Re: [virtio-dev] [PATCH v17] virtio-net: support inner header hash

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jun 20, 2023 at 06:52:22PM +0800, Heng Qi wrote:
> 
> 
> å 2023/6/15 äå5:29, Heng Qi åé:
> > 
> > Hi all!
> > 
> > If after reviewing it you feel this version meets the
> > necessaryrequirements,
> > I kindly request a vote.
> > 
> > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/173
> 
> I would like to make a humble request that if there are no questions to this
> version,
> I sincerely ask the chairs to open the voting channel!
> 
> Thanks!

Sorry this was posted while I was traveling for kvm forum.
Will review now.

> > 
> > 
> > 
> > å 2023/6/12 äå4:09, Heng Qi åé:
> > > 1. Currently, a received encapsulated packet has an outer and an
> > > inner header, but
> > > the virtio device is unable to calculate the hash for the inner
> > > header. The same
> > > flow can traverse through different tunnels, resulting in the
> > > encapsulated
> > > packets being spread across multiple receive queues (refer to the
> > > figure below).
> > > However, in certain scenarios, we may need to direct these
> > > encapsulated packets of
> > > the same flow to a single receive queue. This facilitates the processing
> > > of the flow by the same CPU to improve performance (warm caches,
> > > less locking, etc.).
> > > 
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ client1ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ client2
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |ÂÂÂÂÂÂÂ +-------+ÂÂÂÂÂÂÂÂ |
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +------->|tunnels|<--------+
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +-------+
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â |
> > >  v v
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +-----------------+
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ | monitoring host |
> > > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ +-----------------+
> > > 
> > > To achieve this, the device can calculate a symmetric hash based on
> > > the inner headers
> > > of the same flow.
> > > 
> > > 2. For legacy systems, they may lack entropy fields which modern
> > > protocols have in
> > > the outer header, resulting in multiple flows with the same outer
> > > header but
> > > different inner headers being directed to the same receive queue.
> > > This results in
> > > poor receive performance.
> > > 
> > > To address this limitation, inner header hash can be used to enable
> > > the device to advertise
> > > the capability to calculate the hash for the inner packet, regaining
> > > better receive performance.
> > > 
> > > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/173
> > > 
> > > Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> > > Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > Reviewed-by: Parav Pandit <parav@nvidia.com>
> > > ---
> > > v16->v17:
> > > ÂÂÂÂ1. Some small rewrites. @Parav Pandit
> > > ÂÂÂÂ2. Add Parav's Reviewed-by tag (Thanks!).
> > > 
> > > v15->v16:
> > > ÂÂÂÂ1. Remove the hash_option. In order to delimit the inner header
> > > hash and RSS
> > > ÂÂÂÂÂÂ configuration, the ability to configure the outer src udp
> > > port hash is given
> > > ÂÂÂÂÂÂ to RSS. This is orthogonal to inner header hash, which will
> > > be done in the
> > > ÂÂÂÂÂÂ RSS capability extension topic (considered as an RSS
> > > extension together
> > > ÂÂÂÂÂÂ with the symmetric toeplitz hash algorithm, etc.). @Parav
> > > Pandit @Michael S . Tsirkin
> > > ÂÂÂÂ2. Fix a 'field' typo. @Parav Pandit
> > > 
> > > v14->v15:
> > > ÂÂÂÂ1. Add tunnel hash option suggested by @Michael S . Tsirkin
> > > ÂÂÂÂ2. Adjust some descriptions.
> > > 
> > > v13->v14:
> > > ÂÂÂÂ1. Move supported_hash_tunnel_types from config space into cvq
> > > command. @Parav Pandit
> > > ÂÂÂÂ2. Rebase to master branch.
> > > ÂÂÂÂ3. Some minor modifications.
> > > 
> > > v12->v13:
> > > ÂÂÂÂ1. Add a GET command for hash_tunnel_types. @Parav Pandit
> > > ÂÂÂÂ2. Add tunneling protocol explanation. @Jason Wang
> > > ÂÂÂÂ3. Add comments on some usage scenarios for inner hash.
