error_t nbnsSendQuery(DnsCacheEntry *entry)
{
error_t error;
size_t length;
size_t offset;
NetBuffer *buffer;
NbnsHeader *message;
DnsQuestion *dnsQuestion;
IpAddr destIpAddr;
//Allocate a memory buffer to hold the NBNS query message
buffer = udpAllocBuffer(DNS_MESSAGE_MAX_SIZE, &offset);
//Failed to allocate buffer?
if(!buffer) return ERROR_OUT_OF_MEMORY;
//Point to the NBNS header
message = netBufferAt(buffer, offset);
//Format NBNS query message
message->id = htons(entry->id);
message->qr = 0;
message->opcode = DNS_OPCODE_QUERY;
message->aa = 0;
message->tc = 0;
message->rd = 0;
message->ra = 0;
message->z = 0;
message->b = 1;
message->rcode = DNS_RCODE_NO_ERROR;
//The NBNS query contains one question
message->qdcount = HTONS(1);
message->ancount = 0;
message->nscount = 0;
message->arcount = 0;
//Length of the NBNS query message
length = sizeof(DnsHeader);
//Encode the NetBIOS name
length += nbnsEncodeName(entry->name, message->questions);
//Point to the corresponding question structure
dnsQuestion = DNS_GET_QUESTION(message, length);
//Fill in question structure
dnsQuestion->qtype = HTONS(DNS_RR_TYPE_NB);
dnsQuestion->qclass = HTONS(DNS_RR_CLASS_IN);
//Update the length of the NBNS query message
length += sizeof(DnsQuestion);
//Adjust the length of the multi-part buffer
netBufferSetLength(buffer, offset + length);
//Debug message
TRACE_INFO("Sending NBNS message (%" PRIuSIZE " bytes)...\r\n", length);
//Dump message
dnsDumpMessage((DnsHeader *) message, length);
//The destination address is the broadcast address
destIpAddr.length = sizeof(Ipv4Addr);
ipv4GetBroadcastAddr(entry->interface, &destIpAddr.ipv4Addr);
//A request packet is always sent to the well known port 137
error = udpSendDatagramEx(entry->interface, NBNS_PORT,
&destIpAddr, NBNS_PORT, buffer, offset, IPV4_DEFAULT_TTL);
//Free previously allocated memory
netBufferFree(buffer);
//Return status code
return error;
}
error_t nbnsSendResponse(NetInterface *interface,
const IpAddr *destIpAddr, uint16_t destPort, uint16_t id)
{
error_t error;
size_t length;
size_t offset;
ChunkedBuffer *buffer;
NbnsHeader *message;
NbnsAddrEntry *addrEntry;
DnsResourceRecord *resourceRecord;
//Allocate a memory buffer to hold the NBNS response message
buffer = udpAllocBuffer(DNS_MESSAGE_MAX_SIZE, &offset);
//Failed to allocate buffer?
if(!buffer) return ERROR_OUT_OF_MEMORY;
//Point to the NBNS header
message = chunkedBufferAt(buffer, offset);
//Take the identifier from the query message
message->id = id;
//Format NBNS response header
message->qr = 1;
message->opcode = DNS_OPCODE_QUERY;
message->aa = 1;
message->tc = 0;
message->rd = 1;
message->ra = 1;
message->z = 0;
message->b = 0;
message->rcode = DNS_RCODE_NO_ERROR;
//The NBNS response contains 1 answer resource record
message->qdcount = 0;
message->ancount = HTONS(1);
message->nscount = 0;
message->arcount = 0;
//NBNS response message length
length = sizeof(DnsHeader);
//Encode the host name using the NBNS name notation
length += nbnsEncodeName(interface->hostname, (uint8_t *) message + length);
//Point to the corresponding resource record
resourceRecord = DNS_GET_RESOURCE_RECORD(message, length);
//Fill in resource record
resourceRecord->rtype = HTONS(DNS_RR_TYPE_NB);
resourceRecord->rclass = HTONS(DNS_RR_CLASS_IN);
resourceRecord->ttl = HTONL(NBNS_DEFAULT_RESOURCE_RECORD_TTL);
resourceRecord->rdlength = HTONS(sizeof(NbnsAddrEntry));
//Point to the address entry array
addrEntry = (NbnsAddrEntry *) resourceRecord->rdata;
//Fill in address entry
addrEntry->flags = HTONS(NBNS_G_UNIQUE | NBNS_ONT_BNODE);
addrEntry->addr = interface->ipv4Config.addr;
//Update the length of the NBNS response message
length += sizeof(DnsResourceRecord) + sizeof(NbnsAddrEntry);
//Adjust the length of the multi-part buffer
chunkedBufferSetLength(buffer, offset + length);
//Debug message
TRACE_INFO("Sending NBNS message (%" PRIuSIZE " bytes)...\r\n", length);
//Dump message
dnsDumpMessage((DnsHeader *) message, length);
//A response packet is always sent to the source UDP port and
//source IP address of the request packet
error = udpSendDatagramEx(interface, NBNS_PORT, destIpAddr,
destPort, buffer, offset, IPV4_DEFAULT_TTL);
//Free previously allocated memory
chunkedBufferFree(buffer);
//Return status code
return error;
}