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Date:   Thu, 10 Oct 2019 20:17:50 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, kernel-team@...udflare.com,
        Stanislav Fomichev <sdf@...ichev.me>
Subject: [PATCH bpf-next v2 2/2] selftests/bpf: Check that flow dissector can be re-attached

Make sure a new flow dissector program can be attached to replace the old
one with a single syscall. Also check that attaching the same program twice
is prohibited.

Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
---
 .../bpf/prog_tests/flow_dissector_reattach.c  | 127 ++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c

diff --git a/tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c b/tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c
new file mode 100644
index 000000000000..fa502720825c
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/flow_dissector_reattach.c
@@ -0,1 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test that the flow_dissector program can be updated with a single
+ * syscall by attaching a new program that replaces the existing one.
+ *
+ * Corner case - the same program cannot be attached twice.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <stdbool.h>
+#include <unistd.h>
+
+#include <linux/bpf.h>
+#include <bpf/bpf.h>
+
+#include "test_progs.h"
+
+static bool is_attached(int netns)
+{
+	__u32 cnt;
+	int err;
+
+	err = bpf_prog_query(netns, BPF_FLOW_DISSECTOR, 0, NULL, NULL, &cnt);
+	if (CHECK_FAIL(err)) {
+		perror("bpf_prog_query");
+		return true; /* fail-safe */
+	}
+
+	return cnt > 0;
+}
+
+static int load_prog(void)
+{
+	struct bpf_insn prog[] = {
+		BPF_MOV64_IMM(BPF_REG_0, BPF_OK),
+		BPF_EXIT_INSN(),
+	};
+	int fd;
+
+	fd = bpf_load_program(BPF_PROG_TYPE_FLOW_DISSECTOR, prog,
+			      ARRAY_SIZE(prog), "GPL", 0, NULL, 0);
+	if (CHECK_FAIL(fd < 0))
+		perror("bpf_load_program");
+
+	return fd;
+}
+
+static void do_flow_dissector_reattach(void)
+{
+	int prog_fd[2] = { -1, -1 };
+	int err;
+
+	prog_fd[0] = load_prog();
+	if (prog_fd[0] < 0)
+		return;
+
+	prog_fd[1] = load_prog();
+	if (prog_fd[1] < 0)
+		goto out_close;
+
+	err = bpf_prog_attach(prog_fd[0], 0, BPF_FLOW_DISSECTOR, 0);
+	if (CHECK_FAIL(err)) {
+		perror("bpf_prog_attach-0");
+		goto out_close;
+	}
+
+	/* Expect success when attaching a different program */
+	err = bpf_prog_attach(prog_fd[1], 0, BPF_FLOW_DISSECTOR, 0);
+	if (CHECK_FAIL(err)) {
+		perror("bpf_prog_attach-1");
+		goto out_detach;
+	}
+
+	/* Expect failure when attaching the same program twice */
+	err = bpf_prog_attach(prog_fd[1], 0, BPF_FLOW_DISSECTOR, 0);
+	if (CHECK_FAIL(!err || errno != EINVAL))
+		perror("bpf_prog_attach-2");
+
+out_detach:
+	err = bpf_prog_detach(0, BPF_FLOW_DISSECTOR);
+	if (CHECK_FAIL(err))
+		perror("bpf_prog_detach");
+
+out_close:
+	close(prog_fd[1]);
+	close(prog_fd[0]);
+}
+
+void test_flow_dissector_reattach(void)
+{
+	int init_net, err;
+
+	init_net = open("/proc/1/ns/net", O_RDONLY);
+	if (CHECK_FAIL(init_net < 0)) {
+		perror("open(/proc/1/ns/net)");
+		return;
+	}
+
+	err = setns(init_net, CLONE_NEWNET);
+	if (CHECK_FAIL(err)) {
+		perror("setns(/proc/1/ns/net)");
+		goto out_close;
+	}
+
+	if (is_attached(init_net)) {
+		test__skip();
+		printf("Can't test with flow dissector attached to init_net\n");
+		return;
+	}
+
+	/* First run tests in root network namespace */
+	do_flow_dissector_reattach();
+
+	/* Then repeat tests in a non-root namespace */
+	err = unshare(CLONE_NEWNET);
+	if (CHECK_FAIL(err)) {
+		perror("unshare(CLONE_NEWNET)");
+		goto out_close;
+	}
+	do_flow_dissector_reattach();
+
+out_close:
+	close(init_net);
+}
-- 
2.20.1

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