QNetConMonitor(Win): Account for LOCALNETWORK reachability

What I originally thought NLM_CONNECTIVITY_IPV*_SUBNET meant turns out
to be what NLM_CONNECTIVITY_IPV*_LOCALNETWORK is, leaving me to wonder
when *_SUBNET is actually used. Anyway we now also check *_LOCALNETWORK
to make sure we're not unnecessarily denying certain connections to be
made.

At the same time check for link-local connections where both local and
remote are link-local, in this case even NLM_CONNECTIVITY_IPV*_NOTRAFFIC
is valid. Unfortunately this check cannot be done in
QNetworkStatusMonitor, so QNAM will likely not allow these connections.

Task-number: QTBUG-80947
Change-Id: Ieb96ce9f4a478eef0c3ea47f2471f701c102b4d4
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

1 files changed, 31 insertions, 7 deletions

diff --git a/src/network/kernel/qnetconmonitor_win.cpp b/src/network/kernel/qnetconmonitor_win.cpp
index 1566e7f914..59b6cd5b66 100644
--- a/src/network/kernel/qnetconmonitor_win.cpp
+++ b/src/network/kernel/qnetconmonitor_win.cpp
@@ -163,11 +163,14 @@ private:
     ComPtr<QNetworkConnectionEvents> connectionEvents;
     // We can assume we have access to internet/subnet when this class is created because
     // connection has already been established to the peer:
-    NLM_CONNECTIVITY connectivity =
-            NLM_CONNECTIVITY(NLM_CONNECTIVITY_IPV4_INTERNET | NLM_CONNECTIVITY_IPV6_INTERNET
-                             | NLM_CONNECTIVITY_IPV4_SUBNET | NLM_CONNECTIVITY_IPV6_SUBNET);
+    NLM_CONNECTIVITY connectivity = NLM_CONNECTIVITY(
+            NLM_CONNECTIVITY_IPV4_INTERNET | NLM_CONNECTIVITY_IPV6_INTERNET
+            | NLM_CONNECTIVITY_IPV4_SUBNET | NLM_CONNECTIVITY_IPV6_SUBNET
+            | NLM_CONNECTIVITY_IPV4_LOCALNETWORK | NLM_CONNECTIVITY_IPV6_LOCALNETWORK
+            | NLM_CONNECTIVITY_IPV4_NOTRAFFIC | NLM_CONNECTIVITY_IPV6_NOTRAFFIC);
 
     bool sameSubnet = false;
+    bool isLinkLocal = false;
     bool monitoring = false;
     bool comInitFailed = false;
     bool remoteIsIPv6 = false;
@@ -370,6 +373,7 @@ bool QNetworkConnectionMonitorPrivate::setTargets(const QHostAddress &local,
         return false;
     }
     sameSubnet = remote.isInSubnet(local, it->prefixLength());
+    isLinkLocal = remote.isLinkLocal() && local.isLinkLocal();
     remoteIsIPv6 = remote.protocol() == QAbstractSocket::IPv6Protocol;
 
     return connectionEvents->setTarget(iface);
@@ -461,9 +465,28 @@ void QNetworkConnectionMonitor::stopMonitoring()
 bool QNetworkConnectionMonitor::isReachable()
 {
     Q_D(QNetworkConnectionMonitor);
-    NLM_CONNECTIVITY required = d->sameSubnet
-            ? (d->remoteIsIPv6 ? NLM_CONNECTIVITY_IPV6_SUBNET : NLM_CONNECTIVITY_IPV4_SUBNET)
-            : (d->remoteIsIPv6 ? NLM_CONNECTIVITY_IPV6_INTERNET : NLM_CONNECTIVITY_IPV4_INTERNET);
+
+    const NLM_CONNECTIVITY RequiredSameSubnetIPv6 =
+            NLM_CONNECTIVITY(NLM_CONNECTIVITY_IPV6_SUBNET | NLM_CONNECTIVITY_IPV6_LOCALNETWORK
+                             | NLM_CONNECTIVITY_IPV6_INTERNET);
+    const NLM_CONNECTIVITY RequiredSameSubnetIPv4 =
+            NLM_CONNECTIVITY(NLM_CONNECTIVITY_IPV4_SUBNET | NLM_CONNECTIVITY_IPV4_LOCALNETWORK
+                             | NLM_CONNECTIVITY_IPV4_INTERNET);
+
+    NLM_CONNECTIVITY required;
+    if (d->isLinkLocal) {
+        required = NLM_CONNECTIVITY(
+                d->remoteIsIPv6 ? NLM_CONNECTIVITY_IPV6_NOTRAFFIC | RequiredSameSubnetIPv6
+                                : NLM_CONNECTIVITY_IPV4_NOTRAFFIC | RequiredSameSubnetIPv4);
+    } else if (d->sameSubnet) {
+        required =
+                NLM_CONNECTIVITY(d->remoteIsIPv6 ? RequiredSameSubnetIPv6 : RequiredSameSubnetIPv4);
+
+    } else {
+        required = NLM_CONNECTIVITY(d->remoteIsIPv6 ? NLM_CONNECTIVITY_IPV6_INTERNET
+                                                    : NLM_CONNECTIVITY_IPV4_INTERNET);
+    }
+
     return d_func()->connectivity & required;
 }
 
@@ -695,7 +718,8 @@ bool QNetworkStatusMonitor::isNetworkAccessible()
 {
     return d_func()->connectivity
             & (NLM_CONNECTIVITY_IPV4_INTERNET | NLM_CONNECTIVITY_IPV6_INTERNET
-               | NLM_CONNECTIVITY_IPV4_SUBNET | NLM_CONNECTIVITY_IPV6_SUBNET);
+               | NLM_CONNECTIVITY_IPV4_SUBNET | NLM_CONNECTIVITY_IPV6_SUBNET
+               | NLM_CONNECTIVITY_IPV4_LOCALNETWORK | NLM_CONNECTIVITY_IPV6_LOCALNETWORK);
 }
 
 bool QNetworkStatusMonitor::isEnabled()