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Subject: Re: [virtio-dev] Re: [PATCH v2] virtio_net: support inner header hash for GRE-encapsulated packets
On Mon, Nov 28, 2022 at 1:33 PM Heng Qi <hengqi@linux.alibaba.com> wrote:
>
> On Mon, Nov 28, 2022 at 11:52:23AM +0800, Jason Wang wrote:
> >
> > å 2022/11/28 11:14, Heng Qi åé:
> > >On Fri, Nov 25, 2022 at 12:16:05PM +0800, Jason Wang wrote:
> > >>On Tue, Nov 22, 2022 at 5:08 PM Heng Qi <hengqi@linux.alibaba.com> wrote:
> > >>>When VIRTIO_NET_F_RSS is negotiated and the tunnel is used to
> > >>>encapsulate the packets, the hash calculated using the outer header
> > >>>of the receive packets is always fixed for the same flow packets,
> > >>>i.e. they will be steered to the same receive queue.
> > >>>
> > >>>We add a VIRTIO_NET_HASH_TYPE_GRE_INNER bitmask in \field{hash_types},
> > >>>which instructs the device to calculate the hash using the inner
> > >>>headers of GRE-encapsulated packets, and a VIRTIO_NET_HASH_REPORT_GRE
> > >>>value in \field{hash_tunnel} to report packet type when calculating
> > >>>hash over the inner header.
> > >>So I think we need a new feature bit for this to keep migration compatibility.
> > >>
> > >If we consider adding feature negotiation for this, it will be explained
> > >more below.
> > >
> > >>>Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> > >>>Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > >>>---
> > >>>v1:
> > >>> 1. Remove the patch for the bitmask fix. @Michael S. Tsirkin
> > >>> 2. Clarify some paragraphs. @Jason Wang
> > >>> 3. Add \field{hash_tunnel} and VIRTIO_NET_HASH_REPORT_GRE. @Yuri Benditovich
> > >>>
> > >>> content.tex | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++--
> > >>> 1 file changed, 135 insertions(+), 5 deletions(-)
> > >>>
> > >>>diff --git a/content.tex b/content.tex
> > >>>index e863709..fba0c7d 100644
> > >>>--- a/content.tex
> > >>>+++ b/content.tex
> > >>>@@ -3095,7 +3095,7 @@ \subsection{Feature bits}\label{sec:Device Types / Network Device / Feature bits
> > >>> to several segments when each of these smaller packets has UDP header.
> > >>>
> > >>> \item[VIRTIO_NET_F_HASH_REPORT(57)] Device can report per-packet hash
> > >>>- value and a type of calculated hash.
> > >>>+ value, a type of calculated hash and a tunnel packet type.
> > >>>
> > >>> \item[VIRTIO_NET_F_GUEST_HDRLEN(59)] Driver can provide the exact \field{hdr_len}
> > >>> value. Device benefits from knowing the exact header length.
> > >>>@@ -3386,7 +3386,8 @@ \subsection{Device Operation}\label{sec:Device Types / Network Device / Device O
> > >>> le16 num_buffers;
> > >>> le32 hash_value; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
> > >>> le16 hash_report; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
> > >>>- le16 padding_reserved; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
> > >>>+ le8 hash_tunnel; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
> > >>It's better not limit this to be tunnel only unless we limit the same
> > >>for hash_config.
> > >Maybe we can use the \field{hash_report_ex} instead of \field{hash_tunnel}ï
> >
> >
> > Probably.
> >
> >
> > >
> > >>Btw, this needs an independent fix. I wonder if we need a dedicated
> > >>feature bit VIRTIO_NET_F_HASH_REPORT_EX and documenting that device
> > >>SHOULD offer HASH_REPORT_EX along with HASH_REPORT. Then we can do GRE
> > >>tunnel hash report on top? (Or doing GRE first and fix the mismatch on
> > >>top)
> > >>
> > >For this, we have the following ideas:
> > >
> > >1. Considering our actual business application scenarios, the current mainstream
> > > tunnel-encapsulated technologies are mainly GRE and VXLAN, so we are also
> > > working on VXLAN.
