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prefix.go
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// Copyright 2013 Mikio Hara. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE.
package ipaddr
import (
"encoding"
"encoding/binary"
"fmt"
"math"
"math/big"
"math/bits"
"net"
)
var (
_ encoding.BinaryMarshaler = &Prefix{}
_ encoding.BinaryUnmarshaler = &Prefix{}
_ encoding.TextMarshaler = &Prefix{}
_ encoding.TextUnmarshaler = &Prefix{}
_ fmt.Stringer = &Prefix{}
)
const (
IPv4PrefixLen = 8 * net.IPv4len // maximum number of prefix length in bits
IPv6PrefixLen = 8 * net.IPv6len // maximum number of prefix length in bits
)
// A Prefix represents an IP address prefix.
type Prefix struct {
net.IPNet
}
func (p *Prefix) lastIPv4Int() ipv4Int {
return ipToIPv4Int(p.IP) | ipv4Int(^mask32(p.Len()))
}
func (p *Prefix) lastIPv4MappedIPv6Int() ipv6Int {
i4 := ipToIPv4Int(p.IP) | ipv4Int(^mask32(p.Len()))
var i6 ipv6Int
i6[1] = 0x0000ffff00000000 | uint64(i4)
return i6
}
func (p *Prefix) lastIPv6Int() ipv6Int {
i := ipToIPv6Int(p.IP)
var m ipv6Int
m.invmask(p.Len())
i[0], i[1] = i[0]|m[0], i[1]|m[1]
return i
}
// Contains reports whether q is a subnetwork of p.
func (p *Prefix) Contains(q *Prefix) bool {
if p.IP.To4() != nil {
return p.containsIPv4(q)
}
if p.IP.To16() != nil && p.IP.To4() == nil {
return p.containsIPv6(q)
}
return false
}
func (p *Prefix) containsIPv4(q *Prefix) bool {
if q.IP.To4() == nil {
return false
}
l := p.Len()
if l >= q.Len() {
return false
}
base := ipToIPv4Int(p.IP.Mask(p.Mask))
mask := ipMaskToIPv4Int(p.Mask)
fip := ipToIPv4Int(q.IP)
lip := q.lastIPv4Int()
fdiff := uint32((base ^ fip) & mask)
ldiff := uint32((base ^ lip) & mask)
return bits.LeadingZeros32(fdiff) >= l && bits.LeadingZeros32(ldiff) >= l
}
func (p *Prefix) containsIPv6(q *Prefix) bool {
if q.IP.To16() == nil || q.IP.To4() != nil {
return false
}
l := p.Len()
if l >= q.Len() {
return false
}
base := ipToIPv6Int(p.IP)
mask := ipMaskToIPv6Int(p.Mask)
l0, l1 := 64, l-64
if l < 64 {
l0, l1 = l, 0
}
fip := ipToIPv6Int(q.IP)
lip := q.lastIPv6Int()
var fdiff, ldiff ipv6Int
fdiff[0], fdiff[1] = (base[0]^fip[0])&mask[0], (base[1]^fip[1])&mask[1]
ldiff[0], ldiff[1] = (base[0]^lip[0])&mask[0], (base[1]^lip[1])&mask[1]
return bits.LeadingZeros64(fdiff[0]) >= l0 && bits.LeadingZeros64(fdiff[1]) >= l1 && bits.LeadingZeros64(ldiff[0]) >= l0 && bits.LeadingZeros64(ldiff[1]) >= l1
}
// Equal reports whether p and q are equal.
func (p *Prefix) Equal(q *Prefix) bool {
return compareAscending(p, q) == 0
}
// Exclude returns a list of prefixes that do not contain q.
