1 files changed, 421 insertions, 0 deletions
diff --git a/src/pkg/net/ip.go b/src/pkg/net/ip.go
new file mode 100644
index 000000000..774f048ca
--- /dev/null
+++ b/src/pkg/net/ip.go
@@ -0,0 +1,421 @@
+// 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.
+
+// IP address manipulations
+//
+// IPv4 addresses are 4 bytes; IPv6 addresses are 16 bytes.
+// An IPv4 address can be converted to an IPv6 address by
+// adding a canonical prefix (10 zeros, 2 0xFFs).
+// This library accepts either size of byte array but always
+// returns 16-byte addresses.
+
+package net
+
+import (
+	"net"
+)
+
+// IP address lengths (bytes).
+const (
+	IPv4len = 4;
+	IPv6len = 16
+)
+
+// An IP is a single IP address, an array of bytes.
+// Functions in this package accept either 4-byte (IP v4)
+// or 16-byte (IP v6) arrays as input.  Unless otherwise
+// specified, functions in this package always return
+// IP addresses in 16-byte form using the canonical
+// embedding.
+//
+// Note that in this documentation, referring to an
+// IP address as an IPv4 address or an IPv6 address
+// is a semantic property of the address, not just the
+// length of the byte array: a 16-byte array can still
+// be an IPv4 address.
+type IP []byte;
+
+// An IP mask is an IP address.
+type IPMask []byte;
+
+// IPv4 returns the IP address (in 16-byte form) of the
+// IPv4 address a.b.c.d.
+func IPv4(a, b, c, d byte) IP {
+	p := make(IP, IPv6len);
+	for i := 0; i < 10; i++ {
+		p[i] = 0
+	}
+	p[10] = 0xff;
+	p[11] = 0xff;
+	p[12] = a;
+	p[13] = b;
+	p[14] = c;
+	p[15] = d;
+	return p
+}
+
+// Well-known IPv4 addresses
+var (
+	IPv4bcast = IPv4(255, 255, 255, 255);	// broadcast
+	IPv4allsys = IPv4(224, 0, 0, 1);	// all systems
+	IPv4allrouter = IPv4(224, 0, 0, 2);	// all routers
+	IPv4zero = IPv4(0, 0, 0, 0);	// all zeros
+)
+
+// Well-known IPv6 addresses
+var (
+	IPzero = make(IP, IPv6len);	// all zeros
+)
+
+// Is p all zeros?
+func isZeros(p IP) bool {
+	for i := 0; i < len(p); i++ {
+		if p[i] != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+// To4 converts the IPv4 address ip to a 4-byte representation.
+// If ip is not an IPv4 address, To4 returns nil.
+func (ip IP) To4() IP {
+	if len(ip) == IPv4len {
+		return ip
+	}
+	if len(ip) == IPv6len
+	&& isZeros(ip[0:10])
+	&& ip[10] == 0xff
+	&& ip[11] == 0xff {
+		return ip[12:16]
+	}
+	return nil
+}
+
+// To16 converts the IP address ip to a 16-byte representation.
+// If ip is not an IP address (it is the wrong length), To16 returns nil.
+func (ip IP) To16() IP {
+	if len(ip) == IPv4len {
+		return IPv4(ip[0], ip[1], ip[2], ip[3])
+	}
+	if len(ip) == IPv6len {
+		return ip
+	}
+	return nil
+}
+
+// Default route masks for IPv4.
+var (
+	classAMask = IPMask(IPv4(0xff, 0, 0, 0));
+	classBMask = IPMask(IPv4(0xff, 0xff, 0, 0));
+	classCMask = IPMask(IPv4(0xff, 0xff, 0xff, 0));
+)
+
+// DefaultMask returns the default IP mask for the IP address ip.
+// Only IPv4 addresses have default masks; DefaultMask returns
+// nil if ip is not a valid IPv4 address.
