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// 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 ethernet provides an implementation of an ethernet link endpoint that
// wraps an inner link endpoint.
package ethernet
import (
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/pkg/tcpip/link/nested"
"gvisor.dev/gvisor/pkg/tcpip/stack"
)
var _ stack.NetworkDispatcher = (*Endpoint)(nil)
var _ stack.LinkEndpoint = (*Endpoint)(nil)
// New returns an ethernet link endpoint that wraps an inner link endpoint.
func New(ep stack.LinkEndpoint) *Endpoint {
var e Endpoint
e.Endpoint.Init(ep, &e)
return &e
}
// Endpoint is an ethernet endpoint.
//
// It adds an ethernet header to packets before sending them out through its
// inner link endpoint and consumes an ethernet header before sending the
// packet to the stack.
type Endpoint struct {
nested.Endpoint
}
// LinkAddress implements stack.LinkEndpoint.
func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
if l := e.Endpoint.LinkAddress(); len(l) != 0 {
return l
}
return header.UnspecifiedEthernetAddress
}
// DeliverNetworkPacket implements stack.NetworkDispatcher.
func (e *Endpoint) DeliverNetworkPacket(_, _ tcpip.LinkAddress, _ tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
hdr, ok := pkt.LinkHeader().Consume(header.EthernetMinimumSize)
if !ok {
return
}
// Note, there is no need to check the destination link address here since
// the ethernet hardware filters frames based on their destination addresses.
eth := header.Ethernet(hdr)
e.Endpoint.DeliverNetworkPacket(eth.SourceAddress() /* remote */, eth.DestinationAddress() /* local */, eth.Type() /* protocol */, pkt)
}
// Capabilities implements stack.LinkEndpoint.
func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
c := e.Endpoint.Capabilities()
if c&stack.CapabilityLoopback == 0 {
c |= stack.CapabilityResolutionRequired
}
return c
}
// WritePacket implements stack.LinkEndpoint.
func (e *Endpoint) WritePacket(r stack.RouteInfo, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
e.AddHeader(e.LinkAddress(), r.RemoteLinkAddress, proto, pkt)
return e.Endpoint.WritePacket(r, proto, pkt)
}
// WritePackets implements stack.LinkEndpoint.
func (e *Endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, proto tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
linkAddr := e.LinkAddress()
for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
e.AddHeader(linkAddr, r.RemoteLinkAddress, proto, pkt)
}
return e.Endpoint.WritePackets(r, pkts, proto)
}
// MaxHeaderLength implements stack.LinkEndpoint.
func (e *Endpoint) MaxHeaderLength() uint16 {
return header.EthernetMinimumSize + e.Endpoint.MaxHeaderLength()
}
// ARPHardwareType implements stack.LinkEndpoint.
func (e *Endpoint) ARPHardwareType() header.ARPHardwareType {
if a := e.Endpoint.ARPHardwareType(); a != header.ARPHardwareNone {
return a
}
return header.ARPHardwareEther
}
// AddHeader implements stack.LinkEndpoint.
func (*Endpoint) AddHeader(local, remote tcpip.LinkAddress, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
eth := header.Ethernet(pkt.LinkHeader().Push(header.EthernetMinimumSize))
fields := header.EthernetFields{
SrcAddr: local,
DstAddr: remote,
Type: proto,
}
eth.Encode(&fields)
}
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