1 files changed, 231 insertions, 0 deletions
diff --git a/src/net/dnsclient.go b/src/net/dnsclient.go
new file mode 100644
index 0000000..e9c7384
--- /dev/null
+++ b/src/net/dnsclient.go
@@ -0,0 +1,231 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"sort"
+
+	"golang.org/x/net/dns/dnsmessage"
+)
+
+// provided by runtime
+func fastrand() uint32
+
+func randInt() int {
+	x, y := fastrand(), fastrand()    // 32-bit halves
+	u := uint(x)<<31 ^ uint(int32(y)) // full uint, even on 64-bit systems; avoid 32-bit shift on 32-bit systems
+	i := int(u >> 1)                  // clear sign bit, even on 32-bit systems
+	return i
+}
+
+func randIntn(n int) int {
+	return randInt() % n
+}
+
+// reverseaddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP
+// address addr suitable for rDNS (PTR) record lookup or an error if it fails
+// to parse the IP address.
+func reverseaddr(addr string) (arpa string, err error) {
+	ip := ParseIP(addr)
+	if ip == nil {
+		return "", &DNSError{Err: "unrecognized address", Name: addr}
+	}
+	if ip.To4() != nil {
+		return uitoa(uint(ip[15])) + "." + uitoa(uint(ip[14])) + "." + uitoa(uint(ip[13])) + "." + uitoa(uint(ip[12])) + ".in-addr.arpa.", nil
+	}
+	// Must be IPv6
+	buf := make([]byte, 0, len(ip)*4+len("ip6.arpa."))
+	// Add it, in reverse, to the buffer
+	for i := len(ip) - 1; i >= 0; i-- {
+		v := ip[i]
+		buf = append(buf, hexDigit[v&0xF],
+			'.',
+			hexDigit[v>>4],
+			'.')
+	}
+	// Append "ip6.arpa." and return (buf already has the final .)
+	buf = append(buf, "ip6.arpa."...)
+	return string(buf), nil
+}
+
+func equalASCIIName(x, y dnsmessage.Name) bool {
+	if x.Length != y.Length {
+		return false
+	}
+	for i := 0; i < int(x.Length); i++ {
+		a := x.Data[i]
+		b := y.Data[i]
+		if 'A' <= a && a <= 'Z' {
+			a += 0x20
+		}
+		if 'A' <= b && b <= 'Z' {
+			b += 0x20
+		}
+		if a != b {
+			return false
+		}
+	}
+	return true
+}
+
+// isDomainName checks if a string is a presentation-format domain name
+// (currently restricted to hostname-compatible "preferred name" LDH labels and
+// SRV-like "underscore labels"; see golang.org/issue/12421).
+func isDomainName(s string) bool {
+	// See RFC 1035, RFC 3696.
+	// Presentation format has dots before every label except the first, and the
+	// terminal empty label is optional here because we assume fully-qualified
+	// (absolute) input. We must therefore reserve space for the first and last
+	// labels' length octets in wire format, where they are necessary and the
+	// maximum total length is 255.
+	// So our _effective_ maximum is 253, but 254 is not rejected if the last
+	// character is a dot.
+	l := len(s)
+	if l == 0 || l > 254 || l == 254 && s[l-1] != '.' {
+		return false
+	}
+
+	last := byte('.')
+	nonNumeric := false // true once we've seen a letter or hyphen
+	partlen := 0
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		switch {
+		default:
+			return false
+		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '_':
+			nonNumeric = true
+			partlen++
+		case '0' <= c && c <= '9':
+			// fine
+			partlen++
+		case c == '-':
+			// Byte before dash cannot be dot.
+			if last == '.' {
+				return false
+			}
+			partlen++
+			nonNumeric = true
+		case c == '.':
+			// Byte before dot cannot be dot, dash.
+			if last == '.' || last == '-' {
+				return false
+			}
+			if partlen > 63 || partlen == 0 {
+				return false
+			}
+			partlen = 0
+		}
+		last = c
+	}
+	if last == '-' || partlen > 63 {
+		return false
+	}
+
+	return nonNumeric
+}
+
+// absDomainName returns an absolute domain name which ends with a
+// trailing dot to match pure Go reverse resolver and all other lookup
+// routines.
+// See golang.org/issue/12189.
+// But we don't want to add dots for local names from /etc/hosts.
+// It's hard to tell so we settle on the heuristic that names without dots
+// (like "localhost" or "myhost") do not get trailing dots, but any other
+// names do.
+func absDomainName(b []byte) string {
+	hasDots := false
+	for _, x := range b {
+		if x == '.' {
+			hasDots = true
+			break
+		}
+	}
+	if hasDots && b[len(b)-1] != '.' {
+		b = append(b, '.')
+	}
+	return string(b)
+}
+
+// An SRV represents a single DNS SRV record.
+type SRV struct {
+	Target   string
+	Port     uint16
+	Priority uint16
+	Weight   uint16
+}
+
+// byPriorityWeight sorts SRV records by ascending priority and weight.
+type byPriorityWeight []*SRV
+
+func (s byPriorityWeight) Len() int { return len(s) }
+func (s byPriorityWeight) Less(i, j int) bool {
+	return s[i].Priority < s[j].Priority || (s[i].Priority == s[j].Priority && s[i].Weight < s[j].Weight)
+}
+func (s byPriorityWeight) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+// shuffleByWeight shuffles SRV records by weight using the algorithm
+// described in RFC 2782.
+func (addrs byPriorityWeight) shuffleByWeight() {
+	sum := 0
+	for _, addr := range addrs {
+		sum += int(addr.Weight)
+	}
+	for sum > 0 && len(addrs) > 1 {
+		s := 0
+		n := randIntn(sum)
+		for i := range addrs {
+			s += int(addrs[i].Weight)
+			if s > n {
+				if i > 0 {
+					addrs[0], addrs[i] = addrs[i], addrs[0]
+				}
+				break
+			}
+		}
+		sum -= int(addrs[0].Weight)
+		addrs = addrs[1:]
+	}
+}
+
+// sort reorders SRV records as specified in RFC 2782.
+func (addrs byPriorityWeight) sort() {
+	sort.Sort(addrs)
+	i := 0
+	for j := 1; j < len(addrs); j++ {
+		if addrs[i].Priority != addrs[j].Priority {
+			addrs[i:j].shuffleByWeight()
+			i = j
+		}
+	}
+	addrs[i:].shuffleByWeight()
+}
+
+// An MX represents a single DNS MX record.
+type MX struct {
+	Host string
+	Pref uint16
+}
+
+// byPref implements sort.Interface to sort MX records by preference
+type byPref []*MX
+
+func (s byPref) Len() int           { return len(s) }
+func (s byPref) Less(i, j int) bool { return s[i].Pref < s[j].Pref }
+func (s byPref) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+// sort reorders MX records as specified in RFC 5321.
+func (s byPref) sort() {
+	for i := range s {
+		j := randIntn(i + 1)
+		s[i], s[j] = s[j], s[i]
+	}
+	sort.Sort(s)
+}
+
+// An NS represents a single DNS NS record.
+type NS struct {
+	Host string
+}