netdev - [PATCH bpf 2/4] selftests: bpf: ignore RST packets for reuseport tests

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Message-Id: <20200123165934.9584-3-lmb@cloudflare.com>
Date:   Thu, 23 Jan 2020 16:59:31 +0000
From:   Lorenz Bauer <lmb@...udflare.com>
To:     Shuah Khan <shuah@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>
Cc:     Lorenz Bauer <lmb@...udflare.com>, linux-kselftest@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH bpf 2/4] selftests: bpf: ignore RST packets for reuseport tests

The reuseport tests currently suffer from a race condition: RST
packets count towards DROP_ERR_SKB_DATA, since they don't contain
a valid struct cmd. Tests will spuriously fail depending on whether
check_results is called before or after the RST is processed.

Exit the BPF program early if FIN is set.

Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
---
 .../selftests/bpf/progs/test_select_reuseport_kern.c        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/test_select_reuseport_kern.c b/tools/testing/selftests/bpf/progs/test_select_reuseport_kern.c
index d69a1f2bbbfd..26e77dcc7e91 100644
--- a/tools/testing/selftests/bpf/progs/test_select_reuseport_kern.c
+++ b/tools/testing/selftests/bpf/progs/test_select_reuseport_kern.c
@@ -113,6 +113,12 @@ int _select_by_skb_data(struct sk_reuseport_md *reuse_md)
 		data_check.skb_ports[0] = th->source;
 		data_check.skb_ports[1] = th->dest;
 
+		if (th->fin)
+			/* The connection is being torn down at the end of a
+			 * test. It can't contain a cmd, so return early.
+			 */
+			return SK_PASS;
+
 		if ((th->doff << 2) + sizeof(*cmd) > data_check.len)
 			GOTO_DONE(DROP_ERR_SKB_DATA);
 		if (bpf_skb_load_bytes(reuse_md, th->doff << 2, &cmd_copy,
-- 
2.20.1