> > >
> > >2. To keep migration compatibility, we can add a VIRTIO_NET_F_HASH_GRE_INNER
> > > feature bit (it depends on VIRTIO_NET_F_RSS). If it is negotiated, this
> > > means that the device calculates the hash based on the inner header of the
> > > GRE-encapsulated packet. We assume that the inner header in GRE is TCPv4,
> > > at this time \field{hash_types} needs to include
> > > (VIRTIO_NET_HASH_TYPE_GRE_INNER | VIRTIO_NET_HASH_TYPE_TCPv4). Besides,
> > > if VIRTIO_NET_F_HASH_REPORT is also negotiated, then \field{hash_report}
> > > should be set to VIRTIO_NET_HASH_REPORT_TCPv4, and field \field{hash_report_ex}
> > > should be set to VIRTIO_NET_HASH_REPORT_GRE.
> >
> >
> > One question here, if I was not wrong, hash_report is sufficient for
> > GRE and VXLAN now. So that's why I think they should be indenepent
> > patch.
> >
>
> As discussed in https://lists.oasis-open.org/archives/virtio-dev/202211/msg00064.html,
> \field{hash_report} is an integer rather than a bitmask.
Ok, I see.
> On the premise that
> VIRTIO_NET_F_HASH_GRE_INNER is negotiated, assuming that the inner header of the GRE packet
> is TCPv4 and we only have \field{hash_report} instead of \field{hash_report_ex}, then we
> need to set VIRTIO_NET_HASH_REPORT_GRE(10) in \field{hash_report} along with
> VIRTIO_NET_HASH_REPORT_TCPv4(2). At this point \field{hash_report} should be (2+10=12).
>
> However, if the inner header of another VXLAN packet is IPv4, and VIRTIO_NET_HASH_REPORT_VXLAN
> is 11 (following VIRTIO_NET_HASH_REPORT_GRE(10), like below), then \field{hash_report} is
> (1+11=12). Then how does the driver distinguish that 12 belongs to the above which situation?
>
> Suppose the report type is as follows:
> \begin{lstlisting}
> #define VIRTIO_NET_HASH_REPORT_NONE 0
> #define VIRTIO_NET_HASH_REPORT_IPv4 1
> #define VIRTIO_NET_HASH_REPORT_TCPv4 2
> #define VIRTIO_NET_HASH_REPORT_UDPv4 3
> #define VIRTIO_NET_HASH_REPORT_IPv6 4
> #define VIRTIO_NET_HASH_REPORT_TCPv6 5
> #define VIRTIO_NET_HASH_REPORT_UDPv6 6
> #define VIRTIO_NET_HASH_REPORT_IPv6_EX 7
> #define VIRTIO_NET_HASH_REPORT_TCPv6_EX 8
> #define VIRTIO_NET_HASH_REPORT_UDPv6_EX 9
> #define VIRTIO_NET_HASH_REPORT_GRE 10
> #define VIRTIO_NET_HASH_REPORT_VXLAN 11
> \end{lstlisting}
>
> So it seems more reasonable to include tunnel-related report types in \field{hash_report_ex},
Ok, I think I got this, if we go this way, hash_report_tunnel might be better.
In the long run, the mismatching behaviour of hash_config and
hash_report might end up more burden in the maintenance. I wonder if
it's worth it to make hash_report a bitmask that matches hash_config.
That seems to ease everything a lot.
Thanks
> or we can adopt something like https://lists.oasis-open.org/archives/virtio-dev/202211/msg00064.html
> , which only uses the \field{hash_report} method.
>
> >
> > >
> > >3. Why don't we consider a feature bit for all tunnel types?
> > >
> > > If some devices do not support GRE but support VXLAN, and some devices
> > > support both VXLAN and GRE, so we must set the specific feature bit
> > > (e.g VIRTIO_NET_F_HASH_GRE_INNER) for a specific tunnel type. Fortunately,
> > > the number of mainstream tunnel encapsulations is limited.
