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// Copyright 2016 The Netstack Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ipv4
import (
"encoding/binary"
"gvisor.googlesource.com/gvisor/pkg/tcpip"
"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
)
// handleControl handles the case when an ICMP packet contains the headers of
// the original packet that caused the ICMP one to be sent. This information is
// used to find out which transport endpoint must be notified about the ICMP
// packet.
func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, vv *buffer.VectorisedView) {
h := header.IPv4(vv.First())
// We don't use IsValid() here because ICMP only requires that the IP
// header plus 8 bytes of the transport header be included. So it's
// likely that it is truncated, which would cause IsValid to return
// false.
//
// Drop packet if it doesn't have the basic IPv4 header or if the
// original source address doesn't match the endpoint's address.
if len(h) < header.IPv4MinimumSize || h.SourceAddress() != e.id.LocalAddress {
return
}
hlen := int(h.HeaderLength())
if vv.Size() < hlen || h.FragmentOffset() != 0 {
// We won't be able to handle this if it doesn't contain the
// full IPv4 header, or if it's a fragment not at offset 0
// (because it won't have the transport header).
return
}
// Skip the ip header, then deliver control message.
vv.TrimFront(hlen)
p := h.TransportProtocol()
e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, vv)
}
func (e *endpoint) handleICMP(r *stack.Route, vv *buffer.VectorisedView) {
v := vv.First()
if len(v) < header.ICMPv4MinimumSize {
return
}
h := header.ICMPv4(v)
switch h.Type() {
case header.ICMPv4Echo:
if len(v) < header.ICMPv4EchoMinimumSize {
return
}
vv.TrimFront(header.ICMPv4MinimumSize)
req := echoRequest{r: r.Clone(), v: vv.ToView()}
select {
case e.echoRequests <- req:
default:
req.r.Release()
}
case header.ICMPv4EchoReply:
if len(v) < header.ICMPv4EchoMinimumSize {
return
}
e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, vv)
case header.ICMPv4DstUnreachable:
if len(v) < header.ICMPv4DstUnreachableMinimumSize {
return
}
vv.TrimFront(header.ICMPv4DstUnreachableMinimumSize)
switch h.Code() {
case header.ICMPv4PortUnreachable:
e.handleControl(stack.ControlPortUnreachable, 0, vv)
case header.ICMPv4FragmentationNeeded:
mtu := uint32(binary.BigEndian.Uint16(v[header.ICMPv4DstUnreachableMinimumSize-2:]))
e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), vv)
}
}
// TODO: Handle other ICMP types.
}
type echoRequest struct {
r stack.Route
v buffer.View
}
func (e *endpoint) echoReplier() {
for req := range e.echoRequests {
sendPing4(&req.r, 0, req.v)
req.r.Release()
}
}
func sendPing4(r *stack.Route, code byte, data buffer.View) *tcpip.Error {
hdr := buffer.NewPrependable(header.ICMPv4EchoMinimumSize + int(r.MaxHeaderLength()))
icmpv4 := header.ICMPv4(hdr.Prepend(header.ICMPv4EchoMinimumSize))
icmpv4.SetType(header.ICMPv4EchoReply)
icmpv4.SetCode(code)
copy(icmpv4[header.ICMPv4MinimumSize:], data)
data = data[header.ICMPv4EchoMinimumSize-header.ICMPv4MinimumSize:]
icmpv4.SetChecksum(^header.Checksum(icmpv4, header.Checksum(data, 0)))
return r.WritePacket(&hdr, data, header.ICMPv4ProtocolNumber)
}
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