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Subject: [PATCH v2] virtio-net: Define per-packet hash reporting feature
Fixes: https://github.com/oasis-tcs/virtio-spec/issues/66
Define respective feature bit for virtio-net.
Extend packet layout to populate hash value and type.
Move the definition of IP/TCP/UDP header fields to
calculate the hash out of RSS section to common network
device section.
Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>
---
content.tex | 299 ++++++++++++++++++++++++++++++++--------------------
1 file changed, 184 insertions(+), 115 deletions(-)
diff --git a/content.tex b/content.tex
index fb10061..2836e0a 100644
--- a/content.tex
+++ b/content.tex
@@ -2895,6 +2895,9 @@ \subsection{Feature bits}\label{sec:Device Types / Network Device / Feature bits
\item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control
channel.
+\item[VIRTIO_NET_F_HASH_REPORT(58)] Device can report per-packet hash
+ value and a type of calculated hash.
+
\item[VIRTIO_NET_F_GUEST_HDRLEN(59)] Driver can provide the exact \field{hdr_len}
value. Device benefits from knowing the exact header length.
@@ -2981,35 +2984,18 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
le32 supported_hash_types;
};
\end{lstlisting}
-\label{sec:Device Types / Network Device / Device configuration layout / RSS}
-Three following fields, \field{rss_max_key_size}, \field{rss_max_indirection_table_length}
-and \field{supported_hash_types} only exist if VIRTIO_NET_F_RSS is set.
+Two following fields, \field{rss_max_key_size} and \field{rss_max_indirection_table_length}
+only exist if VIRTIO_NET_F_RSS is set.
Field \field{rss_max_key_size} specifies the maximal supported length of RSS key in bytes.
Field \field{rss_max_indirection_table_length} specifies the maximal number of 16-bit entries in RSS indirection table.
-Field \field{supported_hash_types} contains the bitmask of supported RSS hash types.
+The next field, \field{supported_hash_types} exists only if the device supports hash calculation,
+i.e. suggests VIRTIO_NET_F_HASH_REPORT or VIRTIO_NET_F_RSS.
-Hash types applicable for IPv4 packets:
-\begin{lstlisting}
-#define VIRTIO_NET_RSS_HASH_TYPE_IPv4 (1 << 0)
-#define VIRTIO_NET_RSS_HASH_TYPE_TCPv4 (1 << 1)
-#define VIRTIO_NET_RSS_HASH_TYPE_UDPv4 (1 << 2)
-\end{lstlisting}
-Hash types applicable for IPv6 packets without extension headers
-\begin{lstlisting}
-#define VIRTIO_NET_RSS_HASH_TYPE_IPv6 (1 << 3)
-#define VIRTIO_NET_RSS_HASH_TYPE_TCPv6 (1 << 4)
-#define VIRTIO_NET_RSS_HASH_TYPE_UDPv6 (1 << 5)
-\end{lstlisting}
-Hash types applicable for IPv6 packets with extension headers
-\begin{lstlisting}
-#define VIRTIO_NET_RSS_HASH_TYPE_IP_EX (1 << 6)
-#define VIRTIO_NET_RSS_HASH_TYPE_TCP_EX (1 << 7)
-#define VIRTIO_NET_RSS_HASH_TYPE_UDP_EX (1 << 8)
-\end{lstlisting}
-For the exact meaning of VIRTIO_NET_RSS_HASH_TYPE_ flags see \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS hash types}.
+Field \field{supported_hash_types} contains the bitmask of supported hash types.
+See \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash types} for details of supported hash types.
\devicenormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout}
@@ -3159,6 +3145,8 @@ \subsection{Device Operation}\label{sec:Device Types / Network Device / Device O
le16 csum_start;
le16 csum_offset;
le16 num_buffers;
+ le32 hash_value; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
+ le16 hash_type; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
};
\end{lstlisting}
@@ -3481,6 +3469,12 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
\end{enumerate}
+If applicable, the device calculates per-packet hash for incoming packets as
+defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets}.
+
+If applicable, the device reports hash information for incoming packets as
+defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash reporting for incoming packets}.
+
\devicenormative{\paragraph}{Processing of Incoming Packets}{Device Types / Network Device / Device Operation / Processing of Incoming Packets}
\label{devicenormative:Device Types / Network Device / Device Operation / Processing of Packets}%old label for latexdiff
@@ -3583,6 +3577,168 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
If neither VIRTIO_NET_HDR_F_NEEDS_CSUM nor
VIRTIO_NET_HDR_F_DATA_VALID is set, the driver MUST NOT
rely on the packet checksum being correct.
