Extract ICMP error sender from UDP

Store transport protocol number on packet buffers for use in ICMP error
generation.

Updates #2211.

PiperOrigin-RevId: 333252762

1 files changed, 46 insertions, 4 deletions

diff --git a/pkg/tcpip/header/icmpv4.go b/pkg/tcpip/header/icmpv4.go
index be03fb086..c00bcadfb 100644
--- a/pkg/tcpip/header/icmpv4.go
+++ b/pkg/tcpip/header/icmpv4.go
@@ -31,6 +31,27 @@ const (
 	// ICMPv4MinimumSize is the minimum size of a valid ICMP packet.
 	ICMPv4MinimumSize = 8
 
+	// ICMPv4MinimumErrorPayloadSize Is the smallest number of bytes of an
+	// errant packet's transport layer that an ICMP error type packet should
+	// attempt to send as per RFC 792 (see each type) and RFC 1122
+	// section 3.2.2 which states:
+	//      Every ICMP error message includes the Internet header and at
+	//      least the first 8 data octets of the datagram that triggered
+	//      the error; more than 8 octets MAY be sent; this header and data
+	//      MUST be unchanged from the received datagram.
+	//
+	// RFC 792 shows:
+	//   0                   1                   2                   3
+	//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	// |     Type      |     Code      |          Checksum             |
+	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	// |                             unused                            |
+	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	// |      Internet Header + 64 bits of Original Data Datagram      |
+	// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+	ICMPv4MinimumErrorPayloadSize = 8
+
 	// ICMPv4ProtocolNumber is the ICMP transport protocol number.
 	ICMPv4ProtocolNumber tcpip.TransportProtocolNumber = 1
 
@@ -39,15 +60,19 @@ const (
 	icmpv4ChecksumOffset = 2
 
 	// icmpv4MTUOffset is the offset of the MTU field
-	// in a ICMPv4FragmentationNeeded message.
+	// in an ICMPv4FragmentationNeeded message.
 	icmpv4MTUOffset = 6
 
 	// icmpv4IdentOffset is the offset of the ident field
-	// in a ICMPv4EchoRequest/Reply message.
+	// in an ICMPv4EchoRequest/Reply message.
 	icmpv4IdentOffset = 4
 
+	// icmpv4PointerOffset is the offset of the pointer field
+	// in an ICMPv4ParamProblem message.
+	icmpv4PointerOffset = 4
+
 	// icmpv4SequenceOffset is the offset of the sequence field
-	// in a ICMPv4EchoRequest/Reply message.
+	// in an ICMPv4EchoRequest/Reply message.
 	icmpv4SequenceOffset = 6
 )
 
@@ -72,15 +97,23 @@ const (
 	ICMPv4InfoReply      ICMPv4Type = 16
 )
 
+// ICMP codes for ICMPv4 Time Exceeded messages as defined in RFC 792.
+const (
+	ICMPv4TTLExceeded ICMPv4Code = 0
+)
+
 // ICMP codes for ICMPv4 Destination Unreachable messages as defined in RFC 792.
 const (
-	ICMPv4TTLExceeded         ICMPv4Code = 0
+	ICMPv4NetUnreachable      ICMPv4Code = 0
 	ICMPv4HostUnreachable     ICMPv4Code = 1
 	ICMPv4ProtoUnreachable    ICMPv4Code = 2
 	ICMPv4PortUnreachable     ICMPv4Code = 3
 	ICMPv4FragmentationNeeded ICMPv4Code = 4
 )
 
+// ICMPv4UnusedCode is a code to use in ICMP messages where no code is needed.
+const ICMPv4UnusedCode ICMPv4Code = 0
+
 // Type is the ICMP type field.
 func (b ICMPv4) Type() ICMPv4Type { return ICMPv4Type(b[0]) }
 
@@ -93,6 +126,15 @@ func (b ICMPv4) Code() ICMPv4Code { return ICMPv4Code(b[1]) }
 // SetCode sets the ICMP code field.
 func (b ICMPv4) SetCode(c ICMPv4Code) { b[1] = byte(c) }
 
+// SetPointer sets the pointer field in a Parameter error packet.
+// This is the first byte of the type specific data field.
+func (b ICMPv4) SetPointer(c byte) { b[icmpv4PointerOffset] = c }
+
+// SetTypeSpecific sets the full 32 bit type specific data field.
+func (b ICMPv4) SetTypeSpecific(val uint32) {
+	binary.BigEndian.PutUint32(b[icmpv4PointerOffset:], val)
+}
+
 // Checksum is the ICMP checksum field.
 func (b ICMPv4) Checksum() uint16 {
 	return binary.BigEndian.Uint16(b[icmpv4ChecksumOffset:])