a/src/PVE/QemuServer/Network.pm
+++ b/src/PVE/QemuServer/Network.pm
@@ -116,6 +116,16 @@ my $net_fmt = {
             "Force MTU of network device (VirtIO only). Setting to '1' or empty will use the bridge MTU",
         optional => 1,
     },
+    'host-tunnel' => {
+        type => 'boolean',
+        description => 'Enable host GSO over UDP tunnel offload. (VirtIO only).',
+        verbose_description =>
+            'Enable host GSO over UDP tunnel offload (VirtIO only). Requires QEMU > 10.2 and guest'
+            . ' and host kernel support. Disabled by default starting with machine version'
+            . ' 11.0+pve1 to work around an issue with the virtio-net driver in guest kernels. With'
+            . ' machine versions 10.2 and 11.0, this is enabled by default.',
+        optional => 1,
+    },
 };
 
 our $netdesc = {
-- 
2.47.3