Intel PCI-X manual Packet Transmission, SNAP/VLAN Filter, 9.3 IPv4 Filter, 9.4 IPv6 Filter

Receive and Transmit Description

3.2.9.2SNAP/VLAN Filter

This filter checks the next headers looking for an IP header. It is capable of decoding Ethernet II, Ethernet SNAP, and IEEE 802.3ac headers. It skips past any of these intermediate headers and looks for the IP header. The receive configuration settings determine which next headers are accepted. See the various receive control configuration registers such as RCTL (RCTL.VFE), VET, and VFTA.

3.2.9.3IPv4 Filter

This filter checks for valid IPv4 headers. The version field is checked for a correct value (4). IPv4 headers are accepted if they are any size greater than or equal to 5 (dwords). If the IPv4 header is properly decoded, the IP checksum is checked for validity. The RXCSUM.IPOFL bit must be set for this filter to pass.

3.2.9.4IPv6 Filter

This filter checks for valid IPv6 headers, which are a fixed size and have no checksum. The IPv6 extension headers accepted are: Hop-by-Hop, Destination Options, and Routing. The maximum size next header accepted is 16 dwords (64 bytes).

All of the IPv6 extension headers supported by the Ethernet controller have the same header structure:

Byte 0 Byte 1 Byte 2 Byte 3

Next Header

Hdr Ext Len

•NEXT HEADER is a value that identifies the header type. The supported IPv6 next headers values are:

—Hop-by-Hop = 00h

—Destination Options = 3Ch

—Routing = 2Bh

•HDR EXT LEN is the 8 byte count of the header length, not including the first 8 bytes. For example, a value of 3 means that the total header size including the NEXT HEADER and HDR EXT LEN fields is 32 bytes (8 + 3*8).

—The RXCSUM.IPV6OFL bit must be set for this filter to pass.

3.2.9.5UDP/TCP Filter

This filter checks for a valid UDP or TCP header. The prototype next header values are 11h and 06h, respectively. The RXCSUM.TUOFL bit must be set for this filter to pass.

3.3Packet Transmission

The transmission process for regular (non-TCP Segmentation packets) involves:

•The protocol stack receives from an application a block of data that is to be transmitted.

34 Software Developer’s Manual