Use the ICMP error response facility

Add code in IPv6 to send ICMP packets while processing extension headers.

Add some accounting in processing IPV6 Extension headers which
allows us to report meaningful information back in ICMP parameter
problem packets.

IPv4 also needs to send a message when an unsupported protocol
is requested.

Add some tests to generate both ipv4 and ipv6 packets with
various errors and check the responses.

Add some new checkers and cleanup some inconsistencies in
the messages in that file.

Add new error types for the ICMPv4/6 generators.

Fix a bug in the ICMPv4 generator that stopped it from generating
"Unknown protocol" messages.

Updates #2211

PiperOrigin-RevId: 334661716

1 files changed, 13 insertions, 3 deletions

diff --git a/pkg/tcpip/header/icmpv6.go b/pkg/tcpip/header/icmpv6.go
index 4eb5abd79..6be31beeb 100644
--- a/pkg/tcpip/header/icmpv6.go
+++ b/pkg/tcpip/header/icmpv6.go
@@ -156,9 +156,14 @@ const (
 
 // ICMP codes used with Parameter Problem (Type 4). As per RFC 4443 section 3.4.
 const (
+	// ICMPv6ErroneousHeader indicates an erroneous header field was encountered.
 	ICMPv6ErroneousHeader ICMPv6Code = 0
-	ICMPv6UnknownHeader   ICMPv6Code = 1
-	ICMPv6UnknownOption   ICMPv6Code = 2
+
+	// ICMPv6UnknownHeader indicates an unrecognized Next Header type encountered.
+	ICMPv6UnknownHeader ICMPv6Code = 1
+
+	// ICMPv6UnknownOption indicates an unrecognized IPv6 option was encountered.
+	ICMPv6UnknownOption ICMPv6Code = 2
 )
 
 // ICMPv6UnusedCode is the code value used with ICMPv6 messages which don't use
@@ -177,7 +182,12 @@ func (b ICMPv6) Code() ICMPv6Code { return ICMPv6Code(b[1]) }
 // SetCode sets the ICMP code field.
 func (b ICMPv6) SetCode(c ICMPv6Code) { b[1] = byte(c) }
 
-// SetTypeSpecific sets the full 32 bit type specific data field.
+// TypeSpecific returns the type specific data field.
+func (b ICMPv6) TypeSpecific() uint32 {
+	return binary.BigEndian.Uint32(b[icmpv6PointerOffset:])
+}
+
+// SetTypeSpecific sets the type specific data field.
 func (b ICMPv6) SetTypeSpecific(val uint32) {
 	binary.BigEndian.PutUint32(b[icmpv6PointerOffset:], val)
 }