From 282a6aea1b375d447fdf502c6660e92eb5e19cd4 Mon Sep 17 00:00:00 2001 From: Bruno Dal Bo Date: Mon, 22 Jun 2020 10:30:21 -0700 Subject: Extract common nested LinkEndpoint pattern ... and unify logic for detached netsted endpoints. sniffer.go caused crashes if a packet delivery is attempted when the dispatcher is nil. Extracted the endpoint nesting logic into a common composable type so it can be used by the Fuchsia Netstack (the pattern is widespread there). PiperOrigin-RevId: 317682842 --- pkg/tcpip/link/nested/BUILD | 31 +++++++++ pkg/tcpip/link/nested/nested.go | 131 +++++++++++++++++++++++++++++++++++ pkg/tcpip/link/nested/nested_test.go | 105 ++++++++++++++++++++++++++++ 3 files changed, 267 insertions(+) create mode 100644 pkg/tcpip/link/nested/BUILD create mode 100644 pkg/tcpip/link/nested/nested.go create mode 100644 pkg/tcpip/link/nested/nested_test.go (limited to 'pkg/tcpip/link/nested') diff --git a/pkg/tcpip/link/nested/BUILD b/pkg/tcpip/link/nested/BUILD new file mode 100644 index 000000000..bdd5276ad --- /dev/null +++ b/pkg/tcpip/link/nested/BUILD @@ -0,0 +1,31 @@ +load("//tools:defs.bzl", "go_library", "go_test") + +package(licenses = ["notice"]) + +go_library( + name = "nested", + srcs = [ + "nested.go", + ], + visibility = ["//visibility:public"], + deps = [ + "//pkg/sync", + "//pkg/tcpip", + "//pkg/tcpip/buffer", + "//pkg/tcpip/stack", + ], +) + +go_test( + name = "nested_test", + size = "small", + srcs = [ + "nested_test.go", + ], + deps = [ + "//pkg/tcpip", + "//pkg/tcpip/header", + "//pkg/tcpip/link/nested", + "//pkg/tcpip/stack", + ], +) diff --git a/pkg/tcpip/link/nested/nested.go b/pkg/tcpip/link/nested/nested.go new file mode 100644 index 000000000..2998f9c4f --- /dev/null +++ b/pkg/tcpip/link/nested/nested.go @@ -0,0 +1,131 @@ +// Copyright 2020 The gVisor Authors. +// +// 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 nested provides helpers to implement the pattern of nested +// stack.LinkEndpoints. +package nested + +import ( + "gvisor.dev/gvisor/pkg/sync" + "gvisor.dev/gvisor/pkg/tcpip" + "gvisor.dev/gvisor/pkg/tcpip/buffer" + "gvisor.dev/gvisor/pkg/tcpip/stack" +) + +// Endpoint is a wrapper around stack.LinkEndpoint and stack.NetworkDispatcher +// that can be used to implement nesting safely by providing lifecycle +// concurrency guards. +// +// See the tests in this package for example usage. +type Endpoint struct { + child stack.LinkEndpoint + embedder stack.NetworkDispatcher + + // mu protects dispatcher. + mu sync.RWMutex + dispatcher stack.NetworkDispatcher +} + +var _ stack.GSOEndpoint = (*Endpoint)(nil) +var _ stack.LinkEndpoint = (*Endpoint)(nil) +var _ stack.NetworkDispatcher = (*Endpoint)(nil) + +// Init initializes a nested.Endpoint that uses embedder as the dispatcher for +// child on Attach. +// +// See the tests in this package for example usage. +func (e *Endpoint) Init(child stack.LinkEndpoint, embedder stack.NetworkDispatcher) { + e.child = child + e.embedder = embedder +} + +// DeliverNetworkPacket implements stack.NetworkDispatcher. +func (e *Endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) { + e.mu.RLock() + d := e.dispatcher + e.mu.RUnlock() + if d != nil { + d.DeliverNetworkPacket(remote, local, protocol, pkt) + } +} + +// Attach implements stack.LinkEndpoint. +func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) { + e.mu.Lock() + e.dispatcher = dispatcher + e.mu.Unlock() + // If we're attaching to a valid dispatcher, pass embedder as the dispatcher + // to our child, otherwise detach the child by giving it a nil dispatcher. + var pass stack.NetworkDispatcher + if dispatcher != nil { + pass = e.embedder + } + e.child.Attach(pass) +} + +// IsAttached implements stack.LinkEndpoint. +func (e *Endpoint) IsAttached() bool { + e.mu.RLock() + isAttached := e.dispatcher != nil + e.mu.RUnlock() + return isAttached +} + +// MTU implements stack.LinkEndpoint. +func (e *Endpoint) MTU() uint32 { + return e.child.MTU() +} + +// Capabilities