> > > 
> > > v11->v12:
> > > ÂÂÂÂ1. Add a command VIRTIO_NET_CTRL_MQ_TUNNEL_CONFIG.
> > > ÂÂÂÂ2. Refine the commit log. @Michael S . Tsirkin
> > > ÂÂÂÂ3. Add some tunnel types.
> > > 
> > > v10->v11:
> > > ÂÂÂÂ1. Revise commit log for clarity for readers.
> > > ÂÂÂÂ2. Some modifications to avoid undefined terms. @Parav Pandit
> > > ÂÂÂÂ3. Change VIRTIO_NET_F_HASH_TUNNEL dependency. @Parav Pandit
> > > ÂÂÂÂ4. Add the normative statements. @Parav Pandit
> > > 
> > > v9->v10:
> > > ÂÂÂÂ1. Removed hash_report_tunnel related information. @Parav Pandit
> > > ÂÂÂÂ2. Re-describe the limitations of QoS for tunneling.
> > > ÂÂÂÂ3. Some clarification.
> > > 
> > > v8->v9:
> > > ÂÂÂÂ1. Merge hash_report_tunnel_types into hash_report. @Parav Pandit
> > > ÂÂÂÂ2. Add tunnel security section. @Michael S . Tsirkin
> > > ÂÂÂÂ3. Add VIRTIO_NET_F_HASH_REPORT_TUNNEL.
> > > ÂÂÂÂ4. Fix some typos.
> > > ÂÂÂÂ5. Add more tunnel types. @Michael S . Tsirkin
> > > 
> > > v7->v8:
> > > ÂÂÂÂ1. Add supported_hash_tunnel_types. @Jason Wang, @Parav Pandit
> > > ÂÂÂÂ2. Change hash_report_tunnel to hash_report_tunnel_types. @Parav
> > > Pandit
> > > ÂÂÂÂ3. Removed re-definition for inner packet hashing. @Parav Pandit
> > > ÂÂÂÂ4. Fix some typos. @Michael S . Tsirkin
> > > ÂÂÂÂ5. Clarify some sentences. @Michael S . Tsirkin
> > > 
> > > v6->v7:
> > > ÂÂÂÂ1. Modify the wording of some sentences for clarity. @Michael S.
> > > Tsirkin
> > > ÂÂÂÂ2. Fix some syntax issues. @Michael S. Tsirkin
> > > 
> > > v5->v6:
> > > ÂÂÂÂ1. Fix some syntax and capitalization issues. @Michael S. Tsirkin
> > > ÂÂÂÂ2. Use encapsulated/encaptulation uniformly. @Michael S. Tsirkin
> > > ÂÂÂÂ3. Move the links to introduction section. @Michael S. Tsirkin
> > > ÂÂÂÂ4. Clarify some sentences. @Michael S. Tsirkin
> > > 
> > > v4->v5:
> > > ÂÂÂÂ1. Clarify some paragraphs. @Cornelia Huck
> > > ÂÂÂÂ2. Fix the u8 type. @Cornelia Huck
> > > 
> > > v3->v4:
> > > ÂÂÂÂ1. Rename VIRTIO_NET_F_HASH_GRE_VXLAN_GENEVE_INNER to
> > > VIRTIO_NET_F_HASH_TUNNEL. @Jason Wang
> > > ÂÂÂÂ2. Make things clearer. @Jason Wang @Michael S. Tsirkin
> > > ÂÂÂÂ3. Keep the possibility to use inner hash for automatic receive
> > > steering. @Jason Wang
> > > ÂÂÂÂ4. Add the "Tunnel packet" paragraph to avoid repeating the GRE
> > > etc. many times. @Michael S. Tsirkin
> > > 
> > > v2->v3:
> > > ÂÂÂÂ1. Add a feature bit for GRE/VXLAN/GENEVE inner hash. @Jason Wang
> > > ÂÂÂÂ2. Chang \field{hash_tunnel} to \field{hash_report_tunnel}.
