diff options
| -rw-r--r-- | content.tex | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/content.tex b/content.tex index 546bef7..222b78e 100644 --- a/content.tex +++ b/content.tex @@ -3073,6 +3073,11 @@ features. \item[VIRTIO_NET_F_CTRL_GUEST_OFFLOADS (2)] Control channel offloads reconfiguration support. +\item[VIRTIO_NET_F_MTU(3)] Device maximum MTU reporting is supported. If + offered by the device, device advises driver about the value of + its maximum MTU. If negotiated, the driver uses \field{mtu} as + the maximum MTU value. + \item[VIRTIO_NET_F_MAC (5)] Device has given MAC address. \item[VIRTIO_NET_F_GUEST_TSO4 (7)] Driver can receive TSOv4. @@ -3164,11 +3169,16 @@ of each of transmit and receive virtqueues (receiveq1\ldots receiveqN and transmitq1\ldots transmitqN respectively) that can be configured once VIRTIO_NET_F_MQ is negotiated. +The following driver-read-only field, \field{mtu} only exists if +VIRTIO_NET_F_MTU is set. This field specifies the maximum MTU for the driver to +use. + \begin{lstlisting} struct virtio_net_config { u8 mac[6]; le16 status; le16 max_virtqueue_pairs; + le16 mtu; }; \end{lstlisting} @@ -3177,6 +3187,23 @@ struct virtio_net_config { The device MUST set \field{max_virtqueue_pairs} to between 1 and 0x8000 inclusive, if it offers VIRTIO_NET_F_MQ. +The device MUST set \field{mtu} to between 68 and 65535 inclusive, +if it offers VIRTIO_NET_F_MTU. + +The device SHOULD set \field{mtu} to at least 1280, if it offers +VIRTIO_NET_F_MTU. + +The device MUST NOT modify \field{mtu} once it has been set. + +The device MUST NOT pass received packets that exceed \field{mtu} (plus low +level ethernet header length) size with \field{gso_type} NONE or ECN +after VIRTIO_NET_F_MTU has been successfully negotiated. + +The device MUST forward transmitted packets of up to \field{mtu} (plus low +level ethernet header length) size with \field{gso_type} NONE or ECN, and do +so without fragmentation, after VIRTIO_NET_F_MTU has been successfully +negotiated. + \drivernormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout} A driver SHOULD negotiate VIRTIO_NET_F_MAC if the device offers it. @@ -3189,6 +3216,16 @@ If the driver does not negotiate the VIRTIO_NET_F_STATUS feature, it SHOULD assume the link is active, otherwise it SHOULD read the link status from the bottom bit of \field{status}. +A driver SHOULD negotiate VIRTIO_NET_F_MTU if the device offers it. + +If the driver negotiates VIRTIO_NET_F_MTU, it MUST supply enough receive +buffers to receive at least one receive packet of size \field{mtu} (plus low +level ethernet header length) with \field{gso_type} NONE or ECN. + +If the driver negotiates VIRTIO_NET_F_MTU, it MUST NOT transmit packets of +size exceeding the value of \field{mtu} (plus low level ethernet header length) +with \field{gso_type} NONE or ECN. + \subsubsection{Legacy Interface: Device configuration layout}\label{sec:Device Types / Network Device / Device configuration layout / Legacy Interface: Device configuration layout} \label{sec:Device Types / Block Device / Feature bits / Device configuration layout / Legacy Interface: Device configuration layout} When using the legacy interface, transitional devices and drivers |