selftests/bpf/test_offload.py: Filter bpftool internal map when counting maps

A few of the tests in test_offload.py expects to see a certain number of
maps created, and checks this by counting the number of maps returned by
bpftool. There is already a filter that will remove any maps already there
at the beginning of the test, but bpftool now creates a map for the PID
iterator rodata on each invocation, which makes the map count wrong. Fix
this by also filtering the pid_iter.rodata map by name when counting.

Fixes: d53dee3fe013 ("tools/bpftool: Show info for processes holding BPF map/prog/link/btf FDs")
Signed-off-by: Toke Høiland-Jørgensen <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Acked-by: Jakub Kicinski <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/testing/selftests/bpf/test_offload.py

···
 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)
+    maps = [m for m in maps if m not in base_maps and m.get('name') not in base_map_names]
     if expected is not None:
         if len(maps) != expected:
             fail(True, "%d BPF maps loaded, expected %d" %
···
 skip(ret != 0, "bpftool not installed")
 base_progs = progs
 _, base_maps = bpftool("map")
+base_map_names = [
+    'pid_iter.rodata' # created on each bpftool invocation
+]
 
 # Check netdevsim
 ret, out = cmd("modprobe netdevsim", fail=False)