> > > @Jason Wang, @Michael S. Tsirkin
> > > 
> > > v1->v2:
> > > ÂÂÂÂ1. Remove the patch for the bitmask fix. @Michael S. Tsirkin
> > > ÂÂÂÂ2. Clarify some paragraphs. @Jason Wang
> > > ÂÂÂÂ3. Add \field{hash_tunnel} and VIRTIO_NET_HASH_REPORT_GRE. @Yuri
> > > Benditovich
> > > 
> > > Â device-types/net/description.texÂÂÂÂÂÂÂ | 161 ++++++++++++++++++++++++
> > > Â device-types/net/device-conformance.tex |ÂÂ 1 +
> > > Â device-types/net/driver-conformance.tex |ÂÂ 1 +
> > > Â introduction.texÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 40 ++++++
> > > Â 4 files changed, 203 insertions(+)
> > > 
> > > diff --git a/device-types/net/description.tex
> > > b/device-types/net/description.tex
> > > index 3030222..6bf65ff 100644
> > > --- a/device-types/net/description.tex
> > > +++ b/device-types/net/description.tex
> > > @@ -88,6 +88,8 @@ \subsection{Feature bits}\label{sec:Device Types /
> > > Network Device / Feature bits
> > > Â \item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control
> > > ÂÂÂÂÂ channel.
> > > Â +\item[VIRTIO_NET_F_HASH_TUNNEL(51)] Device supports inner header
> > > hash for tunnel-encapsulated packets.
> > > +
> > > Â \item[VIRTIO_NET_F_VQ_NOTF_COAL(52)] Device supports virtqueue
> > > notification coalescing.
> > > Â Â \item[VIRTIO_NET_F_NOTF_COAL(53)] Device supports notifications
> > > coalescing.
> > > @@ -147,6 +149,7 @@ \subsubsection{Feature bit
> > > requirements}\label{sec:Device Types / Network Device
> > > Â \item[VIRTIO_NET_F_RSC_EXT] Requires VIRTIO_NET_F_HOST_TSO4 or
> > > VIRTIO_NET_F_HOST_TSO6.
> > > Â \item[VIRTIO_NET_F_RSS] Requires VIRTIO_NET_F_CTRL_VQ.
> > > Â \item[VIRTIO_NET_F_VQ_NOTF_COAL] Requires VIRTIO_NET_F_CTRL_VQ.
> > > +\item[VIRTIO_NET_F_HASH_TUNNEL] Requires VIRTIO_NET_F_CTRL_VQ along
> > > with VIRTIO_NET_F_RSS and/or VIRTIO_NET_F_HASH_REPORT.
> > > Â \end{description}
> > > Â Â \subsubsection{Legacy Interface: Feature bits}\label{sec:Device
> > > Types / Network Device / Feature bits / Legacy Interface: Feature
> > > bits}
> > > @@ -869,6 +872,7 @@ \subsubsection{Processing of Incoming
> > > Packets}\label{sec:Device Types / Network
> > > Â If the feature VIRTIO_NET_F_RSS was negotiated:
> > > Â \begin{itemize}
> > > Â \item The device uses \field{hash_types} of the
> > > virtio_net_rss_config structure as 'Enabled hash types' bitmask.
> > > +\item The device uses \field{hash_tunnel_types} of the
> > > virtnet_hash_tunnel_config_get structure as 'Enabled encapsulation
> > > hash types' bitmask if VIRTIO_NET_F_HASH_TUNNEL was negotiated.
> > > Â \item The device uses a key as defined in \field{hash_key_data}
> > > and \field{hash_key_length} of the virtio_net_rss_config structure
> > > (see
> > > Â \ref{sec:Device Types / Network Device / Device Operation /
> > > Control Virtqueue / Receive-side scaling (RSS) / Setting RSS
> > > parameters}).
> > > Â \end{itemize}
> > > @@ -876,6 +880,7 @@ \subsubsection{Processing of Incoming
> > > Packets}\label{sec:Device Types / Network
> > > Â If the feature VIRTIO_NET_F_RSS was not negotiated:
> > > Â \begin{itemize}
> > > Â \item The device uses \field{hash_types} of the
> > > virtio_net_hash_config structure as 'Enabled hash types' bitmask.