+func (ip IP) DefaultMask() IPMask  {
+	if ip = ip.To4(); ip == nil {
+		return nil
+	}
+	switch true {
+	case ip[0] < 0x80:
+		return classAMask;
+	case ip[0] < 0xC0:
+		return classBMask;
+	default:
+		return classCMask;
+	}
+	return nil;	// not reached
+}
+
+// Mask returns the result of masking the IP address ip with mask.
+func (ip IP) Mask(mask IPMask) IP {
+	n := len(ip);
+	if n != len(mask) {
+		return nil
+	}
+	out := make(IP, n);
+	for i := 0; i < n; i++ {
+		out[i] = ip[i] & mask[i];
+	}
+	return out
+}
+
+// Convert i to decimal string.
+func itod(i uint) string {
+	if i == 0 {
+		return "0"
+	}
+
+	// Assemble decimal in reverse order.
+	var b [32]byte;
+	bp := len(b);
+	for ; i > 0; i /= 10 {
+		bp--;
+		b[bp] = byte(i%10) + '0'
+	}
+
+	return string(b[bp:len(b)])
+}
+
+// Convert i to hexadecimal string.
+func itox(i uint) string {
+	if i == 0 {
+		return "0"
+	}
+
+	// Assemble hexadecimal in reverse order.
+	var b [32]byte;
+	bp := len(b);
+	for ; i > 0; i /= 16 {
+		bp--;
+		b[bp] = "0123456789abcdef"[byte(i%16)]
+	}
+
+	return string(b[bp:len(b)])
+}
+
+// String returns the string form of the IP address ip.
+// If the address is an IPv4 address, the string representation
+// is dotted decimal ("74.125.19.99").  Otherwise the representation
+// is IPv6 ("2001:4860:0:2001::68").
+func (ip IP) String() string {
+	p := ip;
+
+	// If IPv4, use dotted notation.
+	if p4 := p.To4(); len(p4) == 4 {
+		return itod(uint(p4[0]))+"."
+			+itod(uint(p4[1]))+"."
+			+itod(uint(p4[2]))+"."
+			+itod(uint(p4[3]))
+	}
+	if len(p) != IPv6len {
+		return "?"
+	}
+
+	// Find longest run of zeros.
+	e0 := -1;
+	e1 := -1;
+	for i := 0; i < 16; i+=2 {
+		j := i;
+		for j < 16 && p[j] == 0 && p[j+1] == 0 {
+			j += 2
+		}
+		if j > i && j - i > e1 - e0 {
+			e0 = i;
+			e1 = j
+		}
+	}
+
+	// Print with possible :: in place of run of zeros
+	var s string;
+	for i := 0; i < 16; i += 2 {
+		if i == e0 {
+			s += "::";
+			i = e1;
+			if i >= 16 {
+				break
+			}
+		} else if i > 0 {
+			s += ":"
+		}
+		s += itox((uint(p[i])<<8) | uint(p[i+1]))
+	}
+	return s
+}
+
+// If mask is a sequence of 1 bits followed by 0 bits,
+// return the number of 1 bits.
+func simpleMaskLength(mask IPMask) int {
+	var i int;
+	for i = 0; i < len(mask); i++ {
+		if mask[i] != 0xFF {
+			break
+		}
+	}
+	n := 8*i;
+	v := mask[i];
+	for v & 0x80 != 0 {
+		n++;
+		v <<= 1
+	}
+	if v != 0 {
+		return -1
+	}
+	for i++; i < len(mask); i++ {
+		if mask[i] != 0 {
+			return -1
+		}
+	}
+	return n
+}
+
+// String returns the string representation of mask.
+// If the mask is in the canonical form--ones followed by zeros--the
+// string representation is just the decimal number of ones.
+// If the mask is in a non-canonical form, it is formatted
+// as an IP address.
+func (mask IPMask) String() string {
+	switch len(mask) {
+	case 4:
+		n := simpleMaskLength(mask);
+		if n >= 0 {
+			return itod(uint(n+(IPv6len-IPv4len)*8))
+		}
+	case 16:
+		n := simpleMaskLength(mask);
+		if n >= 0 {
+			return itod(uint(n))
+		}
+	}
+	return IP(mask).String();
+}
+
+// Parse IPv4 address (d.d.d.d).
