[PATCH bpf-next v3 3/3] selftests/bpf: check program redirect in xdp_cpumap_attach

["Alexis Lothoré (eBPF Foundation)" <alexis.lothore@bootlin.com>]

xdp_cpumap_attach, in its current form, only checks that an xdp cpumap
program can be executed, but not that it performs correctly the cpu
redirect as configured by userspace (bpf_prog_test_run_opts will return
success even if the redirect program returns an error)

Add a check to ensure that the program performs the configured redirect
as well. The check is based on a global variable incremented by a
chained program executed only if the redirect program properly executes.

Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
---
Changes in v3:
- new patch
---
 tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c     | 10 ++++++++--
 .../testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c |  5 +++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
index 31c225f0239613f6b5adad36b5b0e6e85eeddd9a..57d1661dc72aeb152c7cb9c2f63e3b47bf1799d8 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
@@ -62,8 +62,11 @@ static void test_xdp_with_cpumap_helpers(void)
 	err = bpf_prog_test_run_opts(prog_redir_fd, &opts);
 	ASSERT_OK(err, "XDP test run");
 
-	/* wait for the packets to be flushed */
+	/* wait for the packets to be flushed, then check that redirect has been
+	 * performed
+	 */
 	kern_sync_rcu();
+	ASSERT_NEQ(skel->bss->redirect_count, 0, "redirected packets");
 
 	err = bpf_xdp_detach(IFINDEX_LO, XDP_FLAGS_SKB_MODE, NULL);
 	ASSERT_OK(err, "XDP program detach");
@@ -203,8 +206,11 @@ static void test_xdp_with_cpumap_helpers_veth(void)
 	err = bpf_prog_test_run_opts(cm_fd_redir, &opts);
 	ASSERT_OK(err, "XDP test run");
 
-	/* wait for the packets to be flushed */
+	/* wait for the packets to be flushed, then check that redirect has been
+	 * performed
+	 */
 	kern_sync_rcu();
+	ASSERT_NEQ(skel->bss->redirect_count, 0, "redirected packets");
 
 	err = bpf_xdp_detach(ifindex_src, XDP_FLAGS_DRV_MODE, NULL);
 	ASSERT_OK(err, "XDP program detach");
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c b/tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c
index d848fe96924e32a72e1e0327e3afffeb349b933e..3619239b01b741dfd81bbebf5d9a62e0cf71e4f4 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c
@@ -12,6 +12,8 @@ struct {
 	__uint(max_entries, 4);
 } cpu_map SEC(".maps");
 
+__u32 redirect_count = 0;
+
 SEC("xdp")
 int xdp_redir_prog(struct xdp_md *ctx)
 {
@@ -27,6 +29,9 @@ int xdp_dummy_prog(struct xdp_md *ctx)
 SEC("xdp/cpumap")
 int xdp_dummy_cm(struct xdp_md *ctx)
 {
+	if (bpf_get_smp_processor_id() == 0)
+		redirect_count++;
+
 	if (ctx->ingress_ifindex == IFINDEX_LO)
 		return XDP_DROP;
 

-- 
2.46.2