Data Sheet

Ethernet Controller I210 —Inline Functions
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2. If UdpIPv6Ex is enabled, try using UdpIPv6Ex function; else if UpdIPv6 is enabled try using UdpIPv6
function.
3. If IPv6Ex is enabled, try using the IPv6Ex function, else if IPv6 is enabled, try using the IPv6
function.
The following combinations are currently supported:
• Any combination of IPv4, TcpIPv4, and UdpIPv4.
•And/or.
• Any combination of either IPv6, TcpIPv6, and UdpIPv6 or IPv6Ex, TcpIPv6Ex, and UdpIPv6Ex.
When a packet cannot be parsed by the previously mentioned rules, it is assigned an RSS output index
= zero. The 32-bit tag (normally a result of the hash function) equals zero.
The 32-bit result of the hash computation is written into the packet descriptor and also provides an
index into the indirection table.
The following notation is used to describe the hash functions:
• Ordering is little endian in both bytes and bits. For example, the IP address 161.142.100.80
translates into 0xa18e6450 in the signature.
• A “^ “denotes bit-wise XOR operation of same-width vectors.
• @x-y denotes bytes x through y (including both of them) of the incoming packet, where byte 0 is
the first byte of the IP header. In other words, it is considered that all byte-offsets as offsets into a
packet where the framing layer header has been stripped out. Therefore, the source IPv4 address is
referred to as @12-15, while the destination v4 address is referred to as @16-19.
• @x-y, @v-w denotes concatenation of bytes x-y, followed by bytes v-w, preserving the order in
which they occurred in the packet.
All hash function variations (IPv4 and IPv6) follow the same general structure. Specific details for each
variation are described in the following section. The hash uses a random secret key length of 320 bits
(40 bytes); the key is typically supplied through the RSS Random Key Register (RSSRK).
The algorithm works by examining each bit of the hash input from left to right. Intel’s nomenclature
defines left and right for a byte-array as follows: Given an array K with k bytes, Intel’s nomenclature
assumes that the array is laid out as shown:
K[0] K[1] K[2] … K[k-1]
K[0] is the left-most byte, and the MSB of K[0] is the left-most bit. K[k-1] is the right-most byte, and
the LSB of K[k-1] is the right-most bit.
ComputeHash(input[], N)
For hash-input input[] of length N bytes (8N bits) and a random secret key K of 320 bits
Result = 0;
For each bit b in input[] {
if (b == 1) then Result ^= (left-most 32 bits of K);
shift K left 1 bit position;
}
return Result;
The following four pseudo-code examples are intended to help clarify exactly how the hash is to be
performed in four cases, IPv4 with and without ability to parse the TCP header and IPv6 with an without
a TCP header.