+
+\paragraph{Hash calculation for incoming packets}
+\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets}
+
+A device attempts to calculate per-packet hash in following cases:
+\begin{itemize}
+\item The feature VIRTIO_NET_F_RSS was negotiated. The device uses the hash to determine receive virtqueue to place incoming packet to.
+\item The feature VIRTIO_NET_F_HASH_REPORT was negotiated. The device reports hash value and hash type with the packet.
+\end{itemize}
+
+If the feature VIRTIO_NET_F_RSS was negotiated:
+\begin{itemize}
+\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_key_data} of the virtio_net_rss_config structure.
+\end{itemize}
+See the definition of virtio_net_rss_config structure in \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / Setting RSS parameters}
+
+If the feature VIRTIO_NET_F_RSS was not negotiated, the device uses internal configuration
+of enabled hash types and a key used for hash calculation.
+
+\subparagraph{Supported/enabled hash types}
+\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash types}
+Hash types applicable for IPv4 packets:
+\begin{lstlisting}
+#define VIRTIO_NET_HASH_TYPE_IPv4 (1 << 0)
+#define VIRTIO_NET_HASH_TYPE_TCPv4 (1 << 1)
+#define VIRTIO_NET_HASH_TYPE_UDPv4 (1 << 2)
+\end{lstlisting}
+Hash types applicable for IPv6 packets without extension headers
+\begin{lstlisting}
+#define VIRTIO_NET_HASH_TYPE_IPv6 (1 << 3)
+#define VIRTIO_NET_HASH_TYPE_TCPv6 (1 << 4)
+#define VIRTIO_NET_HASH_TYPE_UDPv6 (1 << 5)
+\end{lstlisting}
+Hash types applicable for IPv6 packets with extension headers
+\begin{lstlisting}
+#define VIRTIO_NET_HASH_TYPE_IP_EX (1 << 6)
+#define VIRTIO_NET_HASH_TYPE_TCP_EX (1 << 7)
+#define VIRTIO_NET_HASH_TYPE_UDP_EX (1 << 8)
+\end{lstlisting}
+
+\subparagraph{IPv4 packets}
+\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / IPv4 packets}
+The device calculates the hash on IPv4 packets according to 'Enabled hash types' bitmask as follows:
+\begin{itemize}
+\item If VIRTIO_NET_HASH_TYPE_TCPv4 is set and the packet has
+a TCP header, the hash is calculated over the following fields:
+\begin{itemize}
+\item Source IP address
+\item Destination IP address
+\item Source TCP port
+\item Destination TCP port
+\end{itemize}
+\item Else if VIRTIO_NET_HASH_TYPE_UDPv4 is set and the
+packet has a UDP header, the hash is calculated over the following fields:
+\begin{itemize}
+\item Source IP address
+\item Destination IP address
+\item Source UDP port
+\item Destination UDP port
+\end{itemize}
+\item Else if VIRTIO_NET_HASH_TYPE_IPv4 is set, the hash is
+calculated over the following fields:
+\begin{itemize}
+\item Source IP address
+\item Destination IP address
+\end{itemize}
+\item Else the device does not calculate the hash
+\end{itemize}
+
+\subparagraph{IPv6 packets without extension header}
+\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / IPv6 packets without extension header}
+The device calculates the hash on IPv6 packets without extension
+headers to 'Enabled hash types' bitmask as follows:
+\begin{itemize}
+\item If VIRTIO_NET_HASH_TYPE_TCPv6 is set and the packet has
+a TCPv6 header, the hash is calculated over the following fields:
+\begin{itemize}
+\item Source IPv6 address
+\item Destination IPv6 address
+\item Source TCP port
+\item Destination TCP port
+\end{itemize}
+\item Else if VIRTIO_NET_HASH_TYPE_UDPv6 is set and the
+packet has a UDPv6 header, the hash is calculated over the following fields:
+\begin{itemize}
+\item Source IPv6 address
+\item Destination IPv6 address
+\item Source UDP port
+\item Destination UDP port
+\end{itemize}
+\item Else if VIRTIO_NET_HASH_TYPE_IPv6 is set, the hash is
+calculated over the following fields:
+\begin{itemize}
+\item Source IPv6 address
+\item Destination IPv6 address
+\end{itemize}
+\item Else the device does not calculate the hash
+\end{itemize}
+
+\subparagraph{IPv6 packets with extension header}
+\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / IPv6 packets with extension header}
+The device calculates the hash on IPv6 packets with extension
+headers according to to 'Enabled hash types' bitmask as follows:
+\begin{itemize}
+\item If VIRTIO_NET_HASH_TYPE_TCP_EX is set and the packet
+has a TCPv6 header, the hash is calculated over the following fields:
+\begin{itemize}
+\item Home address from the home address option in the IPv6 destination options header. If the extension header is not present, use the Source IPv6 address.
