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Subject: Re: [PATCH v16] virtio-net: support inner header hash
On Sun, Jun 11, 2023 at 08:13:58PM +0000, Parav Pandit wrote:
>
> > From: Heng Qi <hengqi@linux.alibaba.com>
> > Sent: Saturday, June 10, 2023 12:11 AM
>
> > +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 driver.
> Driver issues set command so its read + write for driver.
> Read-only for the device.
This is talking about buffers I think. These are read-only or
write-only, there is no read+write.
> > +\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
> > + structure, which is write-only for the driver.
> Device writes it, so
> s/write-only for the driver/read-only for the driver
Please use terminology consistent with how we describe buffers,
which is from POV of the device. Thus buffers are
device read-only or device write-only.
> > +\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 \hyperref[intro:gre_rfc2784]{[GRE_rfc2784]}: the outer header is over
> > IPv4 and the inner header is over IPv4. The outer header does not contain the
> > transport protocol.
> > +\item \hyperref[intro:gre_rfc2890]{[GRE_rfc2890]}: the outer header is over
> > IPv4 and the inner header is over IPv4. The outer header does not contain the
> > transport protocol.
> > +\item \hyperref[intro:gre_rfc7676]{[GRE_rfc7676]}: the outer header is over
> > IPv4/IPv6 and the inner header is over IPv4/IPv6. The outer header does not
> > contain the transport protocol.
> > +\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. The outer header uses
> > UDP as the transport protocol.
> > +\item \hyperref[intro:vxlan]{[VXLAN]}: the outer header is over IPv4/IPv6 and
> > the inner header is over IPv4/IPv6. The outer header uses UDP as the transport
> > protocol.
> > +\item \hyperref[intro:vxlan_gpe]{[VXLAN-GPE]}: the outer header is over
> > IPv4/IPv6 and the inner header is over IPv4/IPv6. The outer header uses UDP as
> > the transport protocol.
> > +\item \hyperref[intro:geneve]{[GENEVE]}: the outer header is over IPv4/IPv6
> > and the inner header is over IPv4/IPv6. The outer header uses UDP as the
> > transport protocol.
> > +\item \hyperref[intro:ipip]{[IPIP]}: the outer header is over IPv4 and the inner
> > header is over IPv4. The outer header does not contain the transport protocol.
> > +\item \hyperref[intro:nvgre]{[NVGRE]}: the outer header is over IPv4/IPv6 and
> > the inner header is over IPv4/IPv6. The outer header does not contain the
> > transport protocol.
> > +\end{itemize}
> > +
> It does not matter much, but it may be good to arrange above list where all entries that does not have transport header first.
> And than protocols with transport header together (vxlan-gpe, genve, nvgre).
>
> > +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_NONE (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_2784 (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_2890 (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_7676 (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_UDP (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_VXLAN (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_GPE (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_GENEVE (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_IPIP (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_NVGRE (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
> > + 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,
>
> > + warm caches, lessing locking, etc. are optimized to obtain receiving
> > performance.
> > +\end{itemize}
> > +
> Small rewrite as,
> to utilize warm caches, to have less locking etc.
>
> > +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 filling up.
> Generally filling up is fine as long as its emptied also.
> So a rewrite as,
>
> s/from filling up/from dropping packet/
>
> > +\item If the QoS is unavailable, the driver can set \field{hash_tunnel_types} to
> > VIRTIO_NET_HASH_TUNNEL_TYPE_NONE
> > + 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.
> > +
> > \paragraph{Hash reporting for incoming packets} \label{sec:Device Types /
> > Network Device / Device Operation / Processing of Incoming Packets / Hash
> > reporting for incoming packets}
> >
> > 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 @@
> > \item \ref{devicenormative:Device Types / Network Device / Device Operation
> > / Control Virtqueue / Automatic receive steering in multiqueue mode} \item
> > \ref{devicenormative:Device Types / Network Device / Device Operation /
> > Control Virtqueue / Receive-side scaling (RSS) / RSS processing} \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}
> > \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 @@
> > \item \ref{drivernormative:Device Types / Network Device / Device Operation
> > / Control Virtqueue / Offloads State Configuration / Setting Offloads State}
> > \item \ref{drivernormative:Device Types / Network Device / Device Operation /
> > Control Virtqueue / Receive-side scaling (RSS) } \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}
> > \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}
> > Standards for Efficient Cryptography Group(SECG), ``SEC1: Elliptic Cureve
> > Cryptography'', Version 1.0, September 2000.