> >
> >
> > My understanding is that if we start from having both GRE and VXLAN
> > for a single feature bit, it would be simpler for both maintaining
> > (spec), driver and device(vendor).
> >
> > (E.g it can force the device vendor to implement both)
>
> Ok, this seems to work. We can bind them together.
>
> >
> >
> > >
> > >4. Why do we not need VIRTIO_NET_F_HASH_REPORT_EX after we negotiate VIRTIO_NET_F_HASH_GRE_INNER?
> > >
> > > Because once VIRTIO_NET_F_HASH_GRE_INNER is negotiated, the device should
> > > calculate the hash based on the GRE inner header, and should not hide the
> > > information when reporting, that is, VIRTIO_NET_HASH_REPORT_TCPv4 and
> > > VIRTIO_NET_HASH_REPORT_GRE should be set in \field{hash_report} and
> > > \field{hash_report_ex} respectively.
> > >
> > >Do you think this is feasible?
> >
> >
> > I think so.
> >
> >
> > >
> > >>>+ le8 padding_reserved; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
> > >>> };
> > >>> \end{lstlisting}
> > >>>
> > >>>@@ -3837,7 +3838,7 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > >>> A device attempts to calculate a per-packet hash in the following cases:
> > >>> \begin{itemize}
> > >>> \item The feature VIRTIO_NET_F_RSS was negotiated. The device uses the hash to determine the receive virtqueue to place incoming packets.
> > >>>-\item The feature VIRTIO_NET_F_HASH_REPORT was negotiated. The device reports the hash value and the hash type with the packet.
> > >>>+\item The feature VIRTIO_NET_F_HASH_REPORT was negotiated. The device reports the hash value, the hash type and the tunnel packet type.
> > >>> \end{itemize}
> > >>>
> > >>> If the feature VIRTIO_NET_F_RSS was negotiated:
> > >>>@@ -3883,6 +3884,10 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > >>> #define VIRTIO_NET_HASH_TYPE_TCP_EX (1 << 7)
> > >>> #define VIRTIO_NET_HASH_TYPE_UDP_EX (1 << 8)
> > >>> \end{lstlisting}
> > >>>+Hash types applicable to inner payloads of GRE-encapsulated packets
> > >>Unless there are other GRE related hash types, would it be better to
> > >>say "inner payloads of tunnel packets"?
> > >>
> > >We will post a similar spec for VXLAN-encapsulated packets, which is in
> > >process. It is also a tunnel hash type.
> > >
> > >>>+\begin{lstlisting}
> > >>>+#define VIRTIO_NET_HASH_TYPE_GRE_INNER (1 << 9)
> > >>>+\end{lstlisting}
> > >>>
> > >>> \subparagraph{IPv4 packets}
> > >>> \label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / IPv4 packets}
> > >>>@@ -3975,12 +3980,123 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > >>> (see \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / IPv6 packets without extension header}).
> > >>> \end{itemize}
> > >>>
> > >>>+\subparagraph{Inner payloads of GRE-encapsulated packets}
> > >>>+\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Inner payloads of GRE-encapsulated packets}}
> > >>>+VIRTIO_NET_HASH_TYPE_GRE_INNER bit is set at the same time as one of
> > >>>+the bits between VIRTIO_NET_HASH_TYPE_IPv4 and VIRTIO_NET_HASH_TYPE_UDP_EX.