+func parseIPv4(s string) IP {
+	var p [IPv4len]byte;
+	i := 0;
+	for j := 0; j < IPv4len; j++ {
+		if j > 0 {
+			if s[i] != '.' {
+				return nil
+			}
+			i++;
+		}
+		var (
+			n int;
+			ok bool
+		)
+		n, i, ok = dtoi(s, i);
+		if !ok || n > 0xFF {
+			return nil
+		}
+		p[j] = byte(n)
+	}
+	if i != len(s) {
+		return nil
+	}
+	return IPv4(p[0], p[1], p[2], p[3])
+}
+
+// Parse IPv6 address.  Many forms.
+// The basic form is a sequence of eight colon-separated
+// 16-bit hex numbers separated by colons,
+// as in 0123:4567:89ab:cdef:0123:4567:89ab:cdef.
+// Two exceptions:
+//	* A run of zeros can be replaced with "::".
+//	* The last 32 bits can be in IPv4 form.
+// Thus, ::ffff:1.2.3.4 is the IPv4 address 1.2.3.4.
+func parseIPv6(s string) IP {
+	p := make(IP, 16);
+	ellipsis := -1;	// position of ellipsis in p
+	i := 0;	// index in string s
+
+	// Might have leading ellipsis
+	if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
+		ellipsis = 0;
+		i = 2;
+		// Might be only ellipsis
+		if i == len(s) {
+			return p
+		}
+	}
+
+	// Loop, parsing hex numbers followed by colon.
+	j := 0;
+L:	for j < IPv6len {
+		// Hex number.
+		n, i1, ok := xtoi(s, i);
+		if !ok || n > 0xFFFF {
+			return nil
+		}
+
+		// If followed by dot, might be in trailing IPv4.
+		if i1 < len(s) && s[i1] == '.' {
+			if ellipsis < 0 && j != IPv6len - IPv4len {
+				// Not the right place.
+				return nil
+			}
+			if j+IPv4len > IPv6len {
+				// Not enough room.
+				return nil
+			}
+			p4 := parseIPv4(s[i:len(s)]);
+			if p4 == nil {
+				return nil
+			}
+			// BUG: p[j:j+4] = p4
+			p[j] = p4[12];
+			p[j+1] = p4[13];
+			p[j+2] = p4[14];
+			p[j+3] = p4[15];
+			i = len(s);
+			j += 4;
+			break
+		}
+
+		// Save this 16-bit chunk.
+		p[j] = byte(n>>8);
+		p[j+1] = byte(n);
+		j += 2;
+
+		// Stop at end of string.
+		i = i1;
+		if i == len(s) {
+			break
+		}
+
+		// Otherwise must be followed by colon and more.
+		if s[i] != ':' && i+1 == len(s) {
+			return nil
+		}
+		i++;
+
+		// Look for ellipsis.
+		if s[i] == ':' {
+			if ellipsis >= 0 {	// already have one
+				return nil
+			}
+			ellipsis = j;
+			if i++; i == len(s) {	// can be at end
+				break
+			}
+		}
+	}
+
+	// Must have used entire string.
+	if i != len(s) {
+		return nil
+	}
+
+	// If didn't parse enough, expand ellipsis.
+	if j < IPv6len {
+		if ellipsis < 0 {
+			return nil
+		}
+		n := IPv6len - j;
+		for k := j-1; k >= ellipsis; k-- {
+			p[k+n] = p[k]
+		}
+		for k := ellipsis+n-1; k>=ellipsis; k-- {
+			p[k] = 0
+		}
+	}
+	return p
+}
+
+// ParseIP parses s as an IP address, returning the result.
+// The string s can be in dotted decimal ("74.125.19.99")
+// or IPv6 ("2001:4860:0:2001::68") form.
+// If s is not a valid textual representation of an IP address,
+// ParseIP returns nil.
+func ParseIP(s string) IP {
+	p := parseIPv4(s);
+	if p != nil {
+		return p
+	}
+	return parseIPv6(s)
+}
+