netdev - [PATCH bpf-next 2/2] selftests/bpf: Add a test for maximum packet size in xdp_do

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Date:   Thu, 10 Mar 2022 23:56:21 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Shuah Khan <shuah@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH bpf-next 2/2] selftests/bpf: Add a test for maximum packet size in xdp_do_redirect

This adds an extra test to the xdp_do_redirect selftest for XDP live packet
mode, which verifies that the maximum permissible packet size is accepted
without any errors, and that a too big packet is correctly rejected.

Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 .../bpf/prog_tests/xdp_do_redirect.c          | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c b/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c
index 9926b07e38c8..a50971c6cf4a 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c
@@ -62,6 +62,28 @@ static int attach_tc_prog(struct bpf_tc_hook *hook, int fd)
 	return 0;
 }
 
+/* The maximum permissible size is: PAGE_SIZE - sizeof(struct xdp_page_head) -
+ * sizeof(struct skb_shared_info) - XDP_PACKET_HEADROOM = 3368 bytes
+ */
+#define MAX_PKT_SIZE 3368
+static void test_max_pkt_size(int fd)
+{
+	char data[MAX_PKT_SIZE + 1] = {};
+	int err;
+	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
+			    .data_in = &data,
+			    .data_size_in = MAX_PKT_SIZE,
+			    .flags = BPF_F_TEST_XDP_LIVE_FRAMES,
+			    .repeat = 1,
+		);
+	err = bpf_prog_test_run_opts(fd, &opts);
+	ASSERT_OK(err, "prog_run_max_size");
+
+	opts.data_size_in += 1;
+	err = bpf_prog_test_run_opts(fd, &opts);
+	ASSERT_EQ(err, -EINVAL, "prog_run_too_big");
+}
+
 #define NUM_PKTS 10000
 void test_xdp_do_redirect(void)
 {
@@ -167,6 +189,8 @@ void test_xdp_do_redirect(void)
 	ASSERT_EQ(skel->bss->pkts_seen_zero, 2, "pkt_count_zero");
 	ASSERT_EQ(skel->bss->pkts_seen_tc, NUM_PKTS - 2, "pkt_count_tc");
 
+	test_max_pkt_size(bpf_program__fd(skel->progs.xdp_count_pkts));
+
 out_tc:
 	bpf_tc_hook_destroy(&tc_hook);
 out:
-- 
2.35.1