// IPv6 support too. So probe the kernel to figure it out.
func (p *ipStackCapabilities) probe() {
	switch runtime.GOOS {
	case "js", "wasip1":
		// Both ipv4 and ipv6 are faked; see net_fake.go.
		p.ipv4Enabled = true
		p.ipv6Enabled = true
		p.ipv4MappedIPv6Enabled = true
		return
	}

	s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
	switch err {