net: getting setsockopt: invalid argument when setting TCP keep-alive on Solaris

[panjf2000]

During my work on CL 542275, I discovered a uncanny failure on Solaris: the existing code of setting the TCP keep-alive via SetsockoptInt(syscall.IPPROTO_TCP, syscall.TCP_KEEPALIVE_THRESHOLD, msecs) always failed with setsockopt: invalid argument, resulting in failures from newly added tests:

--- FAIL: TestTCPConnDialerKeepAliveConfig (0.00s)
    tcpconn_keepalive_solaris_test.go:87: TCP_KEEPIDLE: got 7200000ms; want 2s
--- FAIL: TestTCPConnListenerKeepAliveConfig (0.00s)
    tcpconn_keepalive_solaris_test.go:87: TCP_KEEPIDLE: got 7200000ms; want 2s
--- FAIL: TestTCPConnSetKeepAliveConfig (0.00s)
    tcpconn_keepalive_test.go:167: set tcp 127.0.0.1:33957->127.0.0.1:49663: setsockopt: invalid argument

Judging from the failure outputs, I suspect that the existing code of setting keep-alive parameters on solaris had been failing before CL 542275 which only splits the original function setKeepAlivePeriod on solaris and doesn't change how the code used to work, I think there was something wrong with the SetsockoptInt(syscall.IPPROTO_TCP, syscall.TCP_KEEPALIVE_THRESHOLD, msecs) system call on solaris, we just didn't notice this failure because that portion of the code has never been tested.

Filing this bug report for not blocking CL 542275 from an existing bug.

[panjf2000]

cc @neild @bcmills

[bcmills]

(attn @golang/solaris)

@panjf2000, does it also fail on the illumos builders?

[panjf2000]

I haven't verified it yet, shooting a trybot with TRY=illumos didn't seem to work?
@bcmills

[panjf2000]

Related issue #62254

[panjf2000]

It seemed that it won't fail on illumos according to this.
@bcmills

[gopherbot]

Change https://go.dev/cl/577195 mentions this issue: net: implement TCP_KEEPIDLE, TCP_KEEPINTVL, and TCP_KEEPCNT on Solaris 11.4