func (p *Prefix) Exclude(q *Prefix) []Prefix {
if !p.IPNet.Contains(q.IP) {
return nil
}
if p.Equal(q) {
return []Prefix{*q}
}
subsFn := subnetsIPv6
if p.IP.To4() != nil {
subsFn = subnetsIPv4
}
var ps []Prefix
l, r := subsFn(p, false)
for !l.Equal(q) && !r.Equal(q) {
if l.IPNet.Contains(q.IP) {
ps = append(ps, *r)
l, r = subsFn(l, true)
} else if r.IPNet.Contains(q.IP) {
ps = append(ps, *l)
l, r = subsFn(r, true)
}
}
if l.Equal(q) {
ps = append(ps, *r)
} else if r.Equal(q) {
ps = append(ps, *l)
}
return ps
}
func subnetsIPv4(p *Prefix, reuse bool) (l *Prefix, r *Prefix) {
i := ipToIPv4Int(p.IP) | ipv4Int(1<<uint(IPv4PrefixLen-p.Len()-1))
r = i.prefix(p.Len()+1, IPv4PrefixLen)
if reuse {
l = p
binary.BigEndian.PutUint32(l.Mask, mask32(l.Len()+1))
} else {
l = ipToIPv4Int(p.IP).prefix(p.Len()+1, IPv4PrefixLen)
}
return
}
func subnetsIPv6(p *Prefix, reuse bool) (l *Prefix, r *Prefix) {
i := ipToIPv6Int(p.IP)
id := ipv6Int{0, 1}
id.lsh(IPv6PrefixLen - p.Len() - 1)
ii := ipv6Int{i[0] | id[0], i[1] | id[1]}
r = ii.prefix(p.Len()+1, IPv6PrefixLen)
if reuse {
l = p
var m ipv6Int
m.mask(l.Len() + 1)
binary.BigEndian.PutUint64(l.Mask[:8], m[0])
binary.BigEndian.PutUint64(l.Mask[8:16], m[1])
} else {
l = i.prefix(p.Len()+1, IPv6PrefixLen)
}
return
}
// Hostmask returns a host mask, the inverse mask of p's network mask.
func (p *Prefix) Hostmask() net.IPMask {
return invert(p.Mask)
}
// Last returns the last IP in the address range of p.
// It returns the address of p when p contains only one address.
func (p *Prefix) Last() net.IP {
if p.IP.To4() != nil {
i := p.lastIPv4Int()
return i.ip()
}
if p.IP.To16() != nil && p.IP.To4() == nil {
i := p.lastIPv6Int()
return i.ip()
}
return nil
}
// Len returns the length of p in bits.
func (p *Prefix) Len() int {
l, _ := p.Mask.Size()
return l
}
// MarshalBinary returns a BGP NLRI binary form of p.
func (p *Prefix) MarshalBinary() ([]byte, error) {
ip := p.IP
if p.IP.To4() != nil {
ip = p.IP.To4()
}
var b [1 + net.IPv6len]byte
n := p.Len()
l := ((n + 8 - 1) &^ (8 - 1)) / 8
b[0] = byte(n)
l++
copy(b[1:l], ip)
return b[:l], nil
}
// MarshalText returns a UTF-8-encoded text form of p.
func (p *Prefix) MarshalText() ([]byte, error) {
return []byte(p.String()), nil
}
// NumNodes returns the number of IP node addresses in p.
func (p *Prefix) NumNodes() *big.Int {
i := new(big.Int).SetBytes(invert(p.Mask))
return i.Add(i, big.NewInt(1))
}
// Overlaps reports whether p overlaps with q.
func (p *Prefix) Overlaps(q *Prefix) bool {
return p.Contains(q) || q.Contains(p) || p.Equal(q)
}
func (p Prefix) String() string {
return p.IPNet.String()
}
// Subnets returns a list of prefixes that are split from p, into
// small address blocks by n which represents a number of subnetworks
// in the power of 2 notation.
func (p *Prefix) Subnets(n int) []Prefix {
if 0 > n || n > 17 { // don't bother runtime.makeslice by big numbers
return nil
}
ps := make([]Prefix, 1<<uint(n))
if p.IP.To4() != nil {
x := ipToIPv4Int(p.IP)
off := uint(IPv4PrefixLen - p.Len() - n)
for i := range ps {
ii := x | ipv4Int(i<<off)
ps[i] = *ii.prefix(p.Len()+n, IPv4PrefixLen)
}
return ps
}
x := ipToIPv6Int(p.IP)
off := IPv6PrefixLen - p.Len() - n
for i := range ps {
id := ipv6Int{0, uint64(i)}
id.lsh(off)
ii := ipv6Int{x[0] | id[0], x[1] | id[1]}
ps[i] = *ii.prefix(p.Len()+n, IPv6PrefixLen)
}
return ps
}
// UnmarshalBinary replaces p with the BGP NLRI binary form b.