implements stack.LinkEndpoint. +func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities { + return e.child.Capabilities() +} + +// MaxHeaderLength implements stack.LinkEndpoint. +func (e *Endpoint) MaxHeaderLength() uint16 { + return e.child.MaxHeaderLength() +} + +// LinkAddress implements stack.LinkEndpoint. +func (e *Endpoint) LinkAddress() tcpip.LinkAddress { + return e.child.LinkAddress() +} + +// WritePacket implements stack.LinkEndpoint. +func (e *Endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error { + return e.child.WritePacket(r, gso, protocol, pkt) +} + +// WritePackets implements stack.LinkEndpoint. +func (e *Endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) { + return e.child.WritePackets(r, gso, pkts, protocol) +} + +// WriteRawPacket implements stack.LinkEndpoint. +func (e *Endpoint) WriteRawPacket(vv buffer.VectorisedView) *tcpip.Error { + return e.child.WriteRawPacket(vv) +} + +// Wait implements stack.LinkEndpoint. +func (e *Endpoint) Wait() { + e.child.Wait() +} + +// GSOMaxSize implements stack.GSOEndpoint. +func (e *Endpoint) GSOMaxSize() uint32 { + if e, ok := e.child.(stack.GSOEndpoint); ok { + return e.GSOMaxSize() + } + return 0 +} diff --git a/pkg/tcpip/link/nested/nested_test.go b/pkg/tcpip/link/nested/nested_test.go new file mode 100644 index 000000000..c1a219f02 --- /dev/null +++ b/pkg/tcpip/link/nested/nested_test.go @@ -0,0 +1,105 @@ +// Copyright 2020 The gVisor Authors. +// +// 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 nested_test + +import ( + "testing" + + "gvisor.dev/gvisor/pkg/tcpip" + "gvisor.dev/gvisor/pkg/tcpip/header" + "gvisor.dev/gvisor/pkg/tcpip/link/nested" + "gvisor.dev/gvisor/pkg/tcpip/stack" +) + +type parentEndpoint struct { + nested.Endpoint +} + +var _ stack.LinkEndpoint = (*parentEndpoint)(nil) +var _ stack.NetworkDispatcher = (*parentEndpoint)(nil) + +type childEndpoint struct { + stack.LinkEndpoint + dispatcher stack.NetworkDispatcher +} + +var _ stack.LinkEndpoint = (*childEndpoint)(nil) + +func (c *childEndpoint) Attach(dispatcher stack.NetworkDispatcher) { + c.dispatcher = dispatcher +} + +func (c *childEndpoint) IsAttached() bool { + return c.dispatcher != nil +} + +type counterDispatcher struct { + count int +} + +var _ stack.NetworkDispatcher = (*counterDispatcher)(nil) + +func (d *counterDispatcher) DeliverNetworkPacket(tcpip.LinkAddress, tcpip.LinkAddress, tcpip.NetworkProtocolNumber, *stack.PacketBuffer) { + d.count++ +} + +func TestNestedLinkEndpoint(t *testing.T) { + const emptyAddress = tcpip.LinkAddress("") + + var ( + childEP childEndpoint + nestedEP parentEndpoint + disp counterDispatcher + ) + nestedEP.Endpoint.Init(&childEP, &nestedEP) + + if childEP.IsAttached() { + t.Error("On init, childEP.IsAttached() = true, want = false") + } + if nestedEP.IsAttached() { + t.Error("On init, nestedEP.IsAttached() = true, want = false") + } + + nestedEP.Attach(&disp) + if disp.count != 0 { + t.Fatalf("After attach, got disp.count = %d, want = 0", disp.count) + } + if !childEP.IsAttached() { + t.Error("After attach, childEP.IsAttached() = false, want = true") + } + if !nestedEP.IsAttached() { + t.Error("After attach, nestedEP.IsAttached() = false, want = true") + } + + nestedEP.DeliverNetworkPacket(emptyAddress, emptyAddress, header.IPv4ProtocolNumber, &stack.PacketBuffer{}) + if disp.count != 1 { + t.Errorf("After first packet with dispatcher attached, got disp.count = %d, want = 1", disp.count) + } + + nestedEP.Attach(nil) + if childEP.IsAttached() { + t.Error("After detach, childEP.IsAttached() = true, want = false") + } + if nestedEP.IsAttached() { + t.Error("After detach, nestedEP.IsAttached() = true, want = false") + } + + disp.count = 0 + nestedEP.DeliverNetworkPacket(emptyAddress, emptyAddress, header.IPv4ProtocolNumber, &stack.PacketBuffer{}) + if disp.count != 0 { + t.Errorf("After second packet with dispatcher detached, got disp.count = %d, want = 0", disp.count) + } + +} -- cgit v1.2.3