118 lines
2.9 KiB
Go
118 lines
2.9 KiB
Go
package dhcpd
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import (
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"fmt"
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"math"
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"math/big"
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"net"
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"github.com/AdguardTeam/golibs/errors"
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)
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// ipRange is an inclusive range of IP addresses. A nil range is a range that
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// doesn't contain any IP addresses.
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//
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// It is safe for concurrent use.
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//
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// TODO(a.garipov): Perhaps create an optimised version with uint32 for
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// IPv4 ranges? Or use one of uint128 packages?
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type ipRange struct {
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start *big.Int
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end *big.Int
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}
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// maxRangeLen is the maximum IP range length. The bitsets used in servers only
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// accept uints, which can have the size of 32 bit.
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const maxRangeLen = math.MaxUint32
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// newIPRange creates a new IP address range. start must be less than end. The
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// resulting range must not be greater than maxRangeLen.
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func newIPRange(start, end net.IP) (r *ipRange, err error) {
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defer func() { err = errors.Annotate(err, "invalid ip range: %w") }()
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// Make sure that both are 16 bytes long to simplify handling in
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// methods.
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start, end = start.To16(), end.To16()
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startInt := (&big.Int{}).SetBytes(start)
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endInt := (&big.Int{}).SetBytes(end)
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diff := (&big.Int{}).Sub(endInt, startInt)
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if diff.Sign() <= 0 {
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return nil, fmt.Errorf("start is greater than or equal to end")
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} else if !diff.IsUint64() || diff.Uint64() > maxRangeLen {
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return nil, fmt.Errorf("range is too large")
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}
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r = &ipRange{
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start: startInt,
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end: endInt,
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}
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return r, nil
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}
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// contains returns true if r contains ip.
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func (r *ipRange) contains(ip net.IP) (ok bool) {
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if r == nil {
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return false
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}
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ipInt := (&big.Int{}).SetBytes(ip.To16())
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return r.containsInt(ipInt)
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}
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// containsInt returns true if r contains ipInt. For internal use only.
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func (r *ipRange) containsInt(ipInt *big.Int) (ok bool) {
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return ipInt.Cmp(r.start) >= 0 && ipInt.Cmp(r.end) <= 0
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}
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// ipPredicate is a function that is called on every IP address in
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// (*ipRange).find. ip is given in the 16-byte form.
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type ipPredicate func(ip net.IP) (ok bool)
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// find finds the first IP address in r for which p returns true. ip is in the
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// 16-byte form.
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func (r *ipRange) find(p ipPredicate) (ip net.IP) {
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if r == nil {
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return nil
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}
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ip = make(net.IP, net.IPv6len)
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_1 := big.NewInt(1)
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for i := (&big.Int{}).Set(r.start); i.Cmp(r.end) <= 0; i.Add(i, _1) {
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i.FillBytes(ip)
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if p(ip) {
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return ip
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}
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}
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return nil
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}
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// offset returns the offset of ip from the beginning of r. It returns 0 and
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// false if ip is not in r.
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func (r *ipRange) offset(ip net.IP) (offset uint64, ok bool) {
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if r == nil {
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return 0, false
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}
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ip = ip.To16()
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ipInt := (&big.Int{}).SetBytes(ip)
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if !r.containsInt(ipInt) {
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return 0, false
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}
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offsetInt := (&big.Int{}).Sub(ipInt, r.start)
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// Assume that the range was checked against maxRangeLen during
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// construction.
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return offsetInt.Uint64(), true
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}
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// String implements the fmt.Stringer interface for *ipRange.
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func (r *ipRange) String() (s string) {
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return fmt.Sprintf("%s-%s", r.start, r.end)
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}
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