func (p *Prefix) UnmarshalBinary(b []byte) error {
if p.IP.To4() != nil {
binary.BigEndian.PutUint32(p.Mask, mask32(int(b[0])))
copy(p.IP, net.IPv4zero)
copy(p.IP.To4(), b[1:])
}
if p.IP.To16() != nil && p.IP.To4() == nil {
var m ipv6Int
m.mask(int(b[0]))
binary.BigEndian.PutUint64(p.Mask[:8], m[0])
binary.BigEndian.PutUint64(p.Mask[8:16], m[1])
copy(p.IP, net.IPv6unspecified)
copy(p.IP, b[1:])
}
return nil
}
// UnmarshalText replaces p with txt.
func (p *Prefix) UnmarshalText(txt []byte) error {
_, n, err := net.ParseCIDR(string(txt))
if err != nil {
return err
}
copy(p.IP.To16(), n.IP.To16())
copy(p.Mask, n.Mask)
return nil
}
// Aggregate aggregates ps and returns a list of aggregated prefixes.
func Aggregate(ps []Prefix) []Prefix {
ps = newSortedPrefixes(ps, sortAscending, true)
sortByDescending(ps)
switch len(ps) {
case 0:
return nil
case 1:
return ps[:1]
}
bfFn, superFn := branchingFactorIPv6, supernetIPv6
if ps[0].IP.To4() != nil {
bfFn, superFn = branchingFactorIPv4, supernetIPv4
}
ps = aggregate(aggregateByBF(ps, bfFn, superFn))
sortByAscending(ps)
return ps
}
func aggregateByBF(ps []Prefix, bfFn func([]Prefix) (int, bool), superFn func([]Prefix) *Prefix) []Prefix {
var cont bool
aggrs := ps[:0]
cands := make([]Prefix, 0, len(ps))
for len(ps) > 0 {
l := ps[0].Len()
if l == 0 {
aggrs = append(aggrs, ps[0])
ps = ps[1:]
continue
}
cands = cands[:0]
for i := range ps {
if ps[i].Len() != l {
break
}
cands = append(cands, ps[i])
}
if n, ok := bfFn(cands); !ok {
aggrs = append(aggrs, ps[0])
ps = ps[1:]
} else {
aggrs = append(aggrs, *superFn(cands[:n]))
ps = ps[n:]
cont = true
}
}
sortByDescending(aggrs)
if !cont {
return aggrs
}
return aggregateByBF(aggrs, bfFn, superFn)
}
func aggregate(ps []Prefix) []Prefix {
aggrs := ps[:0]
for i := range ps {
var aggregatable bool
for j := len(ps) - 1; j >= 0; j-- {
if i == j {
continue
}
if ps[j].Contains(&ps[i]) {
aggregatable = true
break
}
}
if aggregatable {
continue
}
aggrs = append(aggrs, ps[i])
}
return aggrs
}
func branchingFactorIPv4(ps []Prefix) (int, bool) {
var lastBF, lastN int
base := ipToIPv4Int(ps[0].IP.Mask(ps[0].Mask))
mask := ipMaskToIPv4Int(ps[0].Mask)
l := ps[0].Len()
for bf := 1; bf < IPv4PrefixLen; bf++ {
n, nfull := 0, 1<<uint(bf)
max := ipv4Int(1 << uint(bf))
aggrMask := mask << uint(bf)
for pat := ipv4Int(0); pat < max; pat++ {
aggr := base&aggrMask | pat<<uint(IPv4PrefixLen-l)
for _, p := range ps {
i := ipToIPv4Int(p.IP)
if aggr == i&mask {
n++
}
}
}
if n < nfull {
break
}
lastBF = bf
lastN = n
}
n := 1 << uint(lastBF)
return n, lastN >= n
}
func branchingFactorIPv6(ps []Prefix) (int, bool) {
var lastBF, lastN int
base := ipToIPv6Int(ps[0].IP)
mask := ipMaskToIPv6Int(ps[0].Mask)
l := ps[0].Len()
for bf := 1; bf < IPv6PrefixLen; bf++ {
n, nfull := 0, 1<<uint(bf)
pat, max := ipv6Int{0, 0}, ipv6Int{0, 1}
max.lsh(bf)
var aggrMask ipv6Int
aggrMask.mask(l - bf)
for ; pat.cmp(&max) < 0; pat.incr() {
npat := pat
npat.lsh(IPv6PrefixLen - l)
var aggr ipv6Int
aggr[0], aggr[1] = base[0]&aggrMask[0]|npat[0], base[1]&aggrMask[1]|npat[1]
for _, p := range ps {
i := ipToIPv6Int(p.IP)
if aggr[0] == i[0]&mask[0] && aggr[1] == i[1]&mask[1] {
n++
}
}
}
if n < nfull {
break
}
lastBF = bf
lastN = n
}
n := 1 << uint(lastBF)
return n, lastN >= n
}
// Compare returns an integer comparing two prefixes.
