Merge "Use IPv6 hop limit from upstream interface."

am: 53f6d1b060

Change-Id: I827f0ad4c60f7fcc0b470b597ebaacfc0fc7dac7

services/net/java/android/net/ip/IpServer.java

@@ -430,6 +430,8 @@ public class IpServer extends StateMachine {
             params.mtu = v6only.getMtu();
             params.hasDefaultRoute = v6only.hasIPv6DefaultRoute();
 
+            if (params.hasDefaultRoute) params.hopLimit = getHopLimit(v6only.getInterfaceName());
+
             for (LinkAddress linkAddr : v6only.getLinkAddresses()) {
                 if (linkAddr.getPrefixLength() != RFC7421_PREFIX_LENGTH) continue;
 
@@ -549,6 +551,20 @@ public class IpServer extends StateMachine {
         }
     }
 
+    private byte getHopLimit(String upstreamIface) {
+        try {
+            int upstreamHopLimit = Integer.parseUnsignedInt(
+                    mNetd.getProcSysNet(INetd.IPV6, INetd.CONF, upstreamIface, "hop_limit"));
+            // Add one hop to account for this forwarding device
+            upstreamHopLimit++;
+            // Cap the hop limit to 255.
+            return (byte) Integer.min(upstreamHopLimit, 255);
+        } catch (Exception e) {
+            mLog.e("Failed to find upstream interface hop limit", e);
+        }
+        return RaParams.DEFAULT_HOPLIMIT;
+    }
+
     private void setRaParams(RaParams newParams) {
         if (mRaDaemon != null) {
             final RaParams deprecatedParams =