net: setKeepAlivePeriod may be wrong on Solaris

[ianlancetaylor]

In revision f956740 the function setKeepAlivePeriod in the net package was changed on Solaris to use TCP_KEEPIDLE and TCP_KEEPINTVL. However, I am told that on Solaris 11.2, those symbols are not defined. They are defined in our syscall package because they are defined on Illumos, which is derived from OpenSolaris. If we want Go to have support for Solaris proper, not just OpenSolaris, we should probably go back to the earlier Solaris-specific version of setKeepAlivePeriod.


[4ad]

The problem here is that it impossible to perfectly emulate TCP_KEEPINTVL + TCP_KEEPIDLE using TCP_KEEPALIVE_THRESHOLD and TCP_KEEPALIVE_ABORT_THRESHOLD.

Generally speaking, TCP_KEEPALIVE_ABORT_THRESHOLD = TCP_KEEPCNT * TCP_KEEPINTVL, however, when using TCP_KEEPALIVE_ABORT_THRESHOLD, Solaris will not send probes at equal intervals, but will use an exponential backoff algorithm. That is not what we want.

If it's "good enough", and we decide to go with it, we need to find a good value for TCP_KEEPCNT. I don't know what a good value is.

[4ad]

Mikio, do you know what a good TCP_KEEPCNT value is?

[mikioh]

Maybe 2^3? Agree that TCP_KEEPALIVE_THRESHOLD is equivalent to TCP_KEEPIDLE, TCP_KEEPALIVE_ABORT_THRESHOLD is equivalent to TCP_KEEPINTVL x TCP_KEEPCNT.

[gopherbot]

CL https://golang.org/cl/7690 mentions this issue.