x/net/ipv4: TestRawConnReadWriteUnicastICMP failures with `i/o timeout`

[gopherbot]

#!watchflakes
post <- pkg == "golang.org/x/net/ipv4" && test == "TestRawConnReadWriteUnicastICMP" && `i/o timeout`

Issue created automatically to collect these failures.

Example (log):

--- FAIL: TestRawConnReadWriteUnicastICMP (0.11s)
    unicast_test.go:249: read ip 0.0.0.0: raw-read ip4 0.0.0.0: i/o timeout

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
post <- pkg == "golang.org/x/net/ipv4" && test == "TestRawConnReadWriteUnicastICMP"

2023-03-09 22:21 netbsd-arm-bsiegert net@9f24bb44 go@4df95d51 x/net/ipv4.TestRawConnReadWriteUnicastICMP (log)

--- FAIL: TestRawConnReadWriteUnicastICMP (0.11s)
    unicast_test.go:249: read ip 0.0.0.0: raw-read ip4 0.0.0.0: i/o timeout

— watchflakes

[bcmills]

Arbitrary timeouts were added to that test (and many others) in https://go.dev/cl/21360043; it isn't at all clear to me why they were added, since the test fails if the timeout expires anyway.

Probably the deadlines just need to be removed (from all of those tests).

(https://cs.opensource.google/go/x/net/+/master:ipv4/unicast_test.go;l=237-247;drc=c7608f3a8462fd23f95e21be49b40c7b9c20c74a)

(CC @ianlancetaylor)

[gopherbot]

Change https://go.dev/cl/492620 mentions this issue: ipv4,ipv6: remove unneeded deadlines added for flaky tests