[netperf-talk] setting SO_DONTROUTE for UDP tests by default?

[Andrew Gallatin]

Rick Jones wrote:

> also connected to their employer's site lans.  Some of their tests include 
> triggering link-down events on their NICs under test.  This can then cause the 
> IP stack on the test system to seek another path, and that can be the default 
> route leading out onto the site network.  If the netperf test happens to be 
> UDP_STREAM things can get rather ugly from that point on...

You're describing the Solaris NICDRV certification test, eh?

> Clearly these folks are being, well frankly they are being idiots running 
> network tests on systems without an "air gap" between them and the rest of the 

It is hard to implement an air gap when your test hardware is 2500 miles
from you, and your only access is remote.  Serial console access gets
old after a while..

> world.  And while I don't normally like to cover the backsides of idiots I am 
> getting a little soft in my middle years and was thinking...
> 
> Would it inconvenience folks very much if for UDP tests, by default netperf were 
> to set SO_DONTROUTE on the data socket, and only not set it by explicit 
> command-line action on the part of the user?

Can you optionally set SO_DONTROUTE even for TCP tests?  I had
an issue (with NICDRV) where the test suite would bounce our
interface up & down while running netperf TCP_STREAM.  The problem
was that the DUT (myri10ge) implemented LSO, and the Solaris driver
for the on-board interface holding the default route did not.  When our
NIC was taken down, the kernel re-sent some 60BK "packets" to
a driver that was utterly unprepared to handle anything larger
than 1518 bytes.  It scribbled over random kernel memory when
copying the 60KB packet to a 1518 byte buffer, and things
went boom in strange an unpredictable ways.  It took me
over a day to figure out what was happening..  The "fix" was
to delete the default route before running those tests..

Drew