Intel i210 and i226 does this. But the i226 has a few variants.
Yes. I'm aware. Perhaps I'm more stupid about this topic than normal, but it looks to me like the NICs I have do (NIC names have been changed for clarity, but all other output is untouched):
$ ethtool -T intel-nic
Time stamping parameters for intel-nic:
Capabilities:
hardware-transmit
software-transmit
hardware-receive
software-receive
software-system-clock
hardware-raw-clock
Hardware timestamp provider index: 0
Hardware timestamp provider qualifier: Precise (IEEE 1588 quality)
Hardware timestamp source: MAC
Hardware Transmit Timestamp Modes:
off
on
Hardware Receive Filter Modes:
none
all
$ ethtool -T brcm-nic
Time stamping parameters for brcm-nic:
Capabilities:
hardware-transmit
software-transmit
hardware-receive
software-receive
software-system-clock
hardware-raw-clock
Hardware timestamp provider index: 0
Hardware timestamp provider qualifier: Precise (IEEE 1588 quality)
Hardware timestamp source: MAC
Hardware Transmit Timestamp Modes:
off
on
Hardware Receive Filter Modes:
none
ptpv1-l4-event
ptpv2-l4-event
ptpv2-l2-event~~yaaaaay~~
Also, who the heck knows if my switches are behaving correctly? I may be dealing with a system with multiple failing components.
I'd never considered Mellanox hardware... I'd always thought of them as "super expensive datacenter hardware", but non-Infiniband cards I can see on Newegg aren't entirely-unreasonably priced. (TBD if I can find a PCI-E 2.0 1x card, though). I'd not heard of ASIX, and they have a card that would fit in my slot, but -sadly- no in-tree driver. It looks like the only in-tree driver is for a 100mbit card... the AX88796C.
Anyway, thanks for the advice/info and the mention of more-reliable manufacturers.