Allow binding a socket to a specific QNetworkInterface

For now, via a private API.

Provide a new socket engine option - BindInterfaceIndex, and use it if
a valid interface is passed to QAbstractSocketPrivate::bind().

Note that this feature is not fully functional on macOS:
both SO_BINDTODEVICE and IP{V6}_BOUND_IF only work for limiting
outgoing datagrams. The patch uses IP{V6}_BOUND_IF, because it allows
to avoid number -> string -> number conversion.
As of now, extra filtering of incoming data should be done on the user
side.

Task-number: QTBUG-80704
Task-number: QTBUG-139697
Pick-to: 6.10 6.8
Change-Id: Ic207908313d9d25f96c23ecc363181ff0ae8232a
Reviewed-by: Thiago Macieira <[email protected]>
Reviewed-by: Mårten Nordheim <[email protected]>

4 files changed, 93 insertions, 4 deletions

diff --git a/src/network/socket/qabstractsocket.cpp b/src/network/socket/qabstractsocket.cpp
index ce3626304c8..f2474ad7e97 100644
--- a/src/network/socket/qabstractsocket.cpp
+++ b/src/network/socket/qabstractsocket.cpp
@@ -432,6 +432,7 @@
 
 #include "qabstractsocket.h"
 #include "qabstractsocket_p.h"
+#include "qnetworkinterface.h"
 
 #include "private/qhostinfo_p.h"
 
@@ -1505,8 +1506,6 @@ bool QAbstractSocketPrivate::bind(const QHostAddress &address, quint16 port, QAb
 {
     Q_Q(QAbstractSocket);
 
-    Q_UNUSED(iface); // will be used in a follow-up patch
-
     // now check if the socket engine is initialized and to the right type
     if (!socketEngine || !socketEngine->isValid()) {
         QHostAddress nullAddress;
@@ -1538,6 +1537,10 @@ bool QAbstractSocketPrivate::bind(const QHostAddress &address, quint16 port, QAb
         socketEngine->setOption(QAbstractSocketEngine::BindExclusively, 0);
 #endif
     }
+#if QT_CONFIG(networkinterface)
+    if (iface && iface->isValid())
+        socketEngine->setOption(QAbstractSocketEngine::BindInterfaceIndex, iface->index());
+#endif
     bool result = socketEngine->bind(address, port);
     cachedSocketDescriptor = socketEngine->socketDescriptor();
 
diff --git a/src/network/socket/qabstractsocketengine_p.h b/src/network/socket/qabstractsocketengine_p.h
index b9cdf38b5e0..48ebfed71a2 100644
--- a/src/network/socket/qabstractsocketengine_p.h
+++ b/src/network/socket/qabstractsocketengine_p.h
@@ -75,7 +75,8 @@ public:
         ReceivePacketInformation,
         ReceiveHopLimit,
         MaxStreamsSocketOption,
-        PathMtuInformation
+        PathMtuInformation,
+        BindInterfaceIndex,
     };
 
     enum PacketHeaderOption {
diff --git a/src/network/socket/qnativesocketengine_unix.cpp b/src/network/socket/qnativesocketengine_unix.cpp
index a9bc2d92b44..b5fbb5c2e00 100644
--- a/src/network/socket/qnativesocketengine_unix.cpp
+++ b/src/network/socket/qnativesocketengine_unix.cpp
@@ -11,6 +11,7 @@
 #include "qhostaddress.h"
 #include "qvarlengtharray.h"
 #include "qnetworkinterface.h"
+#include "qnetworkinterface_p.h"
 #include "qendian.h"
 #ifdef Q_OS_WASM
 #include <private/qeventdispatcher_wasm_p.h>
@@ -82,6 +83,9 @@ static void convertToLevelAndOption(QNativeSocketEngine::SocketOption opt,
     case QNativeSocketEngine::MaxStreamsSocketOption:
         Q_UNREACHABLE();
 