// The result will be 0 if a == b, -1 if a < b, and +1 if a > b.
func Compare(a, b *Prefix) int {
return compareAscending(a, b)
}
// NewPrefix returns a new prefix.
func NewPrefix(n *net.IPNet) *Prefix {
n.IP = n.IP.To16()
return &Prefix{IPNet: *n}
}
// Summarize summarizes the address range from first to last and
// returns a list of prefixes.
func Summarize(first, last net.IP) []Prefix {
if fip := first.To4(); fip != nil {
lip := last.To4()
if lip == nil {
return nil
}
return summarizeIPv4(fip, lip)
}
if fip := first.To16(); fip != nil && fip.To4() == nil {
lip := last.To16()
if lip == nil || last.To4() != nil {
return nil
}
return summarizeIPv6(fip, lip)
}
return nil
}
const ipv4IntEOR = ipv4Int(math.MaxUint32)
func summarizeIPv4(fip, lip net.IP) []Prefix {
var ps []Prefix
fi, li := ipToIPv4Int(fip), ipToIPv4Int(lip)
for fi.cmp(li) <= 0 {
n := IPv4PrefixLen
for n > 0 {
m := ipv4Int(mask32(n - 1))
l, r := fi&m, fi|ipv4Int(^mask32(n-1))
if fi.cmp(l) != 0 || r.cmp(li) > 0 {
break
}
n--
}
p := fi.prefix(n, IPv4PrefixLen)
ps = append(ps, *p)
fi = p.lastIPv4Int()
if fi == ipv4IntEOR {
break
}
fi++
}
return ps
}
var ipv6IntEOR = ipv6Int{math.MaxUint64, math.MaxUint64}
func summarizeIPv6(fip, lip net.IP) []Prefix {
var ps []Prefix
fi, li := ipToIPv6Int(fip), ipToIPv6Int(lip)
for fi.cmp(&li) <= 0 {
n := IPv6PrefixLen
for n > 0 {
var m ipv6Int
m.mask(n - 1)
l, r := fi, fi
l[0], l[1] = l[0]&m[0], l[1]&m[1]
r.invmask(n - 1)
r[0], r[1] = fi[0]|r[0], fi[1]|r[1]
if fi.cmp(&l) != 0 || r.cmp(&li) > 0 {
break
}
n--
}
p := fi.prefix(n, IPv6PrefixLen)
ps = append(ps, *p)
fi = p.lastIPv6Int()
if fi[0] == ipv6IntEOR[0] && fi[1] == ipv6IntEOR[1] {
break
}
fi.incr()
}
return ps
}
// Supernet finds out a shortest common prefix for ps.
// It returns nil when no suitable prefix is found.
