add another bridge-router-bridge test (test_brb2)

  o router is implemented as a namespace, similar to test_brb.
  o using linux bridge to provide bridge functionality.
    In test_brb, a simple bpf program implemented limited
    bridge functionality.
  o on my local box, test_brb performance is roughly 12% better
    than test_brb2.
Signed-off-by: Yonghong Song <yhs@plumgrid.com>

tests/cc/CMakeLists.txt

@@ -18,3 +18,5 @@ add_test(NAME py_test_trace3_c WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_trace3_c sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_trace3.py test_trace3.c)
 add_test(NAME py_test_brb WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
   COMMAND ${TEST_WRAPPER} py_brb_c sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_brb.py test_brb.c)
+add_test(NAME py_test_brb2 WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+  COMMAND ${TEST_WRAPPER} py_brb2_c sudo ${CMAKE_CURRENT_SOURCE_DIR}/test_brb2.py test_brb2.c)

tests/cc/test_brb2.c

+// Copyright (c) PLUMgrid, Inc.
+// Licensed under the Apache License, Version 2.0 (the "License")
+#include <bcc/proto.h>
+
+// physical endpoint manager (pem) tables which connects VMs and bridges
+// <ifindex_in, ifindex_out>
+BPF_TABLE("hash", u32, u32, pem_dest, 256);
+// <0, tx_pkts>
+BPF_TABLE("array", u32, u32, pem_stats, 1);
+
+BPF_EXPORT(pem)
+int pem(struct __sk_buff *skb) {
+    u32 ifindex_in, *ifindex_p;
+
+    ifindex_in = skb->ingress_ifindex;
+    ifindex_p = pem_dest.lookup(&ifindex_in);
+    if (ifindex_p) {
+#if 1
+        /* accumulate stats */
+        u32 index = 0;
+        u32 *value = pem_stats.lookup(&index);
+        if (value)
+            lock_xadd(value, 1);
+#endif
+        bpf_clone_redirect(skb, *ifindex_p, 0);
+    }
+
+    return 0;
+}