selftests/bpf: test offloads even with BPF programs present

Modern distroes increasingly make use of BPF programs.  Default
Ubuntu 18.04 installation boots with a number of cgroup_skb
programs loaded.

test_offloads.py tries to check if programs and maps are not
leaked on error paths by confirming the list of programs on the
system is empty between tests.

Since we can no longer expect the system to have no BPF objects
at boot try to remember the programs and maps present at the start,
and skip those when scanning the system.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/testing/selftests/bpf/test_offload.py b/tools/testing/selftests/bpf/test_offload.py
index e78aad0a68bb9963368a5236377144c8e61cb230..be800d0e7a841abfbc60545cf63fe33219db0c35 100755 (executable)
--- a/tools/testing/selftests/bpf/test_offload.py
+++ b/tools/testing/selftests/bpf/test_offload.py
@@ -163,6 +163,10 @@ def bpftool(args, JSON=True, ns="", fail=True):
 
 def bpftool_prog_list(expected=None, ns=""):
     _, progs = bpftool("prog show", JSON=True, ns=ns, fail=True)
+    # Remove the base progs
+    for p in base_progs:
+        if p in progs:
+            progs.remove(p)
     if expected is not None:
         if len(progs) != expected:
             fail(True, "%d BPF programs loaded, expected %d" %
@@ -171,6 +175,10 @@ def bpftool_prog_list(expected=None, ns=""):
 
 def bpftool_map_list(expected=None, ns=""):
     _, maps = bpftool("map show", JSON=True, ns=ns, fail=True)
+    # Remove the base maps
+    for m in base_maps:
+        if m in maps:
+            maps.remove(m)
     if expected is not None:
         if len(maps) != expected:
             fail(True, "%d BPF maps loaded, expected %d" %
@@ -585,8 +593,8 @@ skip(os.getuid() != 0, "test must be run as root")
 # Check tools
 ret, progs = bpftool("prog", fail=False)
 skip(ret != 0, "bpftool not installed")
-# Check no BPF programs are loaded
-skip(len(progs) != 0, "BPF programs already loaded on the system")
+base_progs = progs
+_, base_maps = bpftool("map")
 
 # Check netdevsim
 ret, out = cmd("modprobe netdevsim", fail=False)