+    case QNativeSocketEngine::BindInterfaceIndex:
+        Q_UNREACHABLE(); // handled directly in setOption()
+
     case QNativeSocketEngine::BroadcastSocketOption:
         n = SO_BROADCAST;
         break;
@@ -373,7 +377,27 @@ bool QNativeSocketEnginePrivate::setOption(QNativeSocketEngine::SocketOption opt
 #endif
         return false;
     }
-
+    case QNativeSocketEngine::BindInterfaceIndex: {
+#if defined(SO_BINDTOIFINDEX) // seen on Linux
+        return ::setsockopt(socketDescriptor, SOL_SOCKET, SO_BINDTOIFINDEX,
+                            &v, sizeof(v)) == 0;
+#elif defined(IPV6_BOUND_IF) && defined(IP_BOUND_IF) // seen on Darwin
+        // note: on Darwin, this only limits sending the data, not receiving it
+        if (socketProtocol == QAbstractSocket::IPv6Protocol
+            || socketProtocol == QAbstractSocket::AnyIPProtocol) {
+            return ::setsockopt(socketDescriptor, IPPROTO_IPV6, IPV6_BOUND_IF, &v, sizeof(v)) == 0;
+        } else {
+            return ::setsockopt(socketDescriptor, IPPROTO_IP, IP_BOUND_IF, &v, sizeof(v)) == 0;
+        }
+#elif defined(SO_BINDTODEVICE) && QT_CONFIG(networkinterface)
+        // need to convert to interface name
+        const QByteArray name = QNetworkInterfaceManager::interfaceNameFromIndex(v).toLatin1();
+        return ::setsockopt(socketDescriptor, SOL_SOCKET, SO_BINDTODEVICE,
+                            name.data(), socklen_t(name.size())) == 0;
+#else
+        return false;
+#endif
+    }
     default:
         break;
     }
diff --git a/src/network/socket/qnativesocketengine_win.cpp b/src/network/socket/qnativesocketengine_win.cpp
index 9933ea06745..598467ef629 100644
--- a/src/network/socket/qnativesocketengine_win.cpp
+++ b/src/network/socket/qnativesocketengine_win.cpp
@@ -153,6 +153,9 @@ static void convertToLevelAndOption(QNativeSocketEngine::SocketOption opt,
     case QNativeSocketEngine::MaxStreamsSocketOption:
         Q_UNREACHABLE();
 
+    case QNativeSocketEngine::BindInterfaceIndex:
+        Q_UNREACHABLE(); // handled directly in setOption()
+
     case QNativeSocketEngine::ReceiveBufferSocketOption:
         n = SO_RCVBUF;
         break;
@@ -441,6 +444,64 @@ bool QNativeSocketEnginePrivate::setOption(QNativeSocketEngine::SocketOption opt
         return true;
     }
 
+    case QNativeSocketEngine::BindInterfaceIndex: {
+        int ret = 0;
+        if (socketProtocol == QAbstractSocket::IPv6Protocol
+            || socketProtocol == QAbstractSocket::AnyIPProtocol) {
+            // IPv6 - uses host byte order
+            // Bind outgoing datagrams to the interface
+            if (!ret) {
+                ret = ::setsockopt(socketDescriptor, IPPROTO_IPV6, IPV6_UNICAST_IF,
+                                   reinterpret_cast<char *>(&v), sizeof(v));
+            }
+            if (!ret) {
+                ret = ::setsockopt(socketDescriptor, IPPROTO_IPV6, IPV6_MULTICAST_IF,
+                                   reinterpret_cast<char *>(&v), sizeof(v));
+            }
+            // Bind incoming datagrams to the interface
+            if (!ret) {
+                const int enable = 1;
+                ret = ::setsockopt(socketDescriptor, IPPROTO_IPV6, IPV6_IFLIST,
+                                   reinterpret_cast<const char *>(&enable), sizeof(enable));
+                if (!ret) {
+                    ret = ::setsockopt(socketDescriptor, IPPROTO_IPV6, IPV6_ADD_IFLIST,
+                                       reinterpret_cast<char *>(&v), sizeof(v));
+                }
+            }
+        }
+        bool result = !ret;
+        if (result) {
+            // Try to set the IPv4 options unconditionally, but ignore
+            // the result if the protocol is not IPv4-only
+
+            // IPv4 - uses network byte order
+            int netIdx = htonl(v);
+            // Bind outgoing datagrams to the interface
+            if (!ret) {
+                ret = ::setsockopt(socketDescriptor, IPPROTO_IP, IP_UNICAST_IF,
+                                   reinterpret_cast<char *>(&netIdx), sizeof(netIdx));
+            }
+            if (!ret) {
+                ret = ::setsockopt(socketDescriptor, IPPROTO_IP, IP_MULTICAST_IF,
+                                   reinterpret_cast<char *>(&netIdx), sizeof(netIdx));
+            }
+            // Bind incoming datagrams to the interface
+            if (!ret) {
+                const int enable = 1;
+                ret = ::setsockopt(socketDescriptor, IPPROTO_IP, IP_IFLIST,
+                                   reinterpret_cast<const char *>(&enable), sizeof(enable));
+                if (!ret) {
+                    // uses host byte order here
+                    ret = ::setsockopt(socketDescriptor, IPPROTO_IP, IP_ADD_IFLIST,
+                                       reinterpret_cast<char *>(&v), sizeof(v));
+                }
+            }
+            if (socketProtocol == QAbstractSocket::IPv4Protocol)
+                result = !ret;
+        }
+        return result;
+    }
+
     default:
         break;
     }