So the idea is for drivers to not tell the kernel that the interface
went down, while it's doing self-tests? I guess igb had this problem
fixed, according to the redhat bug, but I guess not e1000e.
Yes, I'm pretty sure the interface goes down during the offline portion
of the full set of self-tests, for my e1000e. Connected to my switch,
it takes longer than usual to autonegotiate a link. I should have
posted this in the initial report, but here's the actual output:
sudo ethtool -t eth0 offline
The test result is FAIL
The test extra info:
Register test (offline) 0
Eeprom test (offline) 0
Interrupt test (offline) 0
Loopback test (offline) 0
Link test (on/offline) 1
If this doesn't usually happen with e1000e, the long autonegotiation is
probably the corner case that's causing it. It's so long that the link
test fails. (also, would it make sense to do the link test first,
before offline tests that trigger autonegotiation? Or do we WANT to
flag problems like sketchy setups that require SmartSpeed fallback to
10baseT to make a working link?)
The other solution would be to save/restore routing table entries for that
interface. But that might cause problems in some corner cases. So it might be
a lot of work to implement safely, in the face of complex routing tables and/or
changes made during the self-test while the interface was still online. Oh
duh, nvm, there's more than just IPv4 to save/restore routing tables for. Some
custom protocol that ethtool doesn't know about would not have its routing
table saved/restored.
Anyway, thanks for having a look into this. It's not a problem for me
now that I know about it, just wanted to get it reported so at least the
docs could include a warning. That's all that I think really needs
doing, since checking every driver would be a lot of work.
how about:
ethtool(8):
...
offline
Perform all tests, including ones that interrupt normal
operation. Some drivers may bring the interface down/up during this process,
flushing routing table entries. They shouldn't, but be prepared just in case.
Report problems with specific drivers against the Linux kernel (not ethtool).
The "report a bug" sentence is probably too much, and could go.
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https://bugs.launchpad.net/bugs/1395269
Title:
[e1000e] ethtool -t eth0 offline loses routing table
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