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zhangsz
271
plugins/prefix/plugin.go
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271
plugins/prefix/plugin.go
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// Copyright 2018-present the CoreDHCP Authors. All rights reserved
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// This source code is licensed under the MIT license found in the
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// LICENSE file in the root directory of this source tree.
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// Package prefix implements a plugin offering prefixes to clients requesting them
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// This plugin attributes prefixes to clients requesting them with IA_PREFIX requests.
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//
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// Arguments for the plugin configuration are as follows, in this order:
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// - prefix: The base prefix from which assigned prefixes are carved
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// - max: maximum size of the prefix delegated to clients. When a client requests a larger prefix
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// than this, this is the size of the offered prefix
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package prefix
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// FIXME: various settings will be hardcoded (default size, minimum size, lease times) pending a
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// better configuration system
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import (
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"bytes"
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"errors"
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"fmt"
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"net"
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"strconv"
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"sync"
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"time"
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"github.com/bits-and-blooms/bitset"
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"github.com/insomniacslk/dhcp/dhcpv6"
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dhcpIana "github.com/insomniacslk/dhcp/iana"
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"github.com/coredhcp/coredhcp/handler"
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"github.com/coredhcp/coredhcp/logger"
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"github.com/coredhcp/coredhcp/plugins"
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"github.com/coredhcp/coredhcp/plugins/allocators"
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"github.com/coredhcp/coredhcp/plugins/allocators/bitmap"
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)
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var log = logger.GetLogger("plugins/prefix")
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// Plugin registers the prefix. Prefix delegation only exists for DHCPv6
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var Plugin = plugins.Plugin{
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Name: "prefix",
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Setup6: setupPrefix,
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}
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const leaseDuration = 3600 * time.Second
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func setupPrefix(args ...string) (handler.Handler6, error) {
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// - prefix: 2001:db8::/48 64
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if len(args) < 2 {
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return nil, errors.New("Need both a subnet and an allocation max size")
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}
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_, prefix, err := net.ParseCIDR(args[0])
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if err != nil {
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return nil, fmt.Errorf("Invalid pool subnet: %v", err)
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}
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allocSize, err := strconv.Atoi(args[1])
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if err != nil || allocSize > 128 || allocSize < 0 {
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return nil, fmt.Errorf("Invalid prefix length: %v", err)
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}
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// TODO: select allocators based on heuristics or user configuration
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alloc, err := bitmap.NewBitmapAllocator(*prefix, allocSize)
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if err != nil {
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return nil, fmt.Errorf("Could not initialize prefix allocator: %v", err)
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}
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return (&Handler{
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Records: make(map[string][]lease),
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allocator: alloc,
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}).Handle, nil
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}
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type lease struct {
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Prefix net.IPNet
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Expire time.Time
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}
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// Handler holds state of allocations for the plugin
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type Handler struct {
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// Mutex here is the simplest implementation fit for purpose.
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// We can revisit for perf when we move lease management to separate plugins
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sync.Mutex
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// Records has a string'd []byte as key, because []byte can't be a key itself
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// Since it's not valid utf-8 we can't use any other string function though
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Records map[string][]lease
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allocator allocators.Allocator
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}
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// samePrefix returns true if both prefixes are defined and equal
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// The empty prefix is equal to nothing, not even itself
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func samePrefix(a, b *net.IPNet) bool {
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if a == nil || b == nil {
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return false
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}
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return a.IP.Equal(b.IP) && bytes.Equal(a.Mask, b.Mask)
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}
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// recordKey computes the key for the Records array from the client ID
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func recordKey(d dhcpv6.DUID) string {
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return string(d.ToBytes())
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}
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// Handle processes DHCPv6 packets for the prefix plugin for a given allocator/leaseset
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func (h *Handler) Handle(req, resp dhcpv6.DHCPv6) (dhcpv6.DHCPv6, bool) {
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msg, err := req.GetInnerMessage()
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if err != nil {
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log.Error(err)
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return nil, true
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}
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client := msg.Options.ClientID()
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if client == nil {
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log.Error("Invalid packet received, no clientID")
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return nil, true
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}
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// Each request IA_PD requires an IA_PD response
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for _, iapd := range msg.Options.IAPD() {
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if err != nil {
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log.Errorf("Malformed IAPD received: %v", err)
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resp.AddOption(&dhcpv6.OptStatusCode{StatusCode: dhcpIana.StatusMalformedQuery})
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return resp, true
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}
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iapdResp := &dhcpv6.OptIAPD{
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IaId: iapd.IaId,
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}
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// First figure out what prefixes the client wants
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hints := iapd.Options.Prefixes()
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if len(hints) == 0 {
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// If there are no IAPrefix hints, this is still a valid IA_PD request (just
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// unspecified) and we must attempt to allocate a prefix; so we include an empty hint
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// which is equivalent to no hint
