error_t nbnsResolve(NetInterface *interface, const char_t *name, IpAddr *ipAddr)
{
error_t error;
DnsCacheEntry *entry;
#if (NET_RTOS_SUPPORT == ENABLED)
systime_t delay;
//Debug message
TRACE_INFO("Resolving host name %s (NBNS resolver)...\r\n", name);
#endif
//Acquire exclusive access to the DNS cache
osAcquireMutex(&dnsCacheMutex);
//Search the DNS cache for the specified host name
entry = dnsFindEntry(interface, name, HOST_TYPE_IPV4, HOST_NAME_RESOLVER_NBNS);
//Check whether a matching entry has been found
if(entry)
{
//Host name already resolved?
if(entry->state == DNS_STATE_RESOLVED ||
entry->state == DNS_STATE_PERMANENT)
{
//Return the corresponding IP address
*ipAddr = entry->ipAddr;
//Successful host name resolution
error = NO_ERROR;
}
else
{
//Host name resolution is in progress...
error = ERROR_IN_PROGRESS;
}
}
else
{
//If no entry exists, then create a new one
entry = dnsCreateEntry();
//Record the host name whose IP address is unknown
strcpy(entry->name, name);
//Initialize DNS cache entry
entry->type = HOST_TYPE_IPV4;
entry->protocol = HOST_NAME_RESOLVER_NBNS;
entry->interface = interface;
//Initialize retransmission counter
entry->retransmitCount = NBNS_CLIENT_MAX_RETRIES;
//Send NBNS query
error = nbnsSendQuery(entry);
//NBNS message successfully sent?
if(!error)
{
//Save the time at which the query message was sent
entry->timestamp = osGetSystemTime();
//Set timeout value
entry->timeout = NBNS_CLIENT_INIT_TIMEOUT;
entry->maxTimeout = NBNS_CLIENT_MAX_TIMEOUT;
//Decrement retransmission counter
entry->retransmitCount--;
//Switch state
entry->state = DNS_STATE_IN_PROGRESS;
//Host name resolution is in progress
error = ERROR_IN_PROGRESS;
}
}
//Release exclusive access to the DNS cache
osReleaseMutex(&dnsCacheMutex);
#if (NET_RTOS_SUPPORT == ENABLED)
//Set default polling interval
delay = DNS_CACHE_INIT_POLLING_INTERVAL;
//Wait the host name resolution to complete
while(error == ERROR_IN_PROGRESS)
{
//Wait until the next polling period
osDelayTask(delay);
//Acquire exclusive access to the DNS cache
osAcquireMutex(&dnsCacheMutex);
//Search the DNS cache for the specified host name
entry = dnsFindEntry(interface, name, HOST_TYPE_IPV4, HOST_NAME_RESOLVER_NBNS);
//Check whether a matching entry has been found
if(entry)
{
//Host name successfully resolved?
if(entry->state == DNS_STATE_RESOLVED)
{
//Return the corresponding IP address
*ipAddr = entry->ipAddr;
//Successful host name resolution
error = NO_ERROR;
}
}
else
{
//Host name resolution failed
error = ERROR_FAILURE;
}
//Release exclusive access to the DNS cache
osReleaseMutex(&dnsCacheMutex);
//Backoff support for less aggressive polling
delay = MIN(delay * 2, DNS_CACHE_MAX_POLLING_INTERVAL);
}
//Check status code
if(error)
{
//Failed to resolve host name
TRACE_INFO("Host name resolution failed!\r\n");
}
else
{
//Successful host name resolution
TRACE_INFO("Host name resolved to %s...\r\n", ipAddrToString(ipAddr, NULL));
}
#endif
//Return status code
return error;
}
error_t dnsResolve(NetInterface *interface,
const char_t *name, HostType type, IpAddr *ipAddr)
{
error_t error;
systime_t delay;
DnsCacheEntry *entry;
//Debug message
TRACE_INFO("Resolving host name %s (DNS resolver)...\r\n", name);
//Acquire exclusive access to the DNS cache
osMutexAcquire(dnsCacheMutex);
//Search the DNS cache for the specified host name
entry = dnsFindEntry(interface, name, type, HOST_NAME_RESOLVER_DNS);
//Check whether a matching entry has been found
if(entry)
{
//Host name already resolved?
if(entry->state == DNS_STATE_RESOLVED ||
entry->state == DNS_STATE_PERMANENT)
{
//Return the corresponding IP address
*ipAddr = entry->ipAddr;
//Successful host name resolution
error = NO_ERROR;
}
else
{
//Host name resolution is in progress...
error = ERROR_IN_PROGRESS;
}
}
else
{
//If no entry exists, then create a new one
entry = dnsCreateEntry();
//Record the host name whose IP address is unknown
strcpy(entry->name, name);
//Initialize DNS cache entry
entry->type = type;
entry->protocol = HOST_NAME_RESOLVER_DNS;
entry->interface = interface;
//Select primary DNS server
entry->dnsServerNum = 0;
//Get an ephemeral port number
entry->port = socketGetEphemeralPort();
//An identifier is used by the DNS client to match replies
//with corresponding requests
entry->id = tcpIpStackGetRand();
//Callback function to be called when a DNS response is received
error = udpAttachRxCallback(interface, entry->port, dnsProcessResponse, NULL);
//Check status code
if(!error)
{
//Initialize retransmission counter
entry->retransmitCount = DNS_CLIENT_MAX_RETRIES;
//Send DNS query
error = dnsSendQuery(entry);
//DNS message successfully sent?
if(!error)
{
//Save the time at which the query message was sent
entry->timestamp = osGetTickCount();
//Set timeout value
entry->timeout = DNS_CLIENT_INIT_TIMEOUT;
entry->maxTimeout = DNS_CLIENT_MAX_TIMEOUT;
//Decrement retransmission counter
entry->retransmitCount--;
//Switch state
entry->state = DNS_STATE_IN_PROGRESS;
//Host name resolution is in progress
error = ERROR_IN_PROGRESS;
}
else
{
//Unregister callback function
udpDetachRxCallback(interface, entry->port);
}
}
}
//Release exclusive access to the DNS cache
osMutexRelease(dnsCacheMutex);
//Set default polling interval
delay = DNS_CACHE_INIT_POLLING_INTERVAL;
//Wait the host name resolution to complete
while(error == ERROR_IN_PROGRESS)
{
//Wait until the next polling period
osDelay(delay);
//Acquire exclusive access to the DNS cache
osMutexAcquire(dnsCacheMutex);
//Search the DNS cache for the specified host name
entry = dnsFindEntry(interface, name, type, HOST_NAME_RESOLVER_DNS);
//Check whether a matching entry has been found
if(entry)
{
//Host name successfully resolved?
if(entry->state == DNS_STATE_RESOLVED)
{
//Return the corresponding IP address
*ipAddr = entry->ipAddr;
//Successful host name resolution
error = NO_ERROR;
}
}
else
{
//Host name resolution failed
error = ERROR_FAILURE;
}
//Release exclusive access to the DNS cache
osMutexRelease(dnsCacheMutex);
//Backoff support for less aggressive polling
delay = min(delay * 2, DNS_CACHE_MAX_POLLING_INTERVAL);
}
//Check status code
if(error)
{
//Failed to resolve host name
TRACE_INFO("Host name resolution failed!\r\n");
}
else
{
//Successful host name resolution
TRACE_INFO("Host name resolved to %s...\r\n", ipAddrToString(ipAddr, NULL));
}
//Return status code
return error;
}