+\item IPv6 address that is contained in the Routing-Header-Type-2 from the associated extension header. If the extension header is not present, use the Destination IPv6 address.
+\item Source TCP port
+\item Destination TCP port
+\end{itemize}
+\item Else if VIRTIO_NET_HASH_TYPE_UDP_EX is set and the
+packet has a UDPv6 header, the hash is calculated over the following fields:
+\begin{itemize}
+\item Home address from the home address option in the IPv6 destination options header. If the extension header is not present, use the Source IPv6 address.
+\item IPv6 address that is contained in the Routing-Header-Type-2 from the associated extension header. If the extension header is not present, use the Destination IPv6 address.
+\item Source UDP port
+\item Destination UDP port
+\end{itemize}
+\item Else if VIRTIO_NET_HASH_TYPE_IP_EX is set, the hash is
+calculated over the following fields:
+\begin{itemize}
+\item Home address from the home address option in the IPv6 destination options header. If the extension header is not present, use the Source IPv6 address.
+\item IPv6 address that is contained in the Routing-Header-Type-2 from the associated extension header. If the extension header is not present, use the Destination IPv6 address.
+\end{itemize}
+\item Else skip IPv6 extension headers and calculate the hash as
+defined for an IPv6 packet without extension headers
+(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}
+
+\paragraph{Hash reporting for incoming packets}
+\label{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash reporting for incoming packets}%old label for latexdiff
+
+If feature VIRTIO_NET_F_HASH_REPORT was negotiated and
+ the device has calculated the hash for the packet, the device fills \field{hash_type} with the type of calculated hash
+and \field{hash_value} with the value of calculated hash.
+
+If VIRTIO_NET_F_HASH_REPORT was negotiated but due to any reason the
+has was not calculated, the device sets \field{hash_type} to VIRTIO_NET_HASH_REPORT_NONE.
+
+Possible values that the device can report in \field{hash_type} are defined below.
+They correspond to 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}
+as follows:
+
+VIRTIO_NET_HASH_TYPE_XXX = 1 << (VIRTIO_NET_HASH_REPORT_XXX - 1)
+
+\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
+\end{lstlisting}
+
\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
@@ -3928,7 +4084,7 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
\paragraph{Receive-side scaling (RSS)}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS)}
A device offers the feature VIRTIO_NET_F_RSS if it supports RSS receive steering with Toeplitz hash calculation and configurable parameters.
-A driver queries RSS capabilities of the device by reading device configuration as defined in \ref{sec:Device Types / Network Device / Device configuration layout / RSS}
+A driver queries RSS capabilities of the device by reading device configuration as defined in \ref{sec:Device Types / Network Device / Device configuration layout}
\subparagraph{Setting RSS parameters}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / Setting RSS parameters}
@@ -3945,7 +4101,8 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
};
\end{lstlisting}
Field \field{hash_types} contains a bitmask of allowed hash types as
-defined in \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS 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}.
Field \field{indirection_table_mask} is a mask to be applied to
the calculated hash to produce an index in the
@@ -3959,94 +4116,6 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
A driver sets \field{max_tx_vq} to inform a device how many transmit virtqueues it may use (transmitq1\ldots transmitq \field{max_tx_vq}).
