| /* |
| * Copyright 2018-present Open Networking Foundation |
| |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package flow |
| |
| import ( |
| "context" |
| "sync" |
| |
| ofp "github.com/opencord/voltha-protos/v4/go/openflow_13" |
| ) |
| |
| // Cache hides all low-level locking & synchronization related to flow state updates |
| type Cache struct { |
| // this lock protects the flows map, it does not protect individual flows |
| lock sync.RWMutex |
| flows map[uint64]*chunk |
| } |
| |
| // chunk keeps a flow and the lock for this flow |
| type chunk struct { |
| // this lock is used to synchronize all access to the flow, and also to the "deleted" variable |
| lock sync.Mutex |
| deleted bool |
| |
| flow *ofp.OfpFlowStats |
| } |
| |
| func NewCache() *Cache { |
| return &Cache{ |
| flows: make(map[uint64]*chunk), |
| } |
| } |
| |
| // LockOrCreate locks this flow if it exists, or creates a new flow if it does not. |
| // In the case of flow creation, the provided "flow" must not be modified afterwards. |
| func (cache *Cache) LockOrCreate(ctx context.Context, flow *ofp.OfpFlowStats) (*Handle, bool, error) { |
| // try to use read lock instead of full lock if possible |
| if handle, have := cache.Lock(flow.Id); have { |
| return handle, false, nil |
| } |
| |
| cache.lock.Lock() |
| entry, have := cache.flows[flow.Id] |
| if !have { |
| entry := &chunk{flow: flow} |
| cache.flows[flow.Id] = entry |
| entry.lock.Lock() |
| cache.lock.Unlock() |
| |
| return &Handle{loader: cache, chunk: entry}, true, nil |
| } |
| cache.lock.Unlock() |
| |
| entry.lock.Lock() |
| if entry.deleted { |
| entry.lock.Unlock() |
| return cache.LockOrCreate(ctx, flow) |
| } |
| return &Handle{loader: cache, chunk: entry}, false, nil |
| } |
| |
| // Lock acquires the lock for this flow, and returns a handle which can be used to access the flow until it's unlocked. |
| // This handle ensures that the flow cannot be accessed if the lock is not held. |
| // Returns false if the flow is not present. |
| // TODO: consider accepting a ctx and aborting the lock attempt on cancellation |
| func (cache *Cache) Lock(id uint64) (*Handle, bool) { |
| cache.lock.RLock() |
| entry, have := cache.flows[id] |
| cache.lock.RUnlock() |
| |
| if !have { |
| return nil, false |
| } |
| |
| entry.lock.Lock() |
| if entry.deleted { |
| entry.lock.Unlock() |
| return cache.Lock(id) |
| } |
| return &Handle{loader: cache, chunk: entry}, true |
| } |
| |
| // Handle is allocated for each Lock() call, all modifications are made using it, and it is invalidated by Unlock() |
| // This enforces correct Lock()-Usage()-Unlock() ordering. |
| type Handle struct { |
| loader *Cache |
| chunk *chunk |
| } |
| |
| // GetReadOnly returns an *ofp.OfpFlowStats which MUST NOT be modified externally, but which is safe to keep indefinitely |
| func (h *Handle) GetReadOnly() *ofp.OfpFlowStats { |
| return h.chunk.flow |
| } |
| |
| // Update updates an existing flow in cache. |
| // The provided "flow" must not be modified afterwards. |
| func (h *Handle) Update(ctx context.Context, flow *ofp.OfpFlowStats) error { |
| h.chunk.flow = flow |
| return nil |
| } |
| |
| // Delete removes the flow from the cache |
| func (h *Handle) Delete(ctx context.Context) error { |
| h.chunk.deleted = true |
| |
| h.loader.lock.Lock() |
| delete(h.loader.flows, h.chunk.flow.Id) |
| h.loader.lock.Unlock() |
| |
| h.Unlock() |
| return nil |
| } |
| |
| // Unlock releases the lock on the flow |
| func (h *Handle) Unlock() { |
| if h.chunk != nil { |
| h.chunk.lock.Unlock() |
| h.chunk = nil // attempting to access the flow through this handle in future will panic |
| } |
| } |
| |
| // ListIDs returns a snapshot of all the managed flow IDs |
| // TODO: iterating through flows safely is expensive now, since all flows are stored & locked separately |
| // should avoid this where possible |
| func (cache *Cache) ListIDs() map[uint64]struct{} { |
| cache.lock.RLock() |
| defer cache.lock.RUnlock() |
| // copy the IDs so caller can safely iterate |
| ret := make(map[uint64]struct{}, len(cache.flows)) |
| for id := range cache.flows { |
| ret[id] = struct{}{} |
| } |
| return ret |
| } |