> > > +\item The device uses \field{hash_tunnel_types} of the
> > > virtnet_hash_tunnel_config_get structure as 'Enabled encapsulation
> > > hash types' bitmask if VIRTIO_NET_F_HASH_TUNNEL was negotiated.
> > > Â \item The device uses a key as defined in \field{hash_key_data}
> > > and \field{hash_key_length} of the virtio_net_hash_config structure
> > > (see
> > > Â \ref{sec:Device Types / Network Device / Device Operation /
> > > Control Virtqueue / Automatic receive steering in multiqueue mode /
> > > Hash calculation}).
> > > Â \end{itemize}
> > > @@ -891,6 +896,7 @@ \subsubsection{Processing of Incoming
> > > Packets}\label{sec:Device Types / Network
> > > Â Â \subparagraph{Supported/enabled hash types}
> > > Â \label{sec:Device Types / Network Device / Device Operation /
> > > Processing of Incoming Packets / Hash calculation for incoming
> > > packets / Supported/enabled hash types}
> > > +This paragraph relies on definitions from
> > > \hyperref[intro:IP]{[IP]}, \hyperref[intro:UDP]{[UDP]} and
> > > \hyperref[intro:TCP]{[TCP]}.
> > > Â Hash types applicable for IPv4 packets:
> > > Â \begin{lstlisting}
> > > Â #define VIRTIO_NET_HASH_TYPE_IPv4ÂÂÂÂÂÂÂÂÂÂÂÂÂ (1 << 0)
> > > @@ -1001,6 +1007,161 @@ \subsubsection{Processing of Incoming
> > > Packets}\label{sec:Device Types / Network
> > > Â (see \ref{sec:Device Types / Network Device / Device Operation /
> > > Processing of Incoming Packets / Hash calculation for incoming
> > > packets / IPv6 packets without extension header}).
> > > Â \end{itemize}
> > > Â +\paragraph{Inner Header Hash}
> > > +\label{sec:Device Types / Network Device / Device Operation /
> > > Processing of Incoming Packets / Inner Header Hash}
> > > +
> > > +If VIRTIO_NET_F_HASH_TUNNEL has been negotiated, the driver can
> > > send commands VIRTIO_NET_CTRL_HASH_TUNNEL_SET
> > > +and VIRTIO_NET_CTRL_HASH_TUNNEL_GET for the inner header hash
> > > configuration.
> > > +
> > > +struct virtnet_hash_tunnel_config_set {
> > > +ÂÂÂ le32 hash_tunnel_types;
> > > +};
> > > +
> > > +struct virtnet_hash_tunnel_config_get {
> > > +ÂÂÂ le32 supported_hash_tunnel_types;
> > > +ÂÂÂ le32 hash_tunnel_types;
> > > +};
> > > +
> > > +#define VIRTIO_NET_CTRL_HASH_TUNNEL 7
> > > + #define VIRTIO_NET_CTRL_HASH_TUNNEL_SET 0
> > > + #define VIRTIO_NET_CTRL_HASH_TUNNEL_GET 1
> > > +
> > > +Field \field{supported_hash_tunnel_types} provided by the device
> > > indicates that the device supports inner header hash for these
> > > encapsulation types.
> > > +\field{supported_hash_tunnel_types} contains the bitmask of
> > > supported tunnel hash types. See \ref{sec:Device Types / Network
> > > Device / Device Operation / Processing
> > > +of Incoming Packets / Hash calculation for incoming packets /
> > > Supported/enabled encapsulation hash types}.
> > > +
> > > +Field \field{hash_tunnel_types} contains the bitmask of configured
> > > tunnel hash types.
> > > +See \ref{sec:Device Types / Network Device / Device Operation /
> > > Processing of Incoming Packets / Hash calculation for incoming
> > > packets / Supported/enabled encapsulation hash types}.
