void nbnsProcessQuery(NetInterface *interface, const Ipv4PseudoHeader *pseudoHeader,
const UdpHeader *udpHeader, const NbnsHeader *message, size_t length)
{
size_t pos;
DnsQuestion *question;
//The NBNS query shall contain one question
if(ntohs(message->qdcount) != 1)
return;
//Parse NetBIOS name
pos = nbnsParseName(message, length, sizeof(DnsHeader), NULL);
//Invalid name?
if(!pos)
return;
//Malformed mDNS message?
if((pos + sizeof(DnsQuestion)) > length)
return;
//Point to the corresponding entry
question = DNS_GET_QUESTION(message, pos);
//Check the class and the type of the request
if(ntohs(question->qclass) != DNS_RR_CLASS_IN)
return;
if(ntohs(question->qtype) != DNS_RR_TYPE_NB)
return;
//Compare NetBIOS names
if(nbnsCompareName(message, length, sizeof(DnsHeader), interface->hostname))
{
uint16_t destPort;
IpAddr destIpAddr;
//A response packet is always sent to the source UDP port and
//source IP address of the request packet
destIpAddr.length = sizeof(Ipv4Addr);
destIpAddr.ipv4Addr = pseudoHeader->srcAddr;
//Convert the port number to host byte order
destPort = ntohs(udpHeader->srcPort);
//Send NBNS response
nbnsSendResponse(interface, &destIpAddr, destPort, message->id);
}
}
void nbnsProcessResponse(NetInterface *interface, const Ipv4PseudoHeader *pseudoHeader,
const UdpHeader *udpHeader, const NbnsHeader *message, size_t length)
{
uint_t i;
size_t pos;
DnsCacheEntry *entry;
DnsResourceRecord *resourceRecord;
NbnsAddrEntry *addrEntry;
//The NBNS response shall contain one answer
if(ntohs(message->qdcount) != 0 && ntohs(message->ancount) != 1)
return;
//Parse NetBIOS name
pos = nbnsParseName(message, length, sizeof(DnsHeader), NULL);
//Invalid name?
if(!pos) return;
//Point to the associated resource record
resourceRecord = DNS_GET_RESOURCE_RECORD(message, pos);
//Point to the resource data
pos += sizeof(DnsResourceRecord);
//Make sure the resource record is valid
if(pos > length)
return;
if((pos + ntohs(resourceRecord->rdlength)) > length)
return;
//Check the class and the type of the resource record
if(ntohs(resourceRecord->rclass) != DNS_RR_CLASS_IN)
return;
if(ntohs(resourceRecord->rtype) != DNS_RR_TYPE_NB)
return;
//Verify the length of the data field
if(ntohs(resourceRecord->rdlength) < sizeof(NbnsAddrEntry))
return;
//Acquire exclusive access to the DNS cache
osAcquireMutex(&dnsCacheMutex);
//Loop through DNS cache entries
for(i = 0; i < DNS_CACHE_SIZE; i++)
{
//Point to the current entry
entry = &dnsCache[i];
//NBNS name resolution in progress?
if(entry->state == DNS_STATE_IN_PROGRESS &&
entry->protocol == HOST_NAME_RESOLVER_NBNS &&
entry->type == HOST_TYPE_IPV4)
{
//Compare identifiers
if(entry->id == ntohs(message->id))
{
//Compare NetBIOS names
if(nbnsCompareName(message, length, sizeof(DnsHeader), entry->name))
{
//Point to the address entry array
addrEntry = (NbnsAddrEntry *) resourceRecord->rdata;
//Copy the IPv4 address
entry->ipAddr.length = sizeof(Ipv4Addr);
entry->ipAddr.ipv4Addr = addrEntry->addr;
//Save current time
entry->timestamp = osGetSystemTime();
//Save TTL value
entry->timeout = ntohl(resourceRecord->ttl) * 1000;
//Limit the lifetime of the NBNS cache entries
entry->timeout = MIN(entry->timeout, NBNS_MAX_LIFETIME);
//Host name successfully resolved
entry->state = DNS_STATE_RESOLVED;
}
}
}
}
//Release exclusive access to the DNS cache
osReleaseMutex(&dnsCacheMutex);
}