Make UDP traceroute work.

Adds support to generate Port Unreachable messages for UDP
datagrams received on a port for which there is no valid
endpoint.

Fixes #703

PiperOrigin-RevId: 267034418

2 files changed, 14 insertions, 16 deletions

diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 451d3880e..e1f622af6 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -15,7 +15,6 @@
 package icmp
 
 import (
-	"encoding/binary"
 	"sync"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -368,14 +367,13 @@ func send4(r *stack.Route, ident uint16, data buffer.View) *tcpip.Error {
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	// Set the ident to the user-specified port. Sequence number should
-	// already be set by the user.
-	binary.BigEndian.PutUint16(data[header.ICMPv4PayloadOffset:], ident)
-
 	hdr := buffer.NewPrependable(header.ICMPv4MinimumSize + int(r.MaxHeaderLength()))
 
 	icmpv4 := header.ICMPv4(hdr.Prepend(header.ICMPv4MinimumSize))
 	copy(icmpv4, data)
+	// Set the ident to the user-specified port. Sequence number should
+	// already be set by the user.
+	icmpv4.SetIdent(ident)
 	data = data[header.ICMPv4MinimumSize:]
 
 	// Linux performs these basic checks.
@@ -394,14 +392,13 @@ func send6(r *stack.Route, ident uint16, data buffer.View) *tcpip.Error {
 		return tcpip.ErrInvalidEndpointState
 	}
 
-	// Set the ident. Sequence number is provided by the user.
-	binary.BigEndian.PutUint16(data[header.ICMPv6MinimumSize:], ident)
-
-	hdr := buffer.NewPrependable(header.ICMPv6EchoMinimumSize + int(r.MaxHeaderLength()))
+	hdr := buffer.NewPrependable(header.ICMPv6MinimumSize + int(r.MaxHeaderLength()))
 
-	icmpv6 := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
+	icmpv6 := header.ICMPv6(hdr.Prepend(header.ICMPv6MinimumSize))
 	copy(icmpv6, data)
-	data = data[header.ICMPv6EchoMinimumSize:]
+	// Set the ident. Sequence number is provided by the user.
+	icmpv6.SetIdent(ident)
+	data = data[header.ICMPv6MinimumSize:]
 
 	if icmpv6.Type() != header.ICMPv6EchoRequest || icmpv6.Code() != 0 {
 		return tcpip.ErrInvalidEndpointState
diff --git a/pkg/tcpip/transport/icmp/protocol.go b/pkg/tcpip/transport/icmp/protocol.go
index 7fdba5d56..1eb790932 100644
--- a/pkg/tcpip/transport/icmp/protocol.go
+++ b/pkg/tcpip/transport/icmp/protocol.go
@@ -23,7 +23,6 @@
 package icmp
 
 import (
-	"encoding/binary"
 	"fmt"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -92,7 +91,7 @@ func (p *protocol) MinimumPacketSize() int {
 	case ProtocolNumber4:
 		return header.ICMPv4MinimumSize
 	case ProtocolNumber6:
-		return header.ICMPv6EchoMinimumSize
+		return header.ICMPv6MinimumSize
 	}
 	panic(fmt.Sprint("unknown protocol number: ", p.number))
 }
@@ -101,16 +100,18 @@ func (p *protocol) MinimumPacketSize() int {
 func (p *protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
 	switch p.number {
 	case ProtocolNumber4:
-		return 0, binary.BigEndian.Uint16(v[header.ICMPv4PayloadOffset:]), nil
+		hdr := header.ICMPv4(v)
+		return 0, hdr.Ident(), nil
 	case ProtocolNumber6:
-		return 0, binary.BigEndian.Uint16(v[header.ICMPv6MinimumSize:]), nil
+		hdr := header.ICMPv6(v)
+		return 0, hdr.Ident(), nil
 	}
 	panic(fmt.Sprint("unknown protocol number: ", p.number))
 }
 
 // HandleUnknownDestinationPacket handles packets targeted at this protocol but
 // that don't match any existing endpoint.
-func (p *protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, buffer.VectorisedView) bool {
+func (p *protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, buffer.View, buffer.VectorisedView) bool {
 	return true
 }