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Laurence Evans authored
There is a long-standing problem with the packet-timestamp matching in the driver. When a PTP packet is received by the MC, the FPGA timestamps the packet and the MC sends the timestamp and 6 bytes of the UUID to the driver. The driver then matches the timestamp against received packets using the same 6 bytes of UUID. The problem comes from the choice of which 6 bytes to use. The PTP spec is slightly contradictory and misleading in one of the two places where the UUIDs are discussed. From section 7.2.2.2 of the spec, a PTPD2 UUID can be either a EUI-64 or a EUI-64 constructed from a EUI-48. The typical ethernet based implementation uses a EUI-64 constructed from a EUI-48. This works by taking the first 3 bytes of the MAC address of the NIC being used for PTP (the OUI), then inserting 0xFF, 0xFE, then taking the last 3 bytes of the MAC address giving MAC[0], MAC[1], MAC[2], 0xFF, 0xFE, MAC[3], MAC[4], MAC[5] The current MC firmware and driver discard the first two bytes of this UUID and packets are matched against timestamps using bytes 2 to 7 so there is a small risk that in a deployment of Solarflare PTP NICs used with other vendors NICs, that a PTP packet could be matched against the wrong timestamp. This applies to all other organisations whose third byte of the OUI is 0x53. It's a long list but I notice that it includes Cisco. The necessary modifications to use bytes 0-2 and 5-7 of the UUID to match against are quite small but introduce incompatibility between older version of the firmware and driver. When PTP is enabled via SO_TIMESTAMPING specifying PTP V2, the driver will try to enable PTP in the firmware using the enhanced mode (above). If the firmware returns an error, the driver will enable PTP in the firmware using the old mode. [bwh: Fix some style errors; remove private ioctl bits] Signed-off-by:
Ben Hutchings <bhutchings@solarflare.com>
c939a316