Lollipop patch for Android source that does a check for Ethernet and then skips replacing network if found. Allows for eth0 and wlan0 to be active at same time.

lollipop_multiple_interface_CM.patch

diff -ur A/frameworks/base/services/core/java/com/android/server/ConnectivityService.java B/frameworks/base/services/core/java/com/android/server/ConnectivityService.java
--- A/frameworks/base/services/core/java/com/android/server/ConnectivityService.java	2015-09-01 12:55:15.000000000 -0500
+++ B/frameworks/base/services/core/java/com/android/server/ConnectivityService.java	2015-09-01 13:06:55.000000000 -0500
@@ -3915,6 +3915,7 @@
         if (!newNetwork.created) loge("ERROR: uncreated network being rematched.");
         if (nascent && !newNetwork.validated) loge("ERROR: nascent network not validated.");
         boolean keep = newNetwork.isVPN();
+        boolean keep_ethernet = newNetwork.isETHERNET();
         boolean isNewDefault = false;
         if (DBG) log("rematching " + newNetwork.name());
         // Find and migrate to this Network any NetworkRequests for
@@ -3950,54 +3951,57 @@
                             (currentNetwork != null ? currentNetwork.getCurrentScore() : 0) +
                             ", newScore = " + newNetwork.getCurrentScore());
                 }
-                if (currentNetwork == null ||
-                        currentNetwork.getCurrentScore() < newNetwork.getCurrentScore()) {
-                    if (currentNetwork != null) {
-                        if (DBG) log("   accepting network in place of " + currentNetwork.name());
-                        currentNetwork.networkRequests.remove(nri.request.requestId);
-                        currentNetwork.networkLingered.add(nri.request);
-                        affectedNetworks.add(currentNetwork);
-                    } else {
-                        if (DBG) log("   accepting network in place of null");
-                    }
-                    mNetworkForRequestId.put(nri.request.requestId, newNetwork);
-                    newNetwork.addRequest(nri.request);
-                    if (nri.isRequest && nri.request.legacyType != TYPE_NONE) {
-                        mLegacyTypeTracker.add(nri.request.legacyType, newNetwork);
-                    }
-                    keep = true;
-                    // Tell NetworkFactories about the new score, so they can stop
-                    // trying to connect if they know they cannot match it.
-                    // TODO - this could get expensive if we have alot of requests for this
-                    // network.  Think about if there is a way to reduce this.  Push
-                    // netid->request mapping to each factory?
-                    sendUpdatedScoreToFactories(nri.request, newNetwork.getCurrentScore());
-                    if (mDefaultRequest.requestId == nri.request.requestId) {
-                        isNewDefault = true;
-                        // TODO: Remove following line.  It's redundant with makeDefault call.
-                        mActiveDefaultNetwork = newNetwork.networkInfo.getType();
-                        if (newNetwork.linkProperties != null) {
-                            updateTcpBufferSizes(newNetwork);
-                            setDefaultDnsSystemProperties(
-                                    newNetwork.linkProperties.getDnsServers());
+                if (!keep_ethernet) {
+                    log("[NH] Ethernet should not get past here");
+                    if (currentNetwork == null ||
+                            currentNetwork.getCurrentScore() < newNetwork.getCurrentScore()) {
+                        if (currentNetwork != null) {
+                            if (DBG) log("   accepting network in place of " + currentNetwork.name());
+                            currentNetwork.networkRequests.remove(nri.request.requestId);
+                            currentNetwork.networkLingered.add(nri.request);
+                            affectedNetworks.add(currentNetwork);
                         } else {
-                            setDefaultDnsSystemProperties(new ArrayList<InetAddress>());
+                            if (DBG) log("   accepting network in place of null");
                         }
-                        // Maintain the illusion: since the legacy API only
-                        // understands one network at a time, we must pretend
-                        // that the current default network disconnected before
-                        // the new one connected.
-                        if (currentNetwork != null) {
-                            mLegacyTypeTracker.remove(currentNetwork.networkInfo.getType(),
-                                                      currentNetwork);
+                        mNetworkForRequestId.put(nri.request.requestId, newNetwork);
+                        newNetwork.addRequest(nri.request);
+                        if (nri.isRequest && nri.request.legacyType != TYPE_NONE) {
+                            mLegacyTypeTracker.add(nri.request.legacyType, newNetwork);
+                        }
+                        keep = true;
+                        // Tell NetworkFactories about the new score, so they can stop
+                        // trying to connect if they know they cannot match it.
+                        // TODO - this could get expensive if we have alot of requests for this
+                        // network.  Think about if there is a way to reduce this.  Push
+                        // netid->request mapping to each factory?
+                        sendUpdatedScoreToFactories(nri.request, newNetwork.getCurrentScore());
+                        if (mDefaultRequest.requestId == nri.request.requestId) {
+                            isNewDefault = true;
+                            // TODO: Remove following line.  It's redundant with makeDefault call.
+                            mActiveDefaultNetwork = newNetwork.networkInfo.getType();
+                            if (newNetwork.linkProperties != null) {
+                                updateTcpBufferSizes(newNetwork);
+                                setDefaultDnsSystemProperties(
+                                        newNetwork.linkProperties.getDnsServers());
+                            } else {
+                                setDefaultDnsSystemProperties(new ArrayList<InetAddress>());
+                            }
+                            // Maintain the illusion: since the legacy API only
+                            // understands one network at a time, we must pretend
+                            // that the current default network disconnected before
+                            // the new one connected.
+                            if (currentNetwork != null) {
+                                mLegacyTypeTracker.remove(currentNetwork.networkInfo.getType(),
+                                                          currentNetwork);
+                            }
+                            mDefaultInetConditionPublished = newNetwork.validated ? 100 : 0;
+                            mLegacyTypeTracker.add(newNetwork.networkInfo.getType(), newNetwork);
+                            notifyLockdownVpn(newNetwork);
+                            }
                         }
-                        mDefaultInetConditionPublished = newNetwork.validated ? 100 : 0;
-                        mLegacyTypeTracker.add(newNetwork.networkInfo.getType(), newNetwork);
-                        notifyLockdownVpn(newNetwork);
                     }
                 }
             }
-        }
         // Linger any networks that are no longer needed.
         for (NetworkAgentInfo nai : affectedNetworks) {
             boolean teardown = !nai.isVPN() && nai.validated;
diff -ur A/frameworks/base/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java B/frameworks/base/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java
--- A/frameworks/base/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java	2015-09-01 12:59:00.000000000 -0500
+++ B/frameworks/base/services/core/java/com/android/server/connectivity/NetworkAgentInfo.java	2015-09-01 13:01:37.000000000 -0500
@@ -125,6 +125,11 @@
         return networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_VPN);
     }
 
+    // Add Ethernet check
+    public boolean isETHERNET() {
+        return networkCapabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET);
+    }
+    
     // Get the current score for this Network.  This may be modified from what the
     // NetworkAgent sent, as it has modifiers applied to it.
     public int getCurrentScore() {

I've been working on getting both interfaces working and I need to test this patch on a clean Android build.