> > >>>+
> > >>>+The device calculates the hash on GRE-encapsulated packets whose inner payloads
> > >>>+are IPv4 packets according to 'Enabled hash types' bitmasks as follows:
> > >>>+\begin{itemize}
> > >>>+ \item If both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_TCPv4 bits
> > >>>+ are set, and the GRE-encapsulated packet has an inner TCPv4 header in its
> > >>>+ payload, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item inner Source IP address
> > >>>+ \item inner Destination IP address
> > >>>+ \item inner Source TCP port
> > >>>+ \item inner Destination TCP port
> > >>>+ \end{itemsize}
> > >>>+ \item Else if both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_UDPv4
> > >>>+ bits are set, and the GRE-encapsulated packet has an inner UDPv4 header in
> > >>>+ its payload, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item inner Source IP address
> > >>>+ \item inner Destination IP address
> > >>>+ \item inner Source UDP port
> > >>>+ \item inner Destination UDP port
> > >>>+ \end{itemize}
> > >>>+ \item Else if both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_IPv4
> > >>>+ bits are set, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item inner Source IP address
> > >>>+ \item inner Destination IP address
> > >>>+ \end{itemsize}
> > >>>+ \item Else the device does not calculate the hash
> > >>>+\end{itemize}
> > >>>+
> > >>>+The device calculates the hash on GRE-encapsulated packets whose inner payloads
> > >>>+are IPv6 packets without extension headers according to 'Enabled hash types'
> > >>>+bitmasks as follows:
> > >>>+\begin{itemsize}
> > >>>+ \item If both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_TCPv6
> > >>>+ bits are set, and the GRE-encapsulated packet has an inner TCPv6 header in
> > >>>+ its payload, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item inner Source IPv6 address
> > >>>+ \item inner Destination IPv6 address
> > >>>+ \item inner Source TCP port
> > >>>+ \item inner Destination TCP port
> > >>>+ \end{itemsize}
> > >>>+ \item Else if both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_UDPv6
> > >>>+ bits are set, and the GRE-encapsulated packet has an inner UDPv6 header in
> > >>>+ its payload, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item inner Source IPv6 address
> > >>>+ \item inner Destination IPv6 address
> > >>>+ \item inner Source UDP port
> > >>>+ \item inner Destination UDP port
> > >>>+ \end{itemize}
> > >>>+ \item Else if both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_IPv6
> > >>>+ bits are set, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item inner Source IPv6 address
> > >>>+ \item inner Destination IPv6 address
> > >>>+ \end{itemsize}
> > >>>+ \item Else the device does not calculate the hash
> > >>>+\end{itemize}
> > >>>+
> > >>>+The device calculates the hash on GRE-encapsulated packets whose inner payloads
> > >>>+are IPv6 packets with extension headers according to 'Enabled hash types'
> > >>>+bitmasks as follows:
> > >>>+\begin{itemsize}
> > >>>+ \item If both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_TCP_EX
> > >>>+ bits are set, and the GRE-encapsulated packet has an inner TCPv6 header in
> > >>>+ its payload, the hash is calculated over the following fields:
> > >>>+ \begin{itemize}
> > >>>+ \item Home address from the home address option in the inner IPv6 destination
> > >>>+ options header. If the inner extension header is not present, use the
> > >>>+ inner Source IPv6 address.
> > >>>+ \item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > >>>+ associated inner extension header. If the inner extension header is not
> > >>>+ present, use the inner Destination IPv6 address.
> > >>>+ \item inner Source TCP port
> > >>>+ \item inner Destination TCP port
> > >>>+ \end{itemize}
> > >>>+ \item Else if both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_UDP_EX
> > >>>+ bits are set, and the GRE-encapsulated packet has an inner UDPv6 header in its
> > >>>+ payload, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item Home address from the home address option in the inner IPv6 destination
> > >>>+ options header. If the inner extension header is not present, use the
> > >>>+ inner Source IPv6 address.
> > >>>+ \item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > >>>+ associated inner extension header. If the inner extension header is not
> > >>>+ present, use the inner Destination IPv6 address.
