add all files from Hong

plugins/allocators/allocator.go

@@ -0,0 +1,48 @@
+// Copyright 2018-present the CoreDHCP Authors. All rights reserved
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+
+// Package allocators provides the interface and the algorithm(s) for allocation of ipv6
+// prefixes of various sizes within a larger prefix.
+// There are many many parallels with memory allocation.
+package allocators
+
+import (
+	"errors"
+	"fmt"
+	"net"
+)
+
+// Allocator is the interface to the address allocator. It only finds and
+// allocates blocks and is not concerned with lease-specific questions like
+// expiration (ie garbage collection needs to be handled separately)
+type Allocator interface {
+	// Allocate finds a suitable prefix of the given size and returns it.
+	//
+	// hint is a prefix, which the client desires especially, and that the
+	// allocator MAY try to return; the allocator SHOULD try to return a prefix of
+	// the same size as the given hint prefix. The allocator MUST NOT return an
+	// error if a prefix was successfully assigned, even if the prefix has nothing
+	// in common with the hinted prefix
+	Allocate(hint net.IPNet) (net.IPNet, error)
+
+	// Free returns the prefix containing the given network to the pool
+	//
+	// Free may return a DoubleFreeError if the prefix being returned was not
+	// previously allocated
+	Free(net.IPNet) error
+}
+
+// ErrDoubleFree is an error type returned by Allocator.Free() when a
+// non-allocated block is passed
+type ErrDoubleFree struct {
+	Loc net.IPNet
+}
+
+// String returns a human-readable error message for a DoubleFree error
+func (err *ErrDoubleFree) Error() string {
+	return fmt.Sprint("Attempted to free unallocated block at ", err.Loc.String())
+}
+
+// ErrNoAddrAvail is returned when we can't allocate an IP because there's no unallocated space left
+var ErrNoAddrAvail = errors.New("no address available to allocate")