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Subject: [PATCH v5 1/1] 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 | 348 ++++++++++++++++++++++++++++++++++------------------ 1 file changed, 230 insertions(+), 118 deletions(-) diff --git a/content.tex b/content.tex index b91a132..45ad5e9 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(57)] 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. @@ -2995,35 +2998,17 @@ \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. +The following field, \field{rss_max_key_size} only exist if VIRTIO_NET_F_RSS or VIRTIO_NET_F_HASH_REPORT is set. +It specifies the maximal supported length of RSS key in bytes. -Field \field{rss_max_key_size} specifies the maximal supported length of RSS key in bytes. +The following field, \field{rss_max_indirection_table_length} only exist if VIRTIO_NET_F_RSS is set. +It specifies the maximal number of 16-bit entries in RSS indirection table. -Field \field{rss_max_indirection_table_length} specifies the maximal number of 16-bit entries in RSS indirection table. +The next field, \field{supported_hash_types} exists only if the device supports hash calculation, +i.e. if VIRTIO_NET_F_RSS or VIRTIO_NET_F_HASH_REPORT is set. -Field \field{supported_hash_types} contains the bitmask of supported RSS hash types. - -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} @@ -3048,7 +3033,7 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device negotiated. The device MUST set \field{rss_max_key_size} to at least 40, if it offers -VIRTIO_NET_F_RSS. +VIRTIO_NET_F_RSS or VIRTIO_NET_F_HASH_REPORT. The device MUST set \field{rss_max_indirection_table_length} to at least 128, if it offers VIRTIO_NET_F_RSS. @@ -3195,6 +3180,9 @@ \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_report; (Only if VIRTIO_NET_F_HASH_REPORT negotiated) + le16 padding_reserved; (Only if VIRTIO_NET_F_HASH_REPORT negotiated) }; \end{lstlisting} @@ -3517,6 +3505,12 @@ \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 @@ -3619,6 +3613,181 @@ \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 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. +\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 a key as defined in \field{hash_key_data} and \field{hash_key_length} of the virtio_net_rss_config structure (see +\ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / Setting RSS parameters}). +\end{itemize} + +If the feature VIRTIO_NET_F_RSS was not negotiated: +\begin{itemize} +\item The device uses \field{hash_types} of the virtio_net_hash_config structure as 'Enabled hash types' bitmask. +\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 +\ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode / Hash calculation}). +\end{itemize} + +Note that if the device offers VIRTIO_NET_F_HASH_REPORT, even if it supports only one pair of virtqueues, it MUST support +at least one of commands of VIRTIO_NET_CTRL_MQ class to configure reported hash parameters: +\begin{itemize} +\item If the device offers VIRTIO_NET_F_RSS, it MUST support VIRTIO_NET_CTRL_MQ_RSS_CONFIG command per + \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / Setting RSS parameters}. +\item Otherwise the device MUST support VIRTIO_NET_CTRL_MQ_HASH_CONFIG command per + \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode / Hash calculation}. +\end{itemize} + +\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 according 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 '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} + +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. + +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. + +Possible values that the device can report in \field{hash_report} 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 @@ -3896,6 +4065,7 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi #define VIRTIO_NET_CTRL_MQ 4 #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET 0 (for automatic receive steering) #define VIRTIO_NET_CTRL_MQ_RSS_CONFIG 1 (for configurable receive steering) + #define VIRTIO_NET_CTRL_MQ_HASH_CONFIG 2 (for configurable hash calculation) \end{lstlisting} If more than one multiqueue mode is negotiated, the resulting device configuration is defined by the last command sent by the driver. @@ -3961,10 +4131,37 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi according to the native endian of the guest rather than (necessarily when not using the legacy interface) little-endian. +\subparagraph{Hash calculation}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode / Hash calculation} +If VIRTIO_NET_F_HASH_REPORT was negotiated and the device uses automatic receive steering, +the device MUST support a command to configure hash calculation parameters. + +The driver provides parameters for hash calculation as follows: + +\field{class} VIRTIO_NET_CTRL_MQ, \field{command} VIRTIO_NET_CTRL_MQ_HASH_CONFIG. + +The \field{command-specific-data} has following format: +\begin{lstlisting} +struct virtio_net_hash_config { + le32 hash_types; + le16 reserved[4]; + u8 hash_key_length; + u8 hash_key_data[hash_key_length]; +}; +\end{lstlisting} +Field \field{hash_types} contains a bitmask of allowed hash types as +defined in +\ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets / Supported/enabled hash types}. +Initially the device has all hash types disabled and reports only VIRTIO_NET_HASH_REPORT_NONE. + +Field \field{reserved} MUST contain zeroes. It is defined to make the structure to match the layout of virtio_net_rss_config structure, +defined in \ref{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS)}. + +Fields \field{hash_key_length} and \field{hash_key_data} define the key to be used in hash calculation. + \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} @@ -3981,7 +4178,8 @@ \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 @@ -3995,93 +4193,7 @@ \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} +Fields \field{hash_key_length} and \field{hash_key_data} define the key to be used in hash calculation. \drivernormative{\subparagraph}{Setting RSS parameters}{Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) } @@ -4093,12 +4205,12 @@ \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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