> > >>>+ \item inner Source UDP port
> > >>>+ \item inner Destination UDP port
> > >>>+ \end{itemize}
> > >>>+ \item Else if both VIRTIO_NET_HASH_TYPE_GRE_INNER and VIRTIO_NET_HASH_TYPE_IP_EX
> > >>>+ bits are set, the hash is calculated over the following fields:
> > >>>+ \begin{itemsize}
> > >>>+ \item Home address from the home address option in the inner IPv6 destination
> > >>>+ options header. If the inner extension header is not present, use the
> > >>>+ inner Source IPv6 address.
> > >>>+ \item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > >>>+ associated inner extension header. If the inner extension header is not
> > >>>+ present, use the inner Destination IPv6 address.
> > >>>+ \end{itemize}
> > >>>+ \item Else skip inner IPv6 extension headers and calculate the hash as defined
> > >>>+ for a GRE-encapsulated packet whose inner payload is an IPv6 packet without
> > >>>+ extension headers
> > >>>+\end{itemsize}
> > >>>+
> > >>> \paragraph{Hash reporting for incoming packets}
> > >>> \label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash reporting for incoming packets}
> > >>>
> > >>> If VIRTIO_NET_F_HASH_REPORT was negotiated and
> > >>>- the device has calculated the hash for the packet, the device fills \field{hash_report} with the report type of calculated hash
> > >>>-and \field{hash_value} with the value of calculated hash.
> > >>>+ the device has calculated the hash for the packet, the device fills \field{hash_report} with the report type of calculated hash,
> > >>>+\field{hash_tunnel} with the type of the tunnel packet, and \field{hash_value} with the value of calculated hash.
> > >>>
> > >>> If VIRTIO_NET_F_HASH_REPORT was negotiated but due to any reason the
> > >>> hash was not calculated, the device sets \field{hash_report} to VIRTIO_NET_HASH_REPORT_NONE.
> > >>>@@ -4005,6 +4121,20 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> > >>> #define VIRTIO_NET_HASH_REPORT_UDPv6_EX 9
> > >>> \end{lstlisting}
> > >>>
> > >>>+If \field{hash_report} differs from VIRTIO_NET_HASH_REPORT_NONE,
> > >>>+\field{hash_tunnel} can report the type of the tunnel-encapsulated
> > >>>+packet to the driver over the inner header hash calculation.
> > >>>+Possible values that the device can report in field{hash_tunnel}
> > >>>+are defined below:
> > >>>+
> > >>>+\begin{lstlisting}
> > >>>+#define VIRTIO_NET_HASH_REPORT_GRE 1
> > >>>+\end{lstlisting}
> > >>What's the advantage of not simply doing the matching via the existing math:
> > >>
> > >>VIRTIO_NET_HASH_TYPE_XXX = 1 Â (VIRTIO_NET_HASH_REPORT_XXX - 1)
> > >>?
> > >>
> > >Considering that other tunnel-encapsulated packets may be added, this
> > >existing formula will no longer be applicable.
> >
> >
> > So I basically mean what's wrong with simply defining
> > VIRTIO_NET_HASH_TYPE_GRE_INNER as 10?
> >
>
> Considering the addition of VXLAN, if VIRTIO_NET_HASH_TYPE_GRE_INNER is 10,
> then VIRTIO_NET_HASH_TYPE_VXLAN_INNER should be 11, and they need to be
> used with existing types in \field{hash_report} which brings problems as I
> explained above, since they are integers instead of bitmask.
>
> Thanks.
>
> > Thanks
> >
> >
> > >
> > >Thanks.
> > >
> > >>Thanks
> > >>
> > >>
> > >>>+
> > >>>+The value VIRTIO_NET_HASH_REPORT_GRE corresponds to
> > >>>+VIRTIO_NET_HASH_TYPE_GRE_INNER bit of supported hash types defined in
> > >>>+\ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash types}.
> > >>>+
> > >>> \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue}
> > >>>
> > >>> The driver uses the control virtqueue (if VIRTIO_NET_F_CTRL_VQ is
> > >>>--
> > >>>2.19.1.6.gb485710b
> > >>>
> > >>
> > >>---------------------------------------------------------------------
> > >>To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org
> > >>For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
>
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