> > > +
> > > +The class VIRTIO_NET_CTRL_HASH_TUNNEL has the following commands:
> > > +\begin{itemize}
> > > +\item VIRTIO_NET_CTRL_HASH_TUNNEL_SET: set
> > > \field{hash_tunnel_types} for the device using the
> > > virtnet_hash_tunnel_config_set structure, which is read-only for the
> > > device.
> > > +\item VIRTIO_NET_CTRL_HASH_TUNNEL_GET: get
> > > \field{hash_tunnel_types} and \field{supported_hash_tunnel_types}
> > > from the device using the virtnet_hash_tunnel_config_get
> > > +ÂÂÂÂÂ structure, which is write-only for the device.
> > > +\end{itemize}
> > > +
> > > +\subparagraph{Tunnel/Encapsulated packet}
> > > +\label{sec:Device Types / Network Device / Device Operation /
> > > Processing of Incoming Packets / Hash calculation for incoming
> > > packets / Tunnel/Encapsulated packet}
> > > +
> > > +A tunnel packet is encapsulated from the original packet based on
> > > the tunneling protocol (only a single level of
> > > +encapsulation is currently supported). The encapsulated packet
> > > contains an outer header and an inner header, and
> > > +the device calculates the hash over either the inner header or the
> > > outer header.
> > > +
> > > +If VIRTIO_NET_F_HASH_TUNNEL is negotiated and a received
> > > encapsulated packet's outer header matches one of the
> > > +configured \field{hash_tunnel_types}, the hash of the inner header
> > > is calculated.
> > > +
> > > +Supported encapsulated packet types:
> > > +\begin{itemize}
> > > +\item The outer header of the following encapsulation types does
> > > not contain the transport protocol:
> > > +\begin{itemize}
> > > +\item \hyperref[intro:ipip]{[IPIP]}: the outer header is over IPv4
> > > and the inner header is over IPv4.
> > > +\item \hyperref[intro:nvgre]{[NVGRE]}: the outer header is over
> > > IPv4/IPv6 and the inner header is over IPv4/IPv6.
> > > +\item \hyperref[intro:gre_rfc2784]{[GRE_rfc2784]}: the outer header
> > > is over IPv4 and the inner header is over IPv4.
> > > +\item \hyperref[intro:gre_rfc2890]{[GRE_rfc2890]}: the outer header
> > > is over IPv4 and the inner header is over IPv4.
> > > +\item \hyperref[intro:gre_rfc7676]{[GRE_rfc7676]}: the outer header
> > > is over IPv4/IPv6 and the inner header is over IPv4/IPv6.
> > > +\end{itemize}
> > > +\item The outer header of the following encapsulation types uses
> > > UDP as the transport protocol:
> > > +\begin{itemize}
> > > +\item \hyperref[intro:vxlan]{[VXLAN]}: the outer header is over
> > > IPv4/IPv6 and the inner header is over IPv4/IPv6.
> > > +\item \hyperref[intro:geneve]{[GENEVE]}: the outer header is over
> > > IPv4/IPv6 and the inner header is over IPv4/IPv6.
> > > +\item \hyperref[intro:vxlan_gpe]{[VXLAN-GPE]}: the outer header is
> > > over IPv4/IPv6 and the inner header is over IPv4/IPv6.
> > > +\item \hyperref[intro:gre_in_udp_rfc8086]{[GRE-in-UDP]}: the outer
> > > header is over IPv4/IPv6 and the inner header is over IPv4/IPv6.
> > > +\end{itemize}
> > > +\end{itemize}
> > > +
> > > +If VIRTIO_NET_HASH_TUNNEL_TYPE_NONE is set or the encapsulation
> > > type is not included in the configured \field{hash_tunnel_types},
> > > +the hash of the outer header is calculated for the received
> > > encapsulated packet.
> > > +
> > > +The hash is calculated for the received non-encapsulated packet as
> > > if VIRTIO_NET_F_HASH_TUNNEL was not negotiated.
