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// Copyright 2018 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 ipv4
import (
"gvisor.dev/gvisor/pkg/tcpip/buffer"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/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, pkt *stack.PacketBuffer) {
h, ok := pkt.Data.PullUp(header.IPv4MinimumSize)
if !ok {
return
}
hdr := header.IPv4(h)
// 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 an address we own.
src := hdr.SourceAddress()
if e.stack.CheckLocalAddress(e.NICID(), ProtocolNumber, src) == 0 {
return
}
hlen := int(hdr.HeaderLength())
if pkt.Data.Size() < hlen || hdr.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.
pkt.Data.TrimFront(hlen)
p := hdr.TransportProtocol()
e.dispatcher.DeliverTransportControlPacket(src, hdr.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt)
}
func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) {
stats := r.Stats()
received := stats.ICMP.V4PacketsReceived
// TODO(gvisor.dev/issue/170): ICMP packets don't have their
// TransportHeader fields set. See icmp/protocol.go:protocol.Parse for a
// full explanation.
v, ok := pkt.Data.PullUp(header.ICMPv4MinimumSize)
if !ok {
received.Invalid.Increment()
return
}
h := header.ICMPv4(v)
// TODO(b/112892170): Meaningfully handle all ICMP types.
switch h.Type() {
case header.ICMPv4Echo:
received.Echo.Increment()
// Only send a reply if the checksum is valid.
wantChecksum := h.Checksum()
// Reset the checksum field to 0 to can calculate the proper
// checksum. We'll have to reset this before we hand the packet
// off.
h.SetChecksum(0)
gotChecksum := ^header.ChecksumVV(pkt.Data, 0 /* initial */)
if gotChecksum != wantChecksum {
// It's possible that a raw socket expects to receive this.
h.SetChecksum(wantChecksum)
e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt)
received.Invalid.Increment()
return
}
// Make a copy of data before pkt gets sent to raw socket.
// DeliverTransportPacket will take ownership of pkt.
replyData := pkt.Data.Clone(nil)
replyData.TrimFront(header.ICMPv4MinimumSize)
// It's possible that a raw socket expects to receive this.
h.SetChecksum(wantChecksum)
e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt)
remoteLinkAddr := r.RemoteLinkAddress
// As per RFC 1122 section 3.2.1.3, when a host sends any datagram, the IP
// source address MUST be one of its own IP addresses (but not a broadcast
// or multicast address).
localAddr := r.LocalAddress
if r.IsInboundBroadcast() || header.IsV4MulticastAddress(r.LocalAddress) {
localAddr = ""
}
r, err := r.Stack().FindRoute(e.NICID(), localAddr, r.RemoteAddress, ProtocolNumber, false /* multicastLoop */)
if err != nil {
// If we cannot find a route to the destination, silently drop the packet.
return
}
defer r.Release()
// Use the remote link address from the incoming packet.
r.ResolveWith(remoteLinkAddr)
// Prepare a reply packet.
icmpHdr := make(header.ICMPv4, header.ICMPv4MinimumSize)
copy(icmpHdr, h)
icmpHdr.SetType(header.ICMPv4EchoReply)
icmpHdr.SetChecksum(0)
icmpHdr.SetChecksum(^header.Checksum(icmpHdr, header.ChecksumVV(replyData, 0)))
dataVV := buffer.View(icmpHdr).ToVectorisedView()
dataVV.Append(replyData)
replyPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
ReserveHeaderBytes: int(r.MaxHeaderLength()),
Data: dataVV,
})
// Send out the reply packet.
sent := stats.ICMP.V4PacketsSent
if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
Protocol: header.ICMPv4ProtocolNumber,
TTL: r.DefaultTTL(),
TOS: stack.DefaultTOS,
}, replyPkt); err != nil {
sent.Dropped.Increment()
return
}
sent.EchoReply.Increment()
case header.ICMPv4EchoReply:
received.EchoReply.Increment()
e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt)
case header.ICMPv4DstUnreachable:
received.DstUnreachable.Increment()
pkt.Data.TrimFront(header.ICMPv4MinimumSize)
switch h.Code() {
case header.ICMPv4HostUnreachable:
e.handleControl(stack.ControlNoRoute, 0, pkt)
case header.ICMPv4PortUnreachable:
e.handleControl(stack.ControlPortUnreachable, 0, pkt)
case header.ICMPv4FragmentationNeeded:
mtu := uint32(h.MTU())
e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), pkt)
}
case header.ICMPv4SrcQuench:
received.SrcQuench.Increment()
case header.ICMPv4Redirect:
received.Redirect.Increment()
case header.ICMPv4TimeExceeded:
received.TimeExceeded.Increment()
case header.ICMPv4ParamProblem:
received.ParamProblem.Increment()
case header.ICMPv4Timestamp:
received.Timestamp.Increment()
case header.ICMPv4TimestampReply:
received.TimestampReply.Increment()
case header.ICMPv4InfoRequest:
received.InfoRequest.Increment()
case header.ICMPv4InfoReply:
received.InfoReply.Increment()
default:
received.Invalid.Increment()
}
}
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