[PATCH bpf-next 12/15] selftests/xsk: add test when some packets are XDP_DROPed

[Magnus Karlsson <magnus.karlsson@gmail.com>]

From: Magnus Karlsson <magnus.karlsson@intel.com>

Add a new test where some of the packets are not passed to the AF_XDP
socket and instead get a XDP_DROP verdict. This is important as it
tests the recycling mechanism of the buffer pool. If a packet is not
sent to the AF_XDP socket, the buffer the packet resides in is instead
recycled so it can be used again without the round-trip to user
space. The test introduces a new XDP program that drops every other
packet.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
 tools/testing/selftests/bpf/Makefile          |  2 +-
 .../selftests/bpf/progs/xsk_xdp_drop.c        | 25 ++++++++++
 tools/testing/selftests/bpf/xskxceiver.c      | 48 +++++++++++++++++--
 tools/testing/selftests/bpf/xskxceiver.h      |  3 ++
 4 files changed, 72 insertions(+), 6 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/xsk_xdp_drop.c

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 42e15b5a34a7..77ef8a8e6db4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -240,7 +240,7 @@ $(OUTPUT)/flow_dissector_load: $(TESTING_HELPERS)
 $(OUTPUT)/test_maps: $(TESTING_HELPERS)
 $(OUTPUT)/test_verifier: $(TESTING_HELPERS) $(CAP_HELPERS)
 $(OUTPUT)/xsk.o: $(BPFOBJ)
-$(OUTPUT)/xskxceiver: $(OUTPUT)/xsk.o $(OUTPUT)/xsk_def_prog.skel.h
+$(OUTPUT)/xskxceiver: $(OUTPUT)/xsk.o $(OUTPUT)/xsk_def_prog.skel.h $(OUTPUT)/xsk_xdp_drop.skel.h
 
 BPFTOOL ?= $(DEFAULT_BPFTOOL)
 $(DEFAULT_BPFTOOL): $(wildcard $(BPFTOOLDIR)/*.[ch] $(BPFTOOLDIR)/Makefile)    \
diff --git a/tools/testing/selftests/bpf/progs/xsk_xdp_drop.c b/tools/testing/selftests/bpf/progs/xsk_xdp_drop.c
new file mode 100644
index 000000000000..12a12b0d9fc1
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/xsk_xdp_drop.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Intel */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_XSKMAP);
+	__uint(max_entries, 1);
+	__uint(key_size, sizeof(int));
+	__uint(value_size, sizeof(int));
+} xsk SEC(".maps");
+
+static unsigned int idx;
+
+SEC("xdp") int xsk_xdp_drop(struct xdp_md *xdp)
+{
+	/* Drop every other packet */
+	if (idx++ % 2)
+		return XDP_DROP;
+
+	return bpf_redirect_map(&xsk, 0, XDP_DROP);
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
index 0cda4e3f1871..522dc1d69c17 100644
--- a/tools/testing/selftests/bpf/xskxceiver.c
+++ b/tools/testing/selftests/bpf/xskxceiver.c
@@ -1654,18 +1654,53 @@ static void testapp_invalid_desc(struct test_spec *test)
 	pkt_stream_restore_default(test);
 }
 
-static int xsk_load_xdp_program(struct ifobject *ifobj)
+static void testapp_xdp_drop(struct test_spec *test)
+{
+	struct ifobject *ifobj = test->ifobj_rx;
+	int err;
+
+	test_spec_set_name(test, "XDP_CONSUMES_SOME_PACKETS");
+	xsk_detach_xdp_program(ifobj->ifindex, ifobj->xdp_flags);
+	err = xsk_attach_xdp_program(ifobj->xdp_drop->progs.xsk_xdp_drop, ifobj->ifindex,
+				     ifobj->xdp_flags);
+	if (err) {
+		printf("Error attaching XDP_DROP program\n");
+		test->fail = true;
+		return;
+	}
+	ifobj->xskmap = ifobj->xdp_drop->maps.xsk;
+
+	pkt_stream_receive_half(test);
+	testapp_validate_traffic(test);
+
+	pkt_stream_restore_default(test);
+	xsk_detach_xdp_program(ifobj->ifindex, ifobj->xdp_flags);
+	err = xsk_attach_xdp_program(ifobj->def_prog->progs.xsk_def_prog, ifobj->ifindex,
+				     ifobj->xdp_flags);
+	if (err) {
+		printf("Error restoring default XDP program\n");
+		exit_with_error(-err);
+	}
+	ifobj->xskmap = ifobj->def_prog->maps.xsk;
+}
+
+static int xsk_load_xdp_programs(struct ifobject *ifobj)
 {
 	ifobj->def_prog = xsk_def_prog__open_and_load();
 	if (libbpf_get_error(ifobj->def_prog))
 		return libbpf_get_error(ifobj->def_prog);
 
