add all files from Hong

plugins/allocators/bitmap/bitmap.go

@@ -0,0 +1,135 @@
+// 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.
+
+// This allocator only returns prefixes of a single size
+// This is much simpler to implement (reduces the problem to an equivalent of
+// single ip allocations), probably makes sense in cases where the available
+// range is much larger than the expected number of clients. Also is what KEA
+// does so at least it's not worse than that
+
+package bitmap
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"strconv"
+	"sync"
+
+	"github.com/bits-and-blooms/bitset"
+
+	"github.com/coredhcp/coredhcp/logger"
+	"github.com/coredhcp/coredhcp/plugins/allocators"
+)
+
+var log = logger.GetLogger("plugins/allocators/bitmap")
+
+// Allocator is a prefix allocator allocating in chunks of a fixed size
+// regardless of the size requested by the client.
+// It consumes an amount of memory proportional to the total amount of available prefixes
+type Allocator struct {
+	containing net.IPNet
+	page       int
+	bitmap     *bitset.BitSet
+	l          sync.Mutex
+}
+
+// prefix must verify: containing.Mask.Size < prefix.Mask.Size < page
+func (a *Allocator) toIndex(base net.IP) (uint, error) {
+	value, err := allocators.Offset(base, a.containing.IP, a.page)
+	if err != nil {
+		return 0, fmt.Errorf("Cannot compute prefix index: %w", err)
+	}
+
+	return uint(value), nil
+}
+
+func (a *Allocator) toPrefix(idx uint) (net.IP, error) {
+	return allocators.AddPrefixes(a.containing.IP, uint64(idx), uint64(a.page))
+}
+
+// Allocate reserves a maxsize-sized block and returns a block of size
+// min(maxsize, hint.size)
+func (a *Allocator) Allocate(hint net.IPNet) (ret net.IPNet, err error) {
+
+	// Ensure size is max(maxsize, hint.size)
+	reqSize, hintErr := hint.Mask.Size()
+	if reqSize < a.page || hintErr != 128 {
+		reqSize = a.page
+	}
+	ret.Mask = net.CIDRMask(reqSize, 128)
+
+	// Try to allocate the requested prefix
+	a.l.Lock()
+	defer a.l.Unlock()
+	if hint.IP.To16() != nil && a.containing.Contains(hint.IP) {
+		idx, hintErr := a.toIndex(hint.IP)
+		if hintErr == nil && !a.bitmap.Test(idx) {
+			a.bitmap.Set(idx)
+			ret.IP, err = a.toPrefix(idx)
+			return
+		}
+	}
+
+	// Find a free prefix
+	next, ok := a.bitmap.NextClear(0)
+	if !ok {
+		err = allocators.ErrNoAddrAvail
+		return
+	}
+	a.bitmap.Set(next)
+	ret.IP, err = a.toPrefix(next)
+	if err != nil {
+		// This violates the assumption that every index in the bitmap maps back to a valid prefix
+		err = fmt.Errorf("BUG: could not get prefix from allocation: %w", err)
+		a.bitmap.Clear(next)
+	}
+	return
+}
+
+// Free returns the given prefix to the available pool if it was taken.
+func (a *Allocator) Free(prefix net.IPNet) error {
+	idx, err := a.toIndex(prefix.IP.Mask(prefix.Mask))
+	if err != nil {
+		return fmt.Errorf("Could not find prefix in pool: %w", err)
+	}
+
+	a.l.Lock()
+	defer a.l.Unlock()
+
+	if !a.bitmap.Test(idx) {
+		return &allocators.ErrDoubleFree{Loc: prefix}
+	}
+	a.bitmap.Clear(idx)
+	return nil
+}
+
+// NewBitmapAllocator creates a new allocator, allocating /`size` prefixes
+// carved out of the given `pool` prefix
+func NewBitmapAllocator(pool net.IPNet, size int) (*Allocator, error) {
+
+	poolSize, _ := pool.Mask.Size()
+	allocOrder := size - poolSize
+
+	if allocOrder < 0 {
+		return nil, errors.New("The size of allocated prefixes cannot be larger than the pool they're allocated from")
+	} else if allocOrder >= strconv.IntSize {
+		return nil, fmt.Errorf("A pool with more than 2^%d items is not representable", size-poolSize)
+	} else if allocOrder >= 32 {
+		log.Warningln("Using a pool of more than 2^32 elements may result in large memory consumption")
+	}
+
+	if !(1<<uint(allocOrder) <= bitset.Cap()) {
+		return nil, errors.New("Can't fit this pool using the bitmap allocator")
+	}
+
+	alloc := Allocator{
+		containing: pool,
+		page:       size,
+
+		bitmap: bitset.New(1 << uint(allocOrder)),
+	}
+
+	return &alloc, nil
+}