The reason of "ping: sendto: No buffer space available" and link_irq variable

[Tugrul Erdogan]

Hi,

I am using FreeBSD alpha2 amd64 on my router and after packet loaded test
attack I am taking
"ping: sendto: No buffer space available" error when running ping from
router to victim directoion. The nic is "Intel 82599EB". Whenever this
problem began to show, I can track the packages by tcpdump but I think the
packages can not be created physically when they are reached physical
layer. Doing the nic down/up can not be solved the problem.

When I testing I have found the "dev.ix.0.link_irq" value is increased very
differently from other nic's link_irq values. So after assigning the value
of 2 to this link_irq variable the problem solved.

I want to your help at two path; firstly why should I take this error.
Secondly what is the role of the link_irq variable, what is the situations
which are trigger to increase the link_irq variable and is the real reason
of this problem the link_irq variable or anything else under this
mechanism?

Thanks and best regards,