func Supernet(ps []Prefix) *Prefix {
if len(ps) == 0 {
return nil
}
if ps[0].IP.To4() != nil {
ps = byAddrFamily(ps).newIPv4Prefixes()
}
if ps[0].IP.To16() != nil && ps[0].IP.To4() == nil {
ps = byAddrFamily(ps).newIPv6Prefixes()
}
switch len(ps) {
case 0:
return nil
case 1:
return &ps[0]
}
if ps[0].IP.To4() != nil {
return supernetIPv4(ps)
}
if ps[0].IP.To16() != nil && ps[0].IP.To4() == nil {
return supernetIPv6(ps)
}
return nil
}
func supernetIPv4(ps []Prefix) *Prefix {
base := ipToIPv4Int(ps[0].IP.Mask(ps[0].Mask))
mask := ipMaskToIPv4Int(ps[0].Mask)
n := ps[0].Len()
for _, p := range ps[1:] {
i := ipToIPv4Int(p.IP)
if diff := uint32((base ^ i) & mask); diff != 0 {
if l := int(bits.LeadingZeros32(diff)); l < n {
n = l
}
}
}
if n == 0 {
return nil
}
return ipToPrefix(ps[0].IP, n, IPv4PrefixLen)
}
func supernetIPv6(ps []Prefix) *Prefix {
base := ipToIPv6Int(ps[0].IP.Mask(ps[0].Mask))
mask := ipMaskToIPv6Int(ps[0].Mask)
n := ps[0].Len()
var diff ipv6Int
for _, p := range ps[1:] {
i := ipToIPv6Int(p.IP)
diff[0], diff[1] = (base[0]^i[0])&mask[0], (base[1]^i[1])&mask[1]
if diff[0] != 0 {
if l := int(bits.LeadingZeros64(diff[0])); l < n {
n = l
}
} else if diff[1] != 0 {
if l := int(bits.LeadingZeros64(diff[1])); 64+l < n {
n = 64 + l
}
}
}
if n == 0 {
return nil
}
return ipToPrefix(ps[0].IP, n, IPv6PrefixLen)
}
type ipv4Int uint32
func (i ipv4Int) cmp(j ipv4Int) int {
if i < j {
return -1
}
if i > j {
return +1
}
return 0
}
func (i ipv4Int) ip() net.IP {
ip := make(net.IP, net.IPv6len)
copy(ip, net.IPv4zero)
binary.BigEndian.PutUint32(ip.To4(), uint32(i))
return ip.To16()
}
func (i ipv4Int) prefix(l, z int) *Prefix {
ip := i.ip()
m := net.CIDRMask(l, z)
return &Prefix{IPNet: net.IPNet{IP: ip.Mask(m).To16(), Mask: m}}
}
type ipv6Int [2]uint64
func (i *ipv6Int) cmp(j *ipv6Int) int {
if i[0] < j[0] {
return -1
}
if i[0] > j[0] {
return +1
}
if i[1] < j[1] {
return -1
}
if i[1] > j[1] {
return +1
}
return 0
}
func (i *ipv6Int) decr() {
if i[0] == 0 && i[1] == 0 {
return
}
if i[1] > 0 {
i[1]--
} else {
i[0]--
i[1] = math.MaxUint64
}
}
func (i *ipv6Int) incr() {
if i[1] == math.MaxUint64 {
i[0]++
i[1] = 0
} else {
i[1]++
}
}
func (i *ipv6Int) invmask(n int) {
if n > 64 {
i[0], i[1] = ^mask64(64), ^mask64(n-64)
} else {
i[0], i[1] = ^mask64(n), mask64(64)
}
}
func (i *ipv6Int) lsh(n int) {
i[0] = i[0]<<uint(n) | i[1]>>uint(64-n) | i[1]<<uint(n-64)
i[1] = i[1] << uint(n)
}
func (i *ipv6Int) mask(n int) {
if n > 64 {
i[0], i[1] = mask64(64), mask64(n-64)
} else {
i[0], i[1] = mask64(n), 0
}
}
func (i *ipv6Int) ip() net.IP {
ip := make(net.IP, net.IPv6len)
binary.BigEndian.PutUint64(ip[:8], i[0])
binary.BigEndian.PutUint64(ip[8:16], i[1])
return ip
}
func (i *ipv6Int) prefix(l, z int) *Prefix {
ip := i.ip()
m := net.CIDRMask(l, z)
return &Prefix{IPNet: net.IPNet{IP: ip.Mask(m), Mask: m}}
}
func invert(s []byte) []byte {
d := make([]byte, len(s))
for i := range s {
d[i] = ^s[i]
}
return d
}
func ipToIPv4Int(ip net.IP) ipv4Int {
return ipv4Int(binary.BigEndian.Uint32(ip.To4()))
}
func ipToIPv6Int(ip net.IP) ipv6Int {
return ipv6Int{binary.BigEndian.Uint64(ip[:8]), binary.BigEndian.Uint64(ip[8:16])}
}
func ipMaskToIPv4Int(m net.IPMask) ipv4Int {
return ipv4Int(binary.BigEndian.Uint32(m))
}
func ipMaskToIPv6Int(m net.IPMask) ipv6Int {
return ipv6Int{binary.BigEndian.Uint64(m[:8]), binary.BigEndian.Uint64(m[8:16])}
}
func ipToPrefix(s net.IP, l, z int) *Prefix {
d := make(net.IP, net.IPv6len)
copy(d, s.To16())
m := net.CIDRMask(l, z)
return &Prefix{IPNet: net.IPNet{IP: d.Mask(m).To16(), Mask: m}}
}