fix: dns rewrites and flush

client/platforms/linux/daemon/dnsutilslinux.cpp

@@ -7,9 +7,11 @@
 #include <net/if.h>
 
 #include <QDBusVariant>
+#include <QNetworkInterface>
 #include <QTimer>
 #include <QtDBus/QtDBus>
 
+#include "core/networkUtilities.h"
 #include "leakdetector.h"
 #include "logger.h"
 
@@ -64,6 +66,15 @@ DnsUtilsLinux::~DnsUtilsLinux() {
   MZ_COUNT_DTOR(DnsUtilsLinux);
 
   if (m_resolver) {
+    for (auto iterator = m_linkDefaultRoutes.constBegin();
+         iterator != m_linkDefaultRoutes.constEnd(); ++iterator) {
+      QList<QVariant> argumentList;
+      argumentList << QVariant::fromValue(iterator.key());
+      argumentList << QVariant::fromValue(iterator.value());
+      m_resolver->asyncCallWithArgumentList(QStringLiteral("SetLinkDefaultRoute"),
+                                            argumentList);
+    }
+
     for (auto iterator = m_linkDomains.constBegin();
          iterator != m_linkDomains.constEnd(); ++iterator) {
       QList<QVariant> argumentList;
@@ -82,6 +93,12 @@ DnsUtilsLinux::~DnsUtilsLinux() {
 
 bool DnsUtilsLinux::updateResolvers(const QString& ifname,
                                     const QList<QHostAddress>& resolvers) {
+  for (auto iterator = m_linkDefaultRoutes.constBegin();
+       iterator != m_linkDefaultRoutes.constEnd(); ++iterator) {
+    setLinkDefaultRoute(iterator.key(), iterator.value());
+  }
+  m_linkDefaultRoutes.clear();
+
   m_ifindex = if_nametoindex(qPrintable(ifname));
   if (m_ifindex <= 0) {
     logger.error() << "Unable to resolve ifindex for" << ifname;
@@ -96,9 +113,9 @@ bool DnsUtilsLinux::updateResolvers(const QString& ifname,
     return true;
   }
 
+  updateLinkDefaultRoutes();
   setLinkDNS(m_ifindex, resolvers);
   setLinkDefaultRoute(m_ifindex, true);
-  setLinkDomains(m_ifindex, {DnsLinkDomain(".", true)});
   updateLinkDomains();
   return true;
 }
@@ -107,6 +124,12 @@ bool DnsUtilsLinux::restoreResolvers() {
   m_pendingIfname.clear();
   m_pendingResolvers.clear();
 
+  for (auto iterator = m_linkDefaultRoutes.constBegin();
+       iterator != m_linkDefaultRoutes.constEnd(); ++iterator) {
+    setLinkDefaultRoute(iterator.key(), iterator.value());
+  }
+  m_linkDefaultRoutes.clear();
+
   for (auto iterator = m_linkDomains.constBegin();
        iterator != m_linkDomains.constEnd(); ++iterator) {
     setLinkDomains(iterator.key(), iterator.value());
@@ -132,7 +155,7 @@ bool DnsUtilsLinux::restoreResolvers() {
 void DnsUtilsLinux::dnsCallCompleted(QDBusPendingCallWatcher* call) {
   QDBusPendingReply<> reply = *call;
   if (reply.isError()) {
-    logger.debug() << "DBus call failed (may be transient after systemd-resolved restart)";
+    logger.error() << "Error received from the DBus service";
   }
   delete call;
 }
@@ -200,6 +223,23 @@ void DnsUtilsLinux::setLinkDefaultRoute(int ifindex, bool enable) {
                    SLOT(dnsCallCompleted(QDBusPendingCallWatcher*)));
 }
 
+void DnsUtilsLinux::updateLinkDefaultRoutes() {
+  const QNetworkInterface defaultIface = NetworkUtilities::getGatewayAndIface().second;
+  const int ifindex = defaultIface.index();
+  if (ifindex <= 0) {
+    logger.warning() << "Unable to determine default route interface";
+    return;
+  }
+  if ((ifindex == m_ifindex) || m_linkDefaultRoutes.contains(ifindex)) {
+    return;
+  }
+
+  // Gateway link normally has DefaultRoute=yes. Keep behavior simple:
+  // disable it while VPN DNS is active and restore to yes on teardown.
+  m_linkDefaultRoutes[ifindex] = true;
+  setLinkDefaultRoute(ifindex, false);
+}
+
 void DnsUtilsLinux::updateLinkDomains() {
   if (!m_resolver) return;
   /* Get the list of search domains, and remove any others that might conspire

client/platforms/linux/daemon/dnsutilslinux.h

@@ -31,6 +31,7 @@ class DnsUtilsLinux final : public DnsUtils {
   void setLinkDNS(int ifindex, const QList<QHostAddress>& resolvers);
   void setLinkDomains(int ifindex, const QList<DnsLinkDomain>& domains);
   void setLinkDefaultRoute(int ifindex, bool enable);
+  void updateLinkDefaultRoutes();
   void updateLinkDomains();
 
  private slots:
@@ -43,6 +44,7 @@ class DnsUtilsLinux final : public DnsUtils {
   int m_ifindex = 0;
   int m_domainRetries = 0;
   QMap<int, DnsLinkDomainList> m_linkDomains;
+  QMap<int, bool> m_linkDefaultRoutes;
   QScopedPointer<QDBusInterface> m_resolver;
   QString m_pendingIfname;
   QList<QHostAddress> m_pendingResolvers;

service/server/router_linux.cpp

@@ -167,22 +167,27 @@ bool RouterLinux::flushDns()
 
     //check what the dns manager use
     if (isServiceActive("nscd.service")) {
-        qDebug() << "Restarting nscd.service";
-        p.start("systemctl", { "restart", "nscd" });
+        qDebug() << "Flushing nscd cache";
+        p.start("nscd", { "--invalidate=hosts" });
     } else if (isServiceActive("systemd-resolved.service")) {
-        qDebug() << "Restarting systemd-resolved.service";
-        p.start("systemctl", { "restart", "systemd-resolved" });
+        qDebug() << "Flushing systemd-resolved DNS cache";
+        p.start("resolvectl", { "flush-caches" });
     } else {
         qDebug() << "No suitable DNS manager found.";
         return false;
     }
 
     p.waitForFinished();
-    QByteArray output(p.readAll());
+    QByteArray output = p.readAll();
+    if ((p.exitStatus() != QProcess::NormalExit) || (p.exitCode() != 0)) {
+        qDebug().noquote() << "Failed to flush DNS: " + output;
+        return false;
+    }
+
     if (output.isEmpty())
         qDebug().noquote() << "Flush dns completed";
     else
-        qDebug().noquote() << "OUTPUT systemctl restart nscd/systemd-resolved: " + output;
+        qDebug().noquote() << "OUTPUT dns flush: " + output;
 
     return true;
 }