Merge "Reduce advertised ipv6 mtu by 16 to fit ethernet header"
diff --git a/Tethering/src/android/net/ip/IpServer.java b/Tethering/src/android/net/ip/IpServer.java
index b4d49c0..8116057 100644
--- a/Tethering/src/android/net/ip/IpServer.java
+++ b/Tethering/src/android/net/ip/IpServer.java
@@ -610,7 +610,12 @@
if (v6only != null) {
params = new RaParams();
- params.mtu = v6only.getMtu();
+ // We advertise an mtu lower by 16, which is the closest multiple of 8 >= 14,
+ // the ethernet header size. This makes kernel ebpf tethering offload happy.
+ // This hack should be reverted once we have the kernel fixed up.
+ // Note: this will automatically clamp to at least 1280 (ipv6 minimum mtu)
+ // see RouterAdvertisementDaemon.java putMtu()
+ params.mtu = v6only.getMtu() - 16;
params.hasDefaultRoute = v6only.hasIpv6DefaultRoute();
if (params.hasDefaultRoute) params.hopLimit = getHopLimit(v6only.getInterfaceName());