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Client: Add SRV-based virtual hosting support #2930

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merged 2 commits into from
Nov 15, 2022
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Client: Add SRV-based virtual hosting support #2930

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24adc20
Internal: Refactor NetworkUtil::ParseNetworkAddress
hoffie Oct 19, 2022
ed18ad6
Client: Add SRV-based virtual hosting support
hoffie Oct 19, 2022
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4 changes: 4 additions & 0 deletions src/client.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -477,7 +477,11 @@ void CClient::StartDelayTimer()
bool CClient::SetServerAddr ( QString strNAddr )
{
CHostAddress HostAddress;
#ifdef CLIENT_NO_SRV_CONNECT
if ( NetworkUtil().ParseNetworkAddress ( strNAddr, HostAddress, bEnableIPv6 ) )
#else
if ( NetworkUtil().ParseNetworkAddressWithSrvDiscovery ( strNAddr, HostAddress, bEnableIPv6 ) )
#endif
{
// apply address to the channel
Channel.SetAddress ( HostAddress );
Expand Down
120 changes: 95 additions & 25 deletions src/util.cpp
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Expand Up @@ -889,6 +889,100 @@ QSize CMinimumStackedLayout::sizeHint() const
* Other Classes *
\******************************************************************************/
// Network utility functions ---------------------------------------------------
bool NetworkUtil::ParseNetworkAddressString ( QString strAddress, QHostAddress& InetAddr, bool bEnableIPv6 )
{
// try to get host by name, assuming
// that the string contains a valid host name string or IP address
const QHostInfo HostInfo = QHostInfo::fromName ( strAddress );

if ( HostInfo.error() != QHostInfo::NoError )
{
// qInfo() << qUtf8Printable ( QString ( "Invalid hostname" ) );
return false; // invalid address
}

foreach ( const QHostAddress HostAddr, HostInfo.addresses() )
{
// qInfo() << qUtf8Printable ( QString ( "Resolved network address to %1 for proto %2" ) .arg ( HostAddr.toString() ) .arg (
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// HostAddr.protocol() ) );
if ( HostAddr.protocol() == QAbstractSocket::IPv4Protocol || ( bEnableIPv6 && HostAddr.protocol() == QAbstractSocket::IPv6Protocol ) )
{
InetAddr = HostAddr;
return true;
}
}
return false;
}

#ifndef CLIENT_NO_SRV_CONNECT
bool NetworkUtil::ParseNetworkAddressSrv ( QString strAddress, CHostAddress& HostAddress, bool bEnableIPv6 )
{
// init requested host address with invalid address first
HostAddress = CHostAddress();

QRegularExpression plainHostRegex ( "^([^\\[:0-9.][^:]*)$" );
if ( plainHostRegex.match ( strAddress ).capturedStart() != 0 )
{
// not a plain hostname? then don't attempt SRV lookup and fail
// immediately.
return false;
}

QDnsLookup* dns = new QDnsLookup();
dns->setType ( QDnsLookup::SRV );
dns->setName ( QString ( "_jamulus._udp.%1" ).arg ( strAddress ) );
dns->lookup();
// QDnsLookup::lookup() works asynchronously. Therefore, wait for
// it to complete here by resuming the main loop here.
// This is not nice and blocks the UI, but is similar to what
// the regular resolve function does as well.
QTime dieTime = QTime::currentTime().addMSecs ( DNS_SRV_RESOLVE_TIMEOUT_MS );
while ( QTime::currentTime() < dieTime && !dns->isFinished() )
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Not a fan of busy waiting (even if it's limited). Isn't there any blocking function or something like a signal?

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@pljones pljones Nov 12, 2022 •
edited
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You're asking for a Qt equivalent of AA/AAAA lookup for SRV names? (I'd guess all the Qt AA/AAAA lookup does is something very like this.)

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Isn't there any blocking function

The existing code path uses QHostInfo::fromName, which is a blocking function. I haven't found any equivalent for SRV lookups.

or something like a signal?

The QDnsLookup, which I've used here, is supposed to be used via signals. However, this requires -- as far as I can see -- an inversion of the control flow as the existing logic relies on blocking. Even when that refactoring is done, new questions come up: How should the UI behave? Currently it blocks. If it continues to stay responsive during lookup, we would need some other kind of indicator, so that's kind of a rabbit hole. Not saying that it shouldn't be done, but rather that it's a larger refactoring which I didn't want to do as part of this PR.

