selftests/xsk: Query for native XDP support

Currently, xdpxceiver assumes that underlying device supports XDP in
native mode - it is fine by now since tests can run only on a veth pair.
Future commit is going to allow running test suite against physical
devices, so let us query the device if it is capable of running XDP
programs in native mode. This way xdpxceiver will not try to run
TEST_MODE_DRV if device being tested is not supporting it.
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20220901114813.16275-2-maciej.fijalkowski@intel.com

tools/testing/selftests/bpf/xskxceiver.c

@@ -99,6 +99,8 @@
 #include <stdatomic.h>
 #include "xsk.h"
 #include "xskxceiver.h"
+#include <bpf/bpf.h>
+#include <linux/filter.h>
 #include "../kselftest.h"
 
 /* AF_XDP APIs were moved into libxdp and marked as deprecated in libbpf.
@@ -1712,10 +1714,40 @@ static void ifobject_delete(struct ifobject *ifobj)
 	free(ifobj);
 }
 
+static bool is_xdp_supported(struct ifobject *ifobject)
+{
+	int flags = XDP_FLAGS_DRV_MODE;
+
+	LIBBPF_OPTS(bpf_link_create_opts, opts, .flags = flags);
+	struct bpf_insn insns[2] = {
+		BPF_MOV64_IMM(BPF_REG_0, XDP_PASS),
+		BPF_EXIT_INSN()
+	};
+	int ifindex = if_nametoindex(ifobject->ifname);
+	int prog_fd, insn_cnt = ARRAY_SIZE(insns);
+	int err;
+
+	prog_fd = bpf_prog_load(BPF_PROG_TYPE_XDP, NULL, "GPL", insns, insn_cnt, NULL);
+	if (prog_fd < 0)
+		return false;
+
+	err = bpf_xdp_attach(ifindex, prog_fd, flags, NULL);
+	if (err) {
+		close(prog_fd);
+		return false;
+	}
+
+	bpf_xdp_detach(ifindex, flags, NULL);
+	close(prog_fd);
+
+	return true;
+}
+
 int main(int argc, char **argv)
 {
 	struct pkt_stream *pkt_stream_default;
 	struct ifobject *ifobj_tx, *ifobj_rx;
+	int modes = TEST_MODE_SKB + 1;
 	u32 i, j, failed_tests = 0;
 	struct test_spec test;
 
@@ -1743,15 +1775,18 @@ int main(int argc, char **argv)
 	init_iface(ifobj_rx, MAC2, MAC1, IP2, IP1, UDP_PORT2, UDP_PORT1,
 		   worker_testapp_validate_rx);
 
+	if (is_xdp_supported(ifobj_tx))
+		modes++;
+
 	test_spec_init(&test, ifobj_tx, ifobj_rx, 0);
 	pkt_stream_default = pkt_stream_generate(ifobj_tx->umem, DEFAULT_PKT_CNT, PKT_SIZE);
 	if (!pkt_stream_default)
 		exit_with_error(ENOMEM);
 	test.pkt_stream_default = pkt_stream_default;
 
-	ksft_set_plan(TEST_MODE_MAX * TEST_TYPE_MAX);
+	ksft_set_plan(modes * TEST_TYPE_MAX);
 
-	for (i = 0; i < TEST_MODE_MAX; i++)
+	for (i = 0; i < modes; i++)
 		for (j = 0; j < TEST_TYPE_MAX; j++) {
 			test_spec_init(&test, ifobj_tx, ifobj_rx, i);
 			run_pkt_test(&test, i, j);