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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 udp contains the implementation of the UDP transport protocol. To use
// it in the networking stack, this package must be added to the project, and
// activated on the stack by passing udp.NewProtocol() as one of the
// transport protocols when calling stack.New(). Then endpoints can be created
// by passing udp.ProtocolNumber as the transport protocol number when calling
// Stack.NewEndpoint().
package udp
import (
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/buffer"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"gvisor.dev/gvisor/pkg/tcpip/transport/raw"
"gvisor.dev/gvisor/pkg/waiter"
)
const (
// ProtocolNumber is the udp protocol number.
ProtocolNumber = header.UDPProtocolNumber
)
type protocol struct{}
// Number returns the udp protocol number.
func (*protocol) Number() tcpip.TransportProtocolNumber {
return ProtocolNumber
}
// NewEndpoint creates a new udp endpoint.
func (*protocol) NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
return newEndpoint(stack, netProto, waiterQueue), nil
}
// NewRawEndpoint creates a new raw UDP endpoint. It implements
// stack.TransportProtocol.NewRawEndpoint.
func (p *protocol) NewRawEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
return raw.NewEndpoint(stack, netProto, header.UDPProtocolNumber, waiterQueue)
}
// MinimumPacketSize returns the minimum valid udp packet size.
func (*protocol) MinimumPacketSize() int {
return header.UDPMinimumSize
}
// ParsePorts returns the source and destination ports stored in the given udp
// packet.
func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
h := header.UDP(v)
return h.SourcePort(), h.DestinationPort(), nil
}
// HandleUnknownDestinationPacket handles packets targeted at this protocol but
// that don't match any existing endpoint.
func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, pkt tcpip.PacketBuffer) bool {
// Get the header then trim it from the view.
hdr := header.UDP(pkt.Data.First())
if int(hdr.Length()) > pkt.Data.Size() {
// Malformed packet.
r.Stack().Stats().UDP.MalformedPacketsReceived.Increment()
return true
}
// TODO(b/129426613): only send an ICMP message if UDP checksum is valid.
// Only send ICMP error if the address is not a multicast/broadcast
// v4/v6 address or the source is not the unspecified address.
//
// See: point e) in https://tools.ietf.org/html/rfc4443#section-2.4
if id.LocalAddress == header.IPv4Broadcast || header.IsV4MulticastAddress(id.LocalAddress) || header.IsV6MulticastAddress(id.LocalAddress) || id.RemoteAddress == header.IPv6Any || id.RemoteAddress == header.IPv4Any {
return true
}
// As per RFC: 1122 Section 3.2.2.1 A host SHOULD generate Destination
// Unreachable messages with code:
//
// 2 (Protocol Unreachable), when the designated transport protocol
// is not supported; or
//
// 3 (Port Unreachable), when the designated transport protocol
// (e.g., UDP) is unable to demultiplex the datagram but has no
// protocol mechanism to inform the sender.
switch len(id.LocalAddress) {
case header.IPv4AddressSize:
if !r.Stack().AllowICMPMessage() {
r.Stack().Stats().ICMP.V4PacketsSent.RateLimited.Increment()
return true
}
// As per RFC 1812 Section 4.3.2.3
//
// ICMP datagram SHOULD contain as much of the original
// datagram as possible without the length of the ICMP
// datagram exceeding 576 bytes
//
// NOTE: The above RFC referenced is different from the original
// recommendation in RFC 1122 where it mentioned that at least 8
// bytes of the payload must be included. Today linux and other
// systems implement the] RFC1812 definition and not the original
// RFC 1122 requirement.
mtu := int(r.MTU())
if mtu > header.IPv4MinimumProcessableDatagramSize {
mtu = header.IPv4MinimumProcessableDatagramSize
}
headerLen := int(r.MaxHeaderLength()) + header.ICMPv4MinimumSize
available := int(mtu) - headerLen
payloadLen := len(pkt.NetworkHeader) + pkt.Data.Size()
if payloadLen > available {
payloadLen = available
}
// The buffers used by pkt may be used elsewhere in the system.
// For example, a raw or packet socket may use what UDP
// considers an unreachable destination. Thus we deep copy pkt
// to prevent multiple ownership and SR errors.
newNetHeader := append(buffer.View(nil), pkt.NetworkHeader...)
payload := newNetHeader.ToVectorisedView()
payload.Append(pkt.Data.ToView().ToVectorisedView())
payload.CapLength(payloadLen)
hdr := buffer.NewPrependable(headerLen)
pkt := header.ICMPv4(hdr.Prepend(header.ICMPv4MinimumSize))
pkt.SetType(header.ICMPv4DstUnreachable)
pkt.SetCode(header.ICMPv4PortUnreachable)
pkt.SetChecksum(header.ICMPv4Checksum(pkt, payload))
r.WritePacket(nil /* gso */, hdr, payload, stack.NetworkHeaderParams{Protocol: header.ICMPv4ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS})
case header.IPv6AddressSize:
if !r.Stack().AllowICMPMessage() {
r.Stack().Stats().ICMP.V6PacketsSent.RateLimited.Increment()
return true
}
// As per RFC 4443 section 2.4
//
// (c) Every ICMPv6 error message (type < 128) MUST include
// as much of the IPv6 offending (invoking) packet (the
// packet that caused the error) as possible without making
// the error message packet exceed the minimum IPv6 MTU
// [IPv6].
mtu := int(r.MTU())
if mtu > header.IPv6MinimumMTU {
mtu = header.IPv6MinimumMTU
}
headerLen := int(r.MaxHeaderLength()) + header.ICMPv6DstUnreachableMinimumSize
available := int(mtu) - headerLen
payloadLen := len(pkt.NetworkHeader) + pkt.Data.Size()
if payloadLen > available {
payloadLen = available
}
payload := buffer.NewVectorisedView(len(pkt.NetworkHeader), []buffer.View{pkt.NetworkHeader})
payload.Append(pkt.Data)
payload.CapLength(payloadLen)
hdr := buffer.NewPrependable(headerLen)
pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6DstUnreachableMinimumSize))
pkt.SetType(header.ICMPv6DstUnreachable)
pkt.SetCode(header.ICMPv6PortUnreachable)
pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, payload))
r.WritePacket(nil /* gso */, hdr, payload, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS})
}
return true
}
// SetOption implements TransportProtocol.SetOption.
func (p *protocol) SetOption(option interface{}) *tcpip.Error {
return tcpip.ErrUnknownProtocolOption
}
// Option implements TransportProtocol.Option.
func (p *protocol) Option(option interface{}) *tcpip.Error {
return tcpip.ErrUnknownProtocolOption
}
// NewProtocol returns a UDP transport protocol.
func NewProtocol() stack.TransportProtocol {
return &protocol{}
}
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