+	ifobj->xdp_drop = xsk_xdp_drop__open_and_load();
+	if (libbpf_get_error(ifobj->xdp_drop))
+		return libbpf_get_error(ifobj->xdp_drop);
+
 	return 0;
 }
 
-static void xsk_unload_xdp_program(struct ifobject *ifobj)
+static void xsk_unload_xdp_programs(struct ifobject *ifobj)
 {
 	xsk_def_prog__destroy(ifobj->def_prog);
+	xsk_xdp_drop__destroy(ifobj->xdp_drop);
 }
 
 static void init_iface(struct ifobject *ifobj, const char *dst_mac, const char *src_mac,
@@ -1692,7 +1727,7 @@ static void init_iface(struct ifobject *ifobj, const char *dst_mac, const char *
 	if (!load_xdp)
 		return;
 
-	err = xsk_load_xdp_program(ifobj);
+	err = xsk_load_xdp_programs(ifobj);
 	if (err) {
 		printf("Error loading XDP program\n");
 		exit_with_error(err);
@@ -1804,6 +1839,9 @@ static void run_pkt_test(struct test_spec *test, enum test_mode mode, enum test_
 	case TEST_TYPE_HEADROOM:
 		testapp_headroom(test);
 		break;
+	case TEST_TYPE_XDP_CONSUMES_PACKETS:
+		testapp_xdp_drop(test);
+		break;
 	default:
 		break;
 	}
@@ -1971,8 +2009,8 @@ int main(int argc, char **argv)
 
 	pkt_stream_delete(tx_pkt_stream_default);
 	pkt_stream_delete(rx_pkt_stream_default);
-	xsk_unload_xdp_program(ifobj_tx);
-	xsk_unload_xdp_program(ifobj_rx);
+	xsk_unload_xdp_programs(ifobj_tx);
+	xsk_unload_xdp_programs(ifobj_rx);
 	ifobject_delete(ifobj_tx);
 	ifobject_delete(ifobj_rx);
 
diff --git a/tools/testing/selftests/bpf/xskxceiver.h b/tools/testing/selftests/bpf/xskxceiver.h
index eb6355bcc143..3483ac240b2e 100644
--- a/tools/testing/selftests/bpf/xskxceiver.h
+++ b/tools/testing/selftests/bpf/xskxceiver.h
@@ -6,6 +6,7 @@
 #define XSKXCEIVER_H_
 
 #include "xsk_def_prog.skel.h"
+#include "xsk_xdp_drop.skel.h"
 
 #ifndef SOL_XDP
 #define SOL_XDP 283
@@ -87,6 +88,7 @@ enum test_type {
 	TEST_TYPE_STATS_RX_FULL,
 	TEST_TYPE_STATS_FILL_EMPTY,
 	TEST_TYPE_BPF_RES,
+	TEST_TYPE_XDP_CONSUMES_PACKETS,
 	TEST_TYPE_MAX
 };
 
@@ -141,6 +143,7 @@ struct ifobject {
 	validation_func_t validation_func;
 	struct pkt_stream *pkt_stream;
 	struct xsk_def_prog *def_prog;
+	struct xsk_xdp_drop *xdp_drop;
 	struct bpf_map *xskmap;
 	int ifindex;
 	u32 dst_ip;
-- 
2.34.1