99 lines
2.7 KiB
Go
99 lines
2.7 KiB
Go
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package dhcpsvc
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import (
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"encoding/binary"
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"fmt"
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"math"
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"math/big"
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"net/netip"
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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 zero range doesn't contain
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// any IP addresses.
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//
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// It is safe for concurrent use.
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type ipRange struct {
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start netip.Addr
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end netip.Addr
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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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//
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// TODO(a.garipov, e.burkov): Reconsider the value for IPv6.
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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 netip.Addr) (r ipRange, err error) {
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defer func() { err = errors.Annotate(err, "invalid ip range: %w") }()
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switch false {
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case start.Is4() == end.Is4():
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return ipRange{}, fmt.Errorf("%s and %s must be within the same address family", start, end)
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case start.Less(end):
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return ipRange{}, fmt.Errorf("start %s is greater than or equal to end %s", start, end)
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default:
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diff := (&big.Int{}).Sub(
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(&big.Int{}).SetBytes(end.AsSlice()),
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(&big.Int{}).SetBytes(start.AsSlice()),
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)
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if !diff.IsUint64() || diff.Uint64() > maxRangeLen {
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return ipRange{}, fmt.Errorf("range length must be within %d", uint32(maxRangeLen))
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}
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}
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return ipRange{
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start: start,
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end: end,
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}, 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 netip.Addr) (ok bool) {
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// Assume that the end was checked to be within the same address family as
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// the start during construction.
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return r.start.Is4() == ip.Is4() && !ip.Less(r.start) && !r.end.Less(ip)
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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].
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type ipPredicate func(ip netip.Addr) (ok bool)
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// find finds the first IP address in r for which p returns true. It returns an
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// empty [netip.Addr] if there are no addresses that satisfy p.
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//
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// TODO(e.burkov): Use.
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func (r ipRange) find(p ipPredicate) (ip netip.Addr) {
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for ip = r.start; !r.end.Less(ip); ip = ip.Next() {
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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 netip.Addr{}
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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 netip.Addr) (offset uint64, ok bool) {
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if !r.contains(ip) {
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return 0, false
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}
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startData, ipData := r.start.As16(), ip.As16()
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be := binary.BigEndian
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// Assume that the range length was checked against maxRangeLen during
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// construction.
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return be.Uint64(ipData[8:]) - be.Uint64(startData[8:]), 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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