-\subparagraph{RSS hash types}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS hash types}
-
-The device calculates the hash on IPv4 packets according to the
-field \field{hash_types} of the virtio_net_rss_config structure as follows:
-\begin{itemize}
-\item If VIRTIO_NET_RSS_HASH_TYPE_TCPv4 is set and the packet has
-a TCP header, the hash is calculated over the following fields:
-\begin{itemize}
-\item Source IP address
-\item Destination IP address
-\item Source TCP port
-\item Destination TCP port
-\end{itemize}
-\item Else if VIRTIO_NET_RSS_HASH_TYPE_UDPv4 is set and the
-packet has a UDP header, the hash is calculated over the following fields:
-\begin{itemize}
-\item Source IP address
-\item Destination IP address
-\item Source UDP port
-\item Destination UDP port
-\end{itemize}
-\item Else if VIRTIO_NET_RSS_HASH_TYPE_IPv4 is set, the hash is
-calculated over the following fields:
-\begin{itemize}
-\item Source IP address
-\item Destination IP address
-\end{itemize}
-\item Else the device does not calculate the hash
-\end{itemize}
-
-\label{itm:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS hash types/hash on IPv6 packets without extension headers}
-The device calculates the hash on IPv6 packets without extension
-headers according to the field \field{hash_types} of the virtio_net_rss_config structure as follows:
-\begin{itemize}
-\item If VIRTIO_NET_RSS_HASH_TYPE_TCPv6 is set and the packet has
-a TCPv6 header, the hash is calculated over the following fields:
-\begin{itemize}
-\item Source IPv6 address
-\item Destination IPv6 address
-\item Source TCP port
-\item Destination TCP port
-\end{itemize}
-\item Else if VIRTIO_NET_RSS_HASH_TYPE_UDPv6 is set and the
-packet has a UDPv6 header, the hash is calculated over the following fields:
-\begin{itemize}
-\item Source IPv6 address
-\item Destination IPv6 address
-\item Source UDP port
-\item Destination UDP port
-\end{itemize}
-\item Else if VIRTIO_NET_RSS_HASH_TYPE_IPv6 is set, the hash is
-calculated over the following fields:
-\begin{itemize}
-\item Source IPv6 address
-\item Destination IPv6 address
-\end{itemize}
-\item Else the device does not calculate the hash
-\end{itemize}
-
-The device calculates the hash on IPv6 packets with extension
-headers according to the field \field{hash_types} of the virtio_net_rss_config structure as follows:
-\begin{itemize}
-\item If VIRTIO_NET_RSS_HASH_TYPE_TCP_EX is set and the packet
-has a TCPv6 header, the hash is calculated over the following fields:
-\begin{itemize}
-\item Home address from the home address option in the IPv6 destination options header. If the extension header is not present, use the Source IPv6 address.
-\item IPv6 address that is contained in the Routing-Header-Type-2 from the associated extension header. If the extension header is not present, use the Destination IPv6 address.
-\item Source TCP port
-\item Destination TCP port
-\end{itemize}
-\item Else if VIRTIO_NET_RSS_HASH_TYPE_UDP_EX is set and the
-packet has a UDPv6 header, the hash is calculated over the following fields:
-\begin{itemize}
-\item Home address from the home address option in the IPv6 destination options header. If the extension header is not present, use the Source IPv6 address.
-\item IPv6 address that is contained in the Routing-Header-Type-2 from the associated extension header. If the extension header is not present, use the Destination IPv6 address.
-\item Source UDP port
-\item Destination UDP port
-\end{itemize}
-\item Else if VIRTIO_NET_RSS_HASH_TYPE_IP_EX is set, the hash is
-calculated over the following fields:
-\begin{itemize}
-\item Home address from the home address option in the IPv6 destination options header. If the extension header is not present, use the Source IPv6 address.
-\item IPv6 address that is contained in the Routing-Header-Type-2 from the associated extension header. If the extension header is not present, use the Destination IPv6 address.
-\end{itemize}
-\item Else skip IPv6 extension headers and calculate the hash as
-defined for an IPv6 packet without extension headers (see \ref{itm:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS hash types/hash on IPv6 packets without extension headers}).
-\end{itemize}
-
\drivernormative{\subparagraph}{Setting RSS parameters}{Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) }
A driver MUST NOT send the VIRTIO_NET_CTRL_MQ_RSS_CONFIG command if the feature VIRTIO_NET_F_RSS has not been negotiated.
@@ -4057,12 +4126,12 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
A driver MUST use \field{indirection_table_mask} values that are less than \field{rss_max_indirection_table_length} reported by a device.
-A driver MUST NOT set any VIRTIO_NET_RSS_HASH_TYPE_ flags that are not supported by a device.
+A driver MUST NOT set any VIRTIO_NET_HASH_TYPE_ flags that are not supported by a device.
\devicenormative{\subparagraph}{RSS processing}{Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS processing}
The device MUST determine the destination queue for a network packet as follows:
\begin{itemize}
-\item Calculate the hash of the packet as defined in \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS hash types}
+\item Calculate the hash of the packet as defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets}.
\item If the device did not calculate the hash for the specific packet, the device directs the packet to the receiveq specified by \field{unclassified_queue} of virtio_net_rss_config structure (value of 0 corresponds to receiveq1).
\item Apply \field{indirection_table_mask} to the calculated hash and use the result as the index in the indirection table to get 0-based number of destination receiveq (value of 0 corresponds to receiveq1).
\end{itemize}
--
2.17.1
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