> > \newline\url{https://www.secg.org/sec1-v2.pdf}\\
> >
> > + \phantomsection\label{intro:gre_rfc2784}\textbf{[GRE_rfc2784]} &
> > + Generic Routing Encapsulation. This protocol is only specified for IPv4 and
> > used as either the payload or delivery protocol.
> > + \newline\url{https://datatracker.ietf.org/doc/rfc2784/}\\
> > + \phantomsection\label{intro:gre_rfc2890}\textbf{[GRE_rfc2890]} &
> > + Key and Sequence Number Extensions to GRE \ref{intro:gre_rfc2784}. This
> > protocol describes extensions by which two fields, Key and
> > + Sequence Number, can be optionally carried in the GRE Header
> > \ref{intro:gre_rfc2784}.
> > + \newline\url{https://www.rfc-editor.org/rfc/rfc2890}\\
> > + \phantomsection\label{intro:gre_rfc7676}\textbf{[GRE_rfc7676]} &
> > + IPv6 Support for Generic Routing Encapsulation (GRE). This protocol is
> > specified for IPv6 and used as either the payload or
> > + delivery protocol. Note that this does not change the GRE header format or
> > any behaviors specified by RFC 2784 or RFC 2890.
> > + \newline\url{https://datatracker.ietf.org/doc/rfc7676/}\\
> > + \phantomsection\label{intro:gre_in_udp_rfc8086}\textbf{[GRE-in-UDP]}
> > &
> > + GRE-in-UDP Encapsulation. This specifies a method of encapsulating
> > network protocol packets within GRE and UDP headers.
> > + 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,
> > + and used as either the payload or delivery protocol.
> > + \newline\url{https://www.rfc-editor.org/rfc/rfc8086}\\
> > + \phantomsection\label{intro:vxlan}\textbf{[VXLAN]} &
> > + Virtual eXtensible Local Area Network.
> > + \newline\url{https://datatracker.ietf.org/doc/rfc7348/}\\
> > + \phantomsection\label{intro:vxlan-gpe}\textbf{[VXLAN-GPE]} &
> > + 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}\\
> > + \phantomsection\label{intro:geneve}\textbf{[GENEVE]} &
> > + Generic Network Virtualization Encapsulation.
> > + \newline\url{https://datatracker.ietf.org/doc/rfc8926/}\\
> > + \phantomsection\label{intro:ipip}\textbf{[IPIP]} &
> > + IP Encapsulation within IP.
> > + \newline\url{https://www.rfc-editor.org/rfc/rfc2003}\\
> > + \phantomsection\label{intro:nvgre}\textbf{[NVGRE]} &
> > + NVGRE: Network Virtualization Using Generic Routing Encapsulation
> > + \newline\url{https://www.rfc-editor.org/rfc/rfc7637.html}\\
> > + \phantomsection\label{intro:IP}\textbf{[IP]} &
> > + INTERNET PROTOCOL
> > + \newline\url{https://www.rfc-editor.org/rfc/rfc791}\\
> > + \phantomsection\label{intro:UDP}\textbf{[UDP]} &
> > + User Datagram Protocol
> > + \newline\url{https://www.rfc-editor.org/rfc/rfc768}\\
> > + \phantomsection\label{intro:TCP}\textbf{[TCP]} &
> > + TRANSMISSION CONTROL PROTOCOL
> > + \newline\url{https://www.rfc-editor.org/rfc/rfc793}\\
> > \end{longtable}
> >
> > \section{Non-Normative References}
> > --
> > 2.19.1.6.gb485710b
>
> With above small fixes,
> Reviewed-by: Parav Pandit <parav@nvidia.com>
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