138 lines
4.4 KiB
Go
138 lines
4.4 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package pipe provides the implementation of pipe-like data-link layer
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// endpoints. Such endpoints allow packets to be sent between two interfaces.
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package pipe
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import (
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"gvisor.dev/gvisor/pkg/tcpip"
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"gvisor.dev/gvisor/pkg/tcpip/buffer"
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"gvisor.dev/gvisor/pkg/tcpip/header"
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"gvisor.dev/gvisor/pkg/tcpip/stack"
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)
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var _ stack.LinkEndpoint = (*Endpoint)(nil)
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// New returns both ends of a new pipe.
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func New(linkAddr1, linkAddr2 tcpip.LinkAddress) (*Endpoint, *Endpoint) {
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ep1 := &Endpoint{
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linkAddr: linkAddr1,
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}
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ep2 := &Endpoint{
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linkAddr: linkAddr2,
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}
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ep1.linked = ep2
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ep2.linked = ep1
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return ep1, ep2
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}
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// Endpoint is one end of a pipe.
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type Endpoint struct {
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dispatcher stack.NetworkDispatcher
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linked *Endpoint
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linkAddr tcpip.LinkAddress
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}
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func (e *Endpoint) deliverPackets(r stack.RouteInfo, proto tcpip.NetworkProtocolNumber, pkts stack.PacketBufferList) {
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// Note that the local address from the perspective of this endpoint is the
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// remote address from the perspective of the other end of the pipe
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// (e.linked). Similarly, the remote address from the perspective of this
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// endpoint is the local address on the other end.
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//
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// Deliver the packet in a new goroutine to escape this goroutine's stack and
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// avoid a deadlock when a packet triggers a response which leads the stack to
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// try and take a lock it already holds.
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//
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// As of writing, a deadlock may occur when performing link resolution as the
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// neighbor table will send a solicitation while holding a lock and the
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// response advertisement will be sent in the same stack that sent the
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// solictation. When the response is received, the stack attempts to take the
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// same lock it already took before sending the solicitation, leading to a
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// deadlock. Basically, we attempt to lock the same lock twice in the same
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// call stack.
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//
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// TODO(gvisor.dev/issue/5289): don't use a new goroutine once we support send
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// and receive queues.
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go func() {
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for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
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e.linked.dispatcher.DeliverNetworkPacket(r.LocalLinkAddress /* remote */, r.RemoteLinkAddress /* local */, proto, stack.NewPacketBuffer(stack.PacketBufferOptions{
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Data: buffer.NewVectorisedView(pkt.Size(), pkt.Views()),
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}))
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}
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}()
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}
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// WritePacket implements stack.LinkEndpoint.
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func (e *Endpoint) WritePacket(r stack.RouteInfo, _ *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
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if e.linked.IsAttached() {
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var pkts stack.PacketBufferList
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pkts.PushBack(pkt)
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e.deliverPackets(r, proto, pkts)
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}
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return nil
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}
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// WritePackets implements stack.LinkEndpoint.
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func (e *Endpoint) WritePackets(r stack.RouteInfo, _ *stack.GSO, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
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if e.linked.IsAttached() {
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e.deliverPackets(r, proto, pkts)
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}
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return pkts.Len(), nil
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}
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// Attach implements stack.LinkEndpoint.
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func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
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e.dispatcher = dispatcher
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}
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// IsAttached implements stack.LinkEndpoint.
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func (e *Endpoint) IsAttached() bool {
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return e.dispatcher != nil
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}
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// Wait implements stack.LinkEndpoint.
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func (*Endpoint) Wait() {}
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// MTU implements stack.LinkEndpoint.
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func (*Endpoint) MTU() uint32 {
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return header.IPv6MinimumMTU
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}
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// Capabilities implements stack.LinkEndpoint.
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func (*Endpoint) Capabilities() stack.LinkEndpointCapabilities {
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return 0
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}
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// MaxHeaderLength implements stack.LinkEndpoint.
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func (*Endpoint) MaxHeaderLength() uint16 {
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return 0
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}
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// LinkAddress implements stack.LinkEndpoint.
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func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
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return e.linkAddr
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}
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// ARPHardwareType implements stack.LinkEndpoint.
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func (*Endpoint) ARPHardwareType() header.ARPHardwareType {
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return header.ARPHardwareNone
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}
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// AddHeader implements stack.LinkEndpoint.
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func (*Endpoint) AddHeader(_, _ tcpip.LinkAddress, _ tcpip.NetworkProtocolNumber, _ *stack.PacketBuffer) {
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}
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