selftests/net: Add test for loading devbound XDP program in generic mode

Add a test to bpf_offload.py for loading a devbound XDP program in
generic mode, checking that it fails correctly.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250127131344.238147-2-toke@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/bpf_offload.py

@@ -215,12 +215,14 @@ def bpftool_map_list_wait(expected=0, n_retry=20, ns=""):
     raise Exception("Time out waiting for map counts to stabilize want %d, have %d" % (expected, nmaps))
 
 def bpftool_prog_load(sample, file_name, maps=[], prog_type="xdp", dev=None,
-                      fail=True, include_stderr=False):
+                      fail=True, include_stderr=False, dev_bind=None):
     args = "prog load %s %s" % (os.path.join(bpf_test_dir, sample), file_name)
     if prog_type is not None:
         args += " type " + prog_type
     if dev is not None:
         args += " dev " + dev
+    elif dev_bind is not None:
+        args += " xdpmeta_dev " + dev_bind
     if len(maps):
         args += " map " + " map ".join(maps)
 
@@ -980,6 +982,16 @@ def test_multi_prog(simdev, sim, obj, modename, modeid):
     rm("/sys/fs/bpf/offload")
     sim.wait_for_flush()
 
+    bpftool_prog_load("sample_ret0.bpf.o", "/sys/fs/bpf/devbound",
+                      dev_bind=sim['ifname'])
+    devbound = bpf_pinned("/sys/fs/bpf/devbound")
+    start_test("Test dev-bound program in generic mode...")
+    ret, _, err = sim.set_xdp(devbound, "generic", fail=False, include_stderr=True)
+    fail(ret == 0, "devbound program in generic mode allowed")
+    check_extack(err, "Can't attach device-bound programs in generic mode.", args)
+    rm("/sys/fs/bpf/devbound")
+    sim.wait_for_flush()
+
     start_test("Test XDP load failure...")
     sim.dfs["dev/bpf_bind_verifier_accept"] = 0
     ret, _, err = bpftool_prog_load("sample_ret0.bpf.o", "/sys/fs/bpf/offload",