func TestAppendPortIfNeeded(t *testing.T) {
	testCases := []struct {
		name   string
		addr   string
		port   int32
		expect string
	}{
		{
			name:   "IPv4 all-zeros bind address has port",
			addr:   "0.0.0.0:12345",
			port:   23456,
			expect: "0.0.0.0:12345",
		},
		{
			name:   "non-zeros IPv4 config",
			addr:   "9.8.7.6",
			port:   12345,
			expect: "9.8.7.6:12345",
		},
		{

        loadbalance
        kubernetes cluster.local in-addr.arpa ip6.arpa {
           pods insecure
           upstream
           fallthrough in-addr.arpa ip6.arpa
           ttl 30
        }
        health
    }
`,
			expectedCorefileData: `.:53 {
    errors
    health {
       lameduck 5s
    }
    ready
    kubernetes cluster.local in-addr.arpa ip6.arpa {
       pods insecure

	foundFree := func(addr offAddr, size uintptr) {
		if firstFree.base.lessEqual(addr) && addr.add(size-1).lessEqual(firstFree.bound) {
			// This range fits within the current firstFree window, so narrow
			// down the firstFree window to the base and bound of this range.
			firstFree.base = addr
			firstFree.bound = addr.add(size - 1)

		return secs[i].Addr < secs[j].Addr
	})

	// Check to make sure we don't have any overlaps.
	foundOverlap := false
	for i := 0; i < len(secs)-1; i++ {
		for j := i + 1; j < len(secs); j++ {
			s := secs[i]
			sn := secs[j]
			if secOverlaps(s, sn) {
				t.Errorf("unexpected: section %d:%q (addr=%x size=%x) overlaps section %d:%q (addr=%x size=%x)", i, s.Name, s.Addr, s.Size, i+1, sn.Name, sn.Addr, sn.Size)

// Find the elf.Section of a given shared library that contains a given address.
func findShlibSection(ctxt *Link, path string, addr uint64) *elf.Section {
	for _, shlib := range ctxt.Shlibs {
		if shlib.Path == path {
			for _, sect := range shlib.File.Sections[1:] { // skip the NULL section
				if sect.Addr <= addr && addr < sect.Addr+sect.Size {
					return sect
				}
			}
		}
	}
	return nil
}

// the elfMapping field is set. It populates the base and isData fields and
// returns an error.
func (f *file) computeBase(addr uint64) error {
	if f == nil || f.m == nil {
		return nil
	}
	if addr < f.m.start || addr >= f.m.limit {
		return fmt.Errorf("specified address %x is outside the mapping range [%x, %x] for file %q", addr, f.m.start, f.m.limit, f.name)
	}
	ef, err := elfOpen(f.name)
	if err != nil {

	}
	return proxyURL, nil
}

// useProxy reports whether requests to addr should use a proxy,
// according to the NO_PROXY or no_proxy environment variable.
// addr is always a canonicalAddr with a host and port.
func (cfg *config) useProxy(addr string) bool {
	if len(addr) == 0 {
		return true
	}
	host, port, err := net.SplitHostPort(addr)
	if err != nil {
		return false
	}
	if host == "localhost" {

			}
			t.Parallel()

			ln := newLocalListener(t, network)
			switch network {
			case "unix", "unixpacket":
				defer os.Remove(ln.Addr().String())
			}
			defer ln.Close()

			c, err := Dial(ln.Addr().Network(), ln.Addr().String())
			if err != nil {
				t.Fatal(err)
			}
			switch network {
			case "unix", "unixpacket":
				defer os.Remove(c.LocalAddr().String())
			}

	// expect host names, work with IP addresses.
	for _, tt := range parseIPTests {
		if tt.out != nil {
			addrs, err := LookupHost(tt.in)
			if len(addrs) != 1 || addrs[0] != tt.in || err != nil {
				t.Errorf("LookupHost(%q) = %v, %v, want %v, nil", tt.in, addrs, err, []string{tt.in})
			}
		} else if !testing.Short() {
			// We can't control what the host resolver does; if it can resolve, say,

		defer cancel()
	}

	rawConn, err := netDialer.DialContext(ctx, network, addr)
	if err != nil {
		return nil, err
	}

	colonPos := strings.LastIndex(addr, ":")
	if colonPos == -1 {
		colonPos = len(addr)
	}
	hostname := addr[:colonPos]

	if config == nil {
		config = defaultConfig()
	}
	// If no ServerName is set, infer the ServerName