> > > +
> > > +\subparagraph{Supported/enabled encapsulation hash types}
> > > +\label{sec:Device Types / Network Device / Device Operation /
> > > Processing of Incoming Packets / Hash calculation for incoming
> > > packets / Supported/enabled encapsulation hash types}
> > > +
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_NONEÂÂÂÂÂÂÂ (1 << 0)
> > > +\end{lstlisting}
> > > +
> > > +Supported encapsulation hash types:
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:gre_rfc2784]{[GRE_rfc2784]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_GRE_2784ÂÂÂ (1 << 1)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:gre_rfc2890]{[GRE_rfc2890]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_GRE_2890ÂÂÂ (1 << 2)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:gre_rfc7676]{[GRE_rfc7676]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_GRE_7676ÂÂÂ (1 << 3)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:gre_in_udp_rfc8086]{[GRE-in-UDP]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_GRE_UDPÂÂÂÂ (1 << 4)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:vxlan]{[VXLAN]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_VXLANÂÂÂÂÂÂ (1 << 5)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:vxlan_gpe]{[VXLAN-GPE]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_VXLAN_GPEÂÂ (1 << 6)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:geneve]{[GENEVE]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_GENEVEÂÂÂÂÂ (1 << 7)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:ipip]{[IPIP]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_IPIPÂÂÂÂÂÂÂ (1 << 8)
> > > +\end{lstlisting}
> > > +Hash type applicable for inner payload of the
> > > \hyperref[intro:nvgre]{[NVGRE]} packet:
> > > +\begin{lstlisting}
> > > +#define VIRTIO_NET_HASH_TUNNEL_TYPE_NVGREÂÂÂÂÂÂ (1 << 9)
> > > +\end{lstlisting}
> > > +
> > > +\subparagraph{Advice}
> > > +Usage scenarios of inner header hash (but not limited to):
> > > +\begin{itemize}
> > > +\item Legacy tunneling protocols that lack entropy in the outer
> > > header use inner header hash to hash flows
> > > +ÂÂÂÂÂ with the same outer header but different inner headers to
> > > different queues for better-receiving performance.
> > > +\item In scenarios where the same flow passing through different
> > > tunnels is expected to be received in the same queue,
> > > +ÂÂÂÂÂ to utilize warm caches, to have less locking etc. are
> > > optimized to obtain receiving performance.
> > > +\end{itemize}
> > > +
> > > +For scenarios with sufficient outer entropy or no inner header hash
> > > requirements, inner header hash may not be needed:
> > > +A tunnel is often expected to isolate the external network from the
> > > internal one. By completely ignoring entropy
> > > +in the outer header and replacing it with entropy from the inner
> > > header, for hash calculations, this expectation
> > > +might be violated to a certain extent, depending on how the hash is
> > > used. When the hash use is limited to RSS queue
> > > +selection, inner header hash may have quality of service (QoS)
> > > limitations.
> > > +
> > > +Possible mitigations:
> > > +\begin{itemize}
> > > +\item Use a tool with good forwarding performance to keep the
> > > receive queue from dropping packets.
> > > +\item If the QoS is unavailable, the driver can set
> > > \field{hash_tunnel_types} to VIRTIO_NET_HASH_TUNNEL_TYPE_NONE
> > > +ÂÂÂÂÂ to disable inner header hash for encapsulated packets.
> > > +\item Perform appropriate QoS before packets consume the receive
> > > buffers of the receive queues.
> > > +\end{itemize}
> > > +
> > > +\devicenormative{\subparagraph}{Inner Header Hash}{Device Types /
> > > Network Device / Device Operation / Control Virtqueue / Inner Header
> > > Hash}
> > > +
> > > +The device MUST calculate the hash on the outer header if the type
> > > of the received encapsulated packet does not match
> > > +any value of the configured \field{hash_tunnel_types}.
> > > +
> > > +The device MUST respond to the VIRTIO_NET_CTRL_HASH_TUNNEL_SET
> > > command with VIRTIO_NET_ERR if the device receives
> > > +an unsupported or unrecognized VIRTIO_NET_HASH_TUNNEL_TYPE_ flag.
