Link cycling issue with some ix NICs
There's an issue with the XG-1540's 10 Gb NICs where they cycle link upon applying certain settings to the interface, like rxcsum and txcsum, among others. Some of those things are things we do in rc.linkup or things called from it. That leaves a variety of circumstances where the NIC gets stuck in a link down/up/down/up cycle. For instance if it loses link at any point past bootup, that happens. Among a variety of other reports:
It also has some general issue where any time the link comes up, it cycles on its own, "2 link states coalesced" is always logged.
After several hours into figuring out what all causes the thing to lose link, I came to the conclusion that it's way too many different things for us to avoid the root issue in the driver.
It doesn't happen on any Intel 10G cards with SFP+ that we have around. The XG-C2758 has no such problem.
The problem does not exist in the latest v3.1.14 driver from Intel.