/// <summary>
/// Attempts to parse the given value into a <see cref="HostName"/>. Returns
/// true if successful.
/// </summary>
public static bool TryParse(string value, out HostName hostName)
{
try
{
hostName = new HostName(value);
return(true);
}
catch (ArgumentNullException)
{
hostName = null;
return(false);
}
catch (FormatException)
{
hostName = null;
return(false);
}
}
private bool SeenServer(HostName whoisServer, int depth)
{
// Referral limit
if (depth > 255)
{
return(true);
}
// Ignore top level request
if (depth == 0)
{
return(Referrer?.SeenServer(whoisServer, 1) ?? false);
}
if (WhoisServer.IsEqualTo(whoisServer))
{
return(true);
}
return(Referrer != null && Referrer.SeenServer(whoisServer, depth + 1));
}
/// <summary>
/// Performs a WHOIS lookup for the given request.
/// </summary>
public async Task <WhoisResponse> LookupAsync(WhoisRequest request)
{
if (string.IsNullOrEmpty(request.Query))
{
throw new ArgumentNullException("domain");
}
// Trim leading '.'
if (request.Query.StartsWith("."))
{
request.Query = request.Query.Substring(1);
}
// Validate domain name
if (HostName.TryParse(request.Query, out var hostName) == false)
{
throw new WhoisException($"WHOIS Query Format Error: {request.Query}");
}
Log.Debug("Looking up WHOIS response for: {0}", hostName.Value);
// Set our starting point
WhoisResponse response;
if (string.IsNullOrEmpty(request.WhoisServerUrl))
{
// Lookup root WHOIS server for the TLD
response = await ServerLookup.LookupAsync(request);
}
else
{
// Use the given WHOIS server
response = WhoisResponse.WithServerUrl(request.WhoisServerUrl);
}
// Main loop: download & parse WHOIS data and follow the referrer chain
var whoisServerUrl = response?.WhoisServerUrl;
while (string.IsNullOrEmpty(whoisServerUrl) == false && !hostName.IsTld)
{
// Download
var content = await Download(whoisServerUrl, request);
// Parse result
var parsed = whoisParser.Parse(whoisServerUrl, content);
// Build referrer chain
response = response.Chain(parsed);
// Check for referral loop
if (request.FollowReferrer == false)
{
break;
}
if (response.SeenServer(response.WhoisServerUrl))
{
break;
}
// Lookup result in referral server
whoisServerUrl = response.WhoisServerUrl;
}
return(response);
}
/// <summary>
/// Performs a WHOIS lookup for the given request.
/// </summary>
public async Task <WhoisResponse> LookupAsync(WhoisRequest request)
{
if (string.IsNullOrEmpty(request.Query))
{
throw new ArgumentNullException($"{nameof(request)}.{nameof(request.Query)}");
}
// Trim leading '.'
if (request.Query.StartsWith("."))
{
request.Query = request.Query.Substring(1);
}
// Validate domain name
if (HostName.TryParse(request.Query, out var hostName) == false)
{
throw new WhoisException($"WHOIS Query Format Error: {request.Query}");
}
Log.Debug("Looking up WHOIS response for: {0}", hostName.Value);
// Set our starting point
WhoisResponse response;
if (string.IsNullOrEmpty(request.WhoisServer))
{
// Lookup root WHOIS server for the TLD
response = await ServerLookup.LookupAsync(request);
}
else
{
// Use the given WHOIS server
response = WhoisResponse.WithServerUrl(request.WhoisServer);
}
// If query is for a top level domain, we're finished
if (hostName.IsTld)
{
return(response);
}
// Main loop: download & parse WHOIS data and follow the referrer chain
var whoisServer = response?.WhoisServer;
while (whoisServer != null)
{
// Download
var content = await Download(whoisServer.Value, request);
// Parse result
var parsed = Parser.Parse(whoisServer.Value, content);
// Sanity check: ensure the last response has some data
if (parsed.FieldsParsed == 0 && response.FieldsParsed > 0)
{
break;
}
// Build referrer chain
response = response.Chain(parsed);
// Check for referral loop
if (request.FollowReferrer == false)
{
break;
}
if (response.SeenServer(response.WhoisServer))
{
break;
}
// Lookup result in referral server
whoisServer = response.WhoisServer;
}
return(response);
}
/// <summary>
/// Determines if the given WHOIS server URL has been visited in this lookup chain
/// </summary>
internal bool SeenServer(HostName whoisServer)
{
return(SeenServer(whoisServer, 0));
}