[vnet] Set MTU for the VNET bridge RIF in BITMAP implementation (#1271)

Signed-off-by: Volodymyr Samotiy <[email protected]>

Author: Volodymyr Samotiy

orchagent/vnetorch.cpp

@@ -429,6 +429,10 @@ VnetBridgeInfo VNetBitmapObject::getBridgeInfoByVni(uint32_t vni, string tunnelN
     attr.value.oid = info.bridge_id;
     rif_attrs.push_back(attr);
 
+    attr.id = SAI_ROUTER_INTERFACE_ATTR_MTU;
+    attr.value.u32 = VNET_BITMAP_RIF_MTU;
+    rif_attrs.push_back(attr);
+
     status = sai_router_intfs_api->create_router_interface(
             &info.rif_id,
             gSwitchId,

orchagent/vnetorch.h

@@ -17,6 +17,7 @@
 #define VNET_TUNNEL_SIZE 40960
 #define VNET_NEIGHBOR_MAX 0xffff
 #define VXLAN_ENCAP_TTL 128
+#define VNET_BITMAP_RIF_MTU 9100
 
 extern sai_object_id_t gVirtualRouterId;