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hints = []*dhcpv6.OptIAPrefix{{Prefix: &net.IPNet{}}}
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}
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// Bitmap to track which requests are already satisfied or not
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satisfied := bitset.New(uint(len(hints)))
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// A possible simple optimization here would be to be able to lock single map values
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// individually instead of the whole map, since we lock for some amount of time
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h.Lock()
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knownLeases := h.Records[recordKey(client)]
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// Bitmap to track which leases are already given in this exchange
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givenOut := bitset.New(uint(len(knownLeases)))
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// This is, for now, a set of heuristics, to reconcile the requests (prefix hints asked
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// by the clients) with what's on offer (existing leases for this client, plus new blocks)
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// Try to find leases that exactly match a hint, and extend them to satisfy the request
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// This is the safest heuristic, if the lease matches exactly we know we aren't missing
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// assigning it to a better candidate request
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for hintIdx, h := range hints {
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for leaseIdx := range knownLeases {
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if samePrefix(h.Prefix, &knownLeases[leaseIdx].Prefix) {
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expire := time.Now().Add(leaseDuration)
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if knownLeases[leaseIdx].Expire.Before(expire) {
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knownLeases[leaseIdx].Expire = expire
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}
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satisfied.Set(uint(hintIdx))
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givenOut.Set(uint(leaseIdx))
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addPrefix(iapdResp, knownLeases[leaseIdx])
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}
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}
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}
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// Then handle the empty hints, by giving out any remaining lease we
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// have already assigned to this client
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for hintIdx, h := range hints {
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if satisfied.Test(uint(hintIdx)) ||
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(h.Prefix != nil && !h.Prefix.IP.Equal(net.IPv6zero)) {
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continue
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}
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for leaseIdx, l := range knownLeases {
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if givenOut.Test(uint(leaseIdx)) {
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continue
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}
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// If a length was requested, only give out prefixes of that length
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// This is a bad heuristic depending on the allocator behavior, to be improved
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if hintPrefixLen, _ := h.Prefix.Mask.Size(); hintPrefixLen != 0 {
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leasePrefixLen, _ := l.Prefix.Mask.Size()
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if hintPrefixLen != leasePrefixLen {
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continue
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}
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}
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expire := time.Now().Add(leaseDuration)
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if knownLeases[leaseIdx].Expire.Before(expire) {
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knownLeases[leaseIdx].Expire = expire
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}
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satisfied.Set(uint(hintIdx))
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givenOut.Set(uint(leaseIdx))
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addPrefix(iapdResp, knownLeases[leaseIdx])
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}
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}
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// Now remains requests with a hint that we can't trivially satisfy, and possibly expired
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// leases that haven't been explicitly requested again.
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// A possible improvement here would be to try to widen existing leases, to satisfy wider
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// requests that contain an existing leases; and to try to break down existing leases into
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// smaller allocations, to satisfy requests for a subnet of an existing lease
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// We probably don't need such complex behavior (the vast majority of requests will come
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// with an empty, or length-only hint)
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// Assign a new lease to satisfy the request
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var newLeases []lease
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for i, prefix := range hints {
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if satisfied.Test(uint(i)) {
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continue
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}
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if prefix.Prefix == nil {
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// XXX: replace usage of dhcp.OptIAPrefix with a better struct in this inner
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// function to avoid repeated nullpointer checks
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prefix.Prefix = &net.IPNet{}
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}
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allocated, err := h.allocator.Allocate(*prefix.Prefix)
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if err != nil {
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log.Debugf("Nothing allocated for hinted prefix %s", prefix)
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continue
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}
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l := lease{
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Expire: time.Now().Add(leaseDuration),
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Prefix: allocated,
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}
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addPrefix(iapdResp, l)
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newLeases = append(knownLeases, l)
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log.Debugf("Allocated %s to %s (IAID: %x)", &allocated, client, iapd.IaId)
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}
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if newLeases != nil {
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h.Records[recordKey(client)] = newLeases
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}
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h.Unlock()
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if len(iapdResp.Options.Options) == 0 {
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log.Debugf("No valid prefix to return for IAID %x", iapd.IaId)
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iapdResp.Options.Add(&dhcpv6.OptStatusCode{
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StatusCode: dhcpIana.StatusNoPrefixAvail,
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})
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}
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resp.AddOption(iapdResp)
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}
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return resp, false
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}
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func addPrefix(resp *dhcpv6.OptIAPD, l lease) {
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lifetime := time.Until(l.Expire)
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resp.Options.Add(&dhcpv6.OptIAPrefix{
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PreferredLifetime: lifetime,
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ValidLifetime: lifetime,
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Prefix: dup(&l.Prefix),
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})
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}
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func dup(src *net.IPNet) (dst *net.IPNet) {
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dst = &net.IPNet{
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IP: make(net.IP, net.IPv6len),
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Mask: make(net.IPMask, net.IPv6len),
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}
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copy(dst.IP, src.IP)
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copy(dst.Mask, src.Mask)
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return dst
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}
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