> > > +
> > > +The device MUST provide the values of
> > > \field{supported_hash_tunnel_types} if it offers the
> > > VIRTIO_NET_F_HASH_TUNNEL feature.
> > > +
> > > +Upon reset, the device MUST initialize \field{hash_tunnel_type} to 0.
> > > +
> > > +\drivernormative{\subparagraph}{Inner Header Hash}{Device Types /
> > > Network Device / Device Operation / Control Virtqueue / Inner Header
> > > Hash}
> > > +
> > > +The driver MUST have negotiated the VIRTIO_NET_F_HASH_TUNNEL
> > > feature when issuing commands VIRTIO_NET_CTRL_HASH_TUNNEL_SET and
> > > VIRTIO_NET_CTRL_HASH_TUNNEL_GET.
> > > +
> > > +The driver MUST ignore the values received from the
> > > VIRTIO_NET_CTRL_HASH_TUNNEL_GET command if the device responds with
> > > VIRTIO_NET_ERR.
> > > +
> > > +The driver MUST NOT set any VIRTIO_NET_HASH_TUNNEL_TYPE_ flags
> > > which are not supported by the device.
> > > +
> > > Â \paragraph{Hash reporting for incoming packets}
> > > Â \label{sec:Device Types / Network Device / Device Operation /
> > > Processing of Incoming Packets / Hash reporting for incoming
> > > packets}
> > > Â diff --git a/device-types/net/device-conformance.tex
> > > b/device-types/net/device-conformance.tex
> > > index 54f6783..f88f48b 100644
> > > --- a/device-types/net/device-conformance.tex
> > > +++ b/device-types/net/device-conformance.tex
> > > @@ -14,4 +14,5 @@
> > > Â \item \ref{devicenormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Automatic receive steering in
> > > multiqueue mode}
> > > Â \item \ref{devicenormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS
> > > processing}
> > > Â \item \ref{devicenormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Notifications Coalescing}
> > > +\item \ref{devicenormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Inner Header Hash}
> > > Â \end{itemize}
> > > diff --git a/device-types/net/driver-conformance.tex
> > > b/device-types/net/driver-conformance.tex
> > > index 97d0cc1..9d853d9 100644
> > > --- a/device-types/net/driver-conformance.tex
> > > +++ b/device-types/net/driver-conformance.tex
> > > @@ -14,4 +14,5 @@
> > > Â \item \ref{drivernormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Offloads State Configuration /
> > > Setting Offloads State}
> > > Â \item \ref{drivernormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Receive-side scaling (RSS) }
> > > Â \item \ref{drivernormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Notifications Coalescing}
> > > +\item \ref{drivernormative:Device Types / Network Device / Device
> > > Operation / Control Virtqueue / Inner Header Hash}
> > > Â \end{itemize}
> > > diff --git a/introduction.tex b/introduction.tex
> > > index b7155bf..3f34950 100644
> > > --- a/introduction.tex
> > > +++ b/introduction.tex
> > > @@ -102,6 +102,46 @@ \section{Normative
> > > References}\label{sec:Normative References}
> > > ÂÂÂÂÂ Standards for Efficient Cryptography Group(SECG), ``SEC1:
> > > Elliptic Cureve Cryptography'', Version 1.0, September 2000.
> > > ÂÂÂÂÂ \newline\url{https://www.secg.org/sec1-v2.pdf}\\
> > > Â + \phantomsection\label{intro:gre_rfc2784}\textbf{[GRE_rfc2784]} &
> > > +ÂÂÂ Generic Routing Encapsulation. This protocol is only specified
> > > for IPv4 and used as either the payload or delivery protocol.
> > > +ÂÂÂ \newline\url{https://datatracker.ietf.org/doc/rfc2784/}\\
> > > + \phantomsection\label{intro:gre_rfc2890}\textbf{[GRE_rfc2890]} &
> > > +ÂÂÂ Key and Sequence Number Extensions to GRE
> > > \ref{intro:gre_rfc2784}. This protocol describes extensions by which
> > > two fields, Key and
> > > +ÂÂÂ Sequence Number, can be optionally carried in the GRE Header
> > > \ref{intro:gre_rfc2784}.