In short: That's the best and least intrusive way I've found. If someone finds a better way, I'm certainly open to it. :)

{
QCoreApplication::processEvents ( QEventLoop::ExcludeUserInputEvents, 100 );
}
QList<QDnsServiceRecord> records = dns->serviceRecords();
dns->deleteLater();
if ( records.length() != 1 )
{
return false;
}
QDnsServiceRecord record = records.first();
if ( record.target() == "." || record.target() == "" )
{
// RFC2782 says that "." indicates that the service is not available.
// Qt strips the trailing dot, which is why we check for empty string
// as well. Therefore, the "." part might be redundant, but this would
// need further testing to confirm.
// End processing here (= return true), but pass back an
// invalid HostAddress to let the connect logic fail properly.
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HostAddress = CHostAddress ( QHostAddress ( "." ), 0 );
return true;
}
qDebug() << qUtf8Printable (
QString ( "resolved %1 to a single SRV record: %2:%3" ).arg ( strAddress ).arg ( record.target() ).arg ( record.port() ) );

QHostAddress InetAddr;
if ( ParseNetworkAddressString ( record.target(), InetAddr, bEnableIPv6 ) )
{
HostAddress = CHostAddress ( InetAddr, record.port() );
return true;
}
return false;
}

bool NetworkUtil::ParseNetworkAddressWithSrvDiscovery ( QString strAddress, CHostAddress& HostAddress, bool bEnableIPv6 )
{
// Try SRV-based discovery first:
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Trying SRV first is the saner behavior. It comes at the cost that everyone has to do the SRV lookup and wait for the (possibly empty) reply.

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Agreed. The DNS server should fail fairly fast if the entry isn't there. At worst it should double the lookup time.

if ( ParseNetworkAddressSrv ( strAddress, HostAddress, bEnableIPv6 ) )
{
return true;
}
// Try regular connect via plain IP or host name lookup (A/AAAA):
return ParseNetworkAddress ( strAddress, HostAddress, bEnableIPv6 );
}
#endif

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bool NetworkUtil::ParseNetworkAddress ( QString strAddress, CHostAddress& HostAddress, bool bEnableIPv6 )
{
QHostAddress InetAddr;
Expand Down Expand Up @@ -970,31 +1064,7 @@ bool NetworkUtil::ParseNetworkAddress ( QString strAddress, CHostAddress& HostAd
return false; // invalid address
}

// try to get host by name, assuming
// that the string contains a valid host name string
const QHostInfo HostInfo = QHostInfo::fromName ( strAddress );

if ( HostInfo.error() != QHostInfo::NoError )
{
// qInfo() << qUtf8Printable ( QString ( "Invalid hostname" ) );
return false; // invalid address
}

bool bFoundAddr = false;

foreach ( const QHostAddress HostAddr, HostInfo.addresses() )
{
// qInfo() << qUtf8Printable ( QString ( "Resolved network address to %1 for proto %2" ) .arg ( HostAddr.toString() ) .arg (
// HostAddr.protocol() ) );
if ( HostAddr.protocol() == QAbstractSocket::IPv4Protocol || ( bEnableIPv6 && HostAddr.protocol() == QAbstractSocket::IPv6Protocol ) )
{
InetAddr = HostAddr;
bFoundAddr = true;
break;
}
}

if ( !bFoundAddr )
if ( !ParseNetworkAddressString ( strAddress, InetAddr, bEnableIPv6 ) )
{
// no valid address found
// qInfo() << qUtf8Printable ( QString ( "No IP address found for hostname" ) );
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14 changes: 12 additions & 2 deletions src/util.h
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Expand Up @@ -53,6 +53,9 @@
#include <QElapsedTimer>
#include <QTextBoundaryFinder>
#include <QTimer>
#ifndef CLIENT_NO_SRV_CONNECT
# include <QDnsLookup>
#endif
#ifndef _WIN32
# include <QThread>
#endif
Expand All @@ -79,8 +82,9 @@ class CClient; // forward declaration of CClient
#endif

/* Definitions ****************************************************************/
#define METER_FLY_BACK 2
#define INVALID_MIDI_CH -1 // invalid MIDI channel definition
#define METER_FLY_BACK 2
#define INVALID_MIDI_CH -1 // invalid MIDI channel definition
#define DNS_SRV_RESOLVE_TIMEOUT_MS 500

/* Global functions ***********************************************************/
// converting float to short
Expand Down Expand Up @@ -1038,6 +1042,12 @@ class CNetworkTransportProps
class NetworkUtil
{
public:
static bool ParseNetworkAddressString ( QString strAddress, QHostAddress& InetAddr, bool bEnableIPv6 );

#ifndef CLIENT_NO_SRV_CONNECT
static bool ParseNetworkAddressSrv ( QString strAddress, CHostAddress& HostAddress, bool bEnableIPv6 );
static bool ParseNetworkAddressWithSrvDiscovery ( QString strAddress, CHostAddress& HostAddress, bool bEnableIPv6 );
#endif
static bool ParseNetworkAddress ( QString strAddress, CHostAddress& HostAddress, bool bEnableIPv6 );

static QString FixAddress ( const QString& strAddress );
Expand Down