82598EB Datasheet, PDF (228/596 Pages) Intel Corporation – Intel® 82598EB 10 Gigabit Ethernet Controller Datasheet

Intel^® 82598EB 10 GbE Controller - Receive Functionality
The IP and TCP checksum error bits are valid only when the IPv4 or TCP/UDP checksum(s) is performed
on the received packet as indicated via IPCS and L4CS. These, along with the other error bits are valid
only when the EOP and DD bits are set in the descriptor.
Note: Receive checksum errors have no effect on packet filtering.
CE
Indicates an Ethernet CRC error was detected. This bit is valid only when the EOP and DD bits are set
and are not set in descriptors unless FCTRL.SBP (store-bad-packets) is set.
LE
Indicates an Ethernet L2 length error was detected. This bit is valid only when the EOP and DD bits are
set and are not set in descriptors unless FCTRL.SBP (store-bad-packets) is set.
HBO (Header Buffer Overflow)
1. In Header split mode, when SRRCTL BSIZEHEADER is smaller than HDR_BUF_LEN, then HBO is set
to 1b. In this case, the header is not split. Instead, the header resides within the host packet buffer.
If SPH is set, then the HDR_BUF_LEN field is still valid and equal to the calculated size of the
header. However, the header is not copied into the header buffer.
2. HBO should be ignored each time SPH is not set to 1b.
Note: Most error information appears only when the SBP bit (FCTRL.SBP) is set and a bad packet is
received.
PKT_Buf_Length (16)
Number of bytes exists in the host packet buffer.
The length covers the data written to a receive buffer including CRC bytes (if any). Software must read
multiple descriptors to determine the complete length for packets that span multiple receive buffers. If
SRRCTL.DESC_TYPE = 4 (advanced descriptor header replication large packet only) and the total
packet length is smaller than the size of the header buffer (no replication is done), this field still reflects
the size of the packet, although no data is written to the data buffer. If SRRCTL.DESC_TYPE = 2
(advanced descriptor header splitting) and the buffer is not split because the header is bigger than the
allocated header buffer, this field reflects the size of the data written to the data buffer (header + data).
VLAN Tag (16)
Hardware stores additional information in the receive descriptor for 802.1q packets. If the packet type
is 802.1q (determined when a packet matches VET and VLNCTRL.VME=1b), then the VLAN Tag field
records the VLAN information and the four-byte VLAN information is stripped from the packet data
storage. Otherwise, the VLAN Tag field contains 0x0000.
Table 3-56. VLAN Tag Field Layout (for 802.1q Packet)
15 13
12
Priority
CFI
11
0
VLAN
Priority and CFI are part of 803.1q specifications.
228