> > > +ÂÂÂ \newline\url{https://www.rfc-editor.org/rfc/rfc2890}\\
> > > + \phantomsection\label{intro:gre_rfc7676}\textbf{[GRE_rfc7676]} &
> > > +ÂÂÂ IPv6 Support for Generic Routing Encapsulation (GRE). This
> > > protocol is specified for IPv6 and used as either the payload or
> > > +ÂÂÂ delivery protocol. Note that this does not change the GRE
> > > header format or any behaviors specified by RFC 2784 or RFC 2890.
> > > +ÂÂÂ \newline\url{https://datatracker.ietf.org/doc/rfc7676/}\\
> > > + \phantomsection\label{intro:gre_in_udp_rfc8086}\textbf{[GRE-in-UDP]} &
> > > +ÂÂÂ GRE-in-UDP Encapsulation. This specifies a method of
> > > encapsulating network protocol packets within GRE and UDP headers.
> > > +ÂÂÂ This GRE-in-UDP encapsulation allows the UDP source port field
> > > to be used as an entropy field. This protocol is specified for IPv4
> > > and IPv6,
> > > +ÂÂÂ and used as either the payload or delivery protocol.
> > > +ÂÂÂ \newline\url{https://www.rfc-editor.org/rfc/rfc8086}\\
> > > +ÂÂÂ \phantomsection\label{intro:vxlan}\textbf{[VXLAN]} &
> > > +ÂÂÂ Virtual eXtensible Local Area Network.
> > > +ÂÂÂ \newline\url{https://datatracker.ietf.org/doc/rfc7348/}\\
> > > +ÂÂÂ \phantomsection\label{intro:vxlan-gpe}\textbf{[VXLAN-GPE]} &
> > > +ÂÂÂ Generic Protocol Extension for VXLAN. This protocol describes
> > > extending Virtual eXtensible Local Area Network (VXLAN) via changes
> > > to the VXLAN header.
> > > + \newline\url{https://www.ietf.org/archive/id/draft-ietf-nvo3-vxlan-gpe-12.txt}\\
> > > +ÂÂÂ \phantomsection\label{intro:geneve}\textbf{[GENEVE]} &
> > > +ÂÂÂ Generic Network Virtualization Encapsulation.
> > > +ÂÂÂ \newline\url{https://datatracker.ietf.org/doc/rfc8926/}\\
> > > +ÂÂÂ \phantomsection\label{intro:ipip}\textbf{[IPIP]} &
> > > +ÂÂÂ IP Encapsulation within IP.
> > > +ÂÂÂ \newline\url{https://www.rfc-editor.org/rfc/rfc2003}\\
> > > +ÂÂÂ \phantomsection\label{intro:nvgre}\textbf{[NVGRE]} &
> > > +ÂÂÂ NVGRE: Network Virtualization Using Generic Routing Encapsulation
> > > +ÂÂÂ \newline\url{https://www.rfc-editor.org/rfc/rfc7637.html}\\
> > > +ÂÂÂ \phantomsection\label{intro:IP}\textbf{[IP]} &
> > > +ÂÂÂ INTERNET PROTOCOL
> > > +ÂÂÂ \newline\url{https://www.rfc-editor.org/rfc/rfc791}\\
> > > +ÂÂÂ \phantomsection\label{intro:UDP}\textbf{[UDP]} &
> > > +ÂÂÂ User Datagram Protocol
> > > +ÂÂÂ \newline\url{https://www.rfc-editor.org/rfc/rfc768}\\
> > > +ÂÂÂ \phantomsection\label{intro:TCP}\textbf{[TCP]} &
> > > +ÂÂÂ TRANSMISSION CONTROL PROTOCOL
> > > +ÂÂÂ \newline\url{https://www.rfc-editor.org/rfc/rfc793}\\
> > > Â \end{longtable}
> > > Â Â \section{Non-Normative References}
> > 
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