x/net/ipv4: TestPacketConnReadWriteUnicastICMP failures with `destination unreachable`

[gopherbot]

#!watchflakes
post <- pkg == "golang.org/x/net/ipv4" && test == "TestPacketConnReadWriteUnicastICMP" && `got type=destination unreachable`

Issue created automatically to collect these failures.

Example (log):

--- FAIL: TestPacketConnReadWriteUnicastICMP (0.01s)
    unicast_test.go:175: got type=destination unreachable, code=3; want type=echo reply, code=0

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

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

2023-01-05 16:42 netbsd-amd64-9_3 net@f8411da7 go@145dd384 x/net/ipv4.TestPacketConnReadWriteUnicastICMP (log)

--- FAIL: TestPacketConnReadWriteUnicastICMP (0.01s)
    unicast_test.go:175: got type=destination unreachable, code=3; want type=echo reply, code=0

— watchflakes

[bcmills]

See also #57842.