IPv6: Path MTU Discovery

* Copied and adapted IPv4 error handling code for IPv6 (to handle
  ICMP6_PACKET_TOO_BIG)

Change-Id: Id14cf6221626b5c723fbe77f19aa0d6b9d25f36a
Reviewed-on: https://review.haiku-os.org/c/haiku/+/10170
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>

src/add-ons/kernel/network/protocols/icmp6/icmp6.cpp

@@ -39,6 +39,24 @@ static net_stack_module_info *sStackModule;
 static net_ndp_module_info *sIPv6NDPModule;
 
 
+static net_error
+icmp6_to_net_error(uint8 type, uint8 code)
+{
+	switch (type) {
+		case ICMP6_PARAM_PROB:
+			return B_NET_ERROR_PARAMETER_PROBLEM;
+
+		case ICMP6_PACKET_TOO_BIG:
+			return B_NET_ERROR_MESSAGE_SIZE;
+
+		default:
+			break;
+	}
+
+	return (net_error)0;
+}
+
+
 net_protocol *
 icmp6_init_protocol(net_socket *socket)
 {
@@ -280,6 +298,38 @@ icmp6_receive_data(net_buffer *buffer)
 			}
 		}
 
+		case ICMP6_DST_UNREACH:
+		case ICMP6_PACKET_TOO_BIG:
+		case ICMP6_TIME_EXCEEDED:
+		case ICMP6_PARAM_PROB:
+		{
+			net_domain* domain = get_domain(buffer);
+			if (domain == NULL)
+				break;
+
+			net_error error = icmp6_to_net_error(header.icmp6_type,
+				header.icmp6_code);
+			if (error == 0)
+				break;
+
+			net_error_data dataStorage = {};
+			net_error_data* data = NULL;
+			if (error == B_NET_ERROR_MESSAGE_SIZE) {
+				data = &dataStorage;
+				data->mtu = ntohl(header.icmp6_mtu);
+
+				// IPv6 minimum fragment size is 1280 bytes, so if the "next MTU"
+				// is smaller than that, we can be sure it's invalid.
+				if (data->mtu < 1280)
+					data = NULL;
+			}
+
+			// Deliver the error to the domain protocol which will
+			// propagate the error to the upper protocols
+			bufferHeader.Remove();
+			return domain->module->error_received(error, data, buffer);
+		}
+
 		default:
 			// unrecognized messages go to neighbor discovery protocol handler
 			return sIPv6NDPModule->receive_data(buffer);

src/add-ons/kernel/network/protocols/ipv6/ipv6.cpp

@@ -45,9 +45,11 @@
 	#define TRACE_SK(protocol, format, args...) \
 		dprintf("IPv6 [%" B_PRIdBIGTIME "] %p " format "\n", system_time(), \
 			protocol, ##args)
+	#define TRACE_ONLY(x) x
 #else
 	#define TRACE(args...)
 	#define TRACE_SK(args...)
+	#define TRACE_ONLY(x)
 #endif
 
 
@@ -1579,9 +1581,56 @@ ipv6_deliver_data(net_protocol* _protocol, net_buffer* buffer)
 
 
 status_t
-ipv6_error_received(net_error error, net_error_data* errorData, net_buffer* data)
+ipv6_error_received(net_error error, net_error_data* errorData, net_buffer* buffer)
 {
-	return B_ERROR;
+	TRACE("  ipv6_error_received(error %d, buffer %p [%" B_PRIu32 " bytes])",
+		(int)error, buffer, buffer->size);
+
+	NetBufferHeaderReader<IPv6Header> bufferHeader(buffer);
+	if (bufferHeader.Status() != B_OK)
+		return bufferHeader.Status();
+
+	IPv6Header& header = bufferHeader.Data();
+	TRACE_ONLY(dump_ipv6_header(header));
+
+	// We do not check the packet length, as we usually only get a part of it
+	if (header.ProtocolVersion() != IPV6_VERSION)
+		return B_BAD_DATA;
+
+	// Restore addresses of the original buffer
+
+	// lower layers notion of broadcast or multicast have no relevance to us
+	// TODO: they actually have when deciding whether to send an ICMP error
+	buffer->msg_flags &= ~(MSG_BCAST | MSG_MCAST);
+
+	fill_sockaddr_in6((struct sockaddr_in6*)buffer->source, header.Src());
+	fill_sockaddr_in6((struct sockaddr_in6*)buffer->destination,
+		header.Dst());
+
+	// test if the packet is really from us
+	if (!sDatalinkModule->is_local_address(sDomain, buffer->source, NULL,
+			NULL)) {
+		TRACE("  ipv6_error_received(): packet was not for us");
+		return B_ERROR;
+	}
+
+	if (error == B_NET_ERROR_MESSAGE_SIZE) {
+		if (errorData != NULL)
+			errorData->mtu -= sizeof(IPv6Header);
+	} else if (error == B_NET_ERROR_REDIRECT_HOST) {
+		// TODO: Update the routing table!
+	}
+
+	buffer->protocol = header.NextHeader();
+
+	bufferHeader.Remove(sizeof(IPv6Header));
+
+	net_protocol_module_info* protocol = receiving_protocol(buffer->protocol);
+	if (protocol == NULL)
+		return B_ERROR;
+
+	// propagate error
+	return protocol->error_received(error, errorData, buffer);
 }