selftests/bpf: Add cgroup_skb/egress test for load_bytes_relative

When cgroup_skb/egress triggers the MAC header is not set. Added a
test that asserts reading MAC header is a -EFAULT but NET header
succeeds. The test result from within the eBPF program is stored in
an 1-element array map that the userspace then reads and asserts on.

Another assertion is added that reading from a large offset, past
the end of packet, returns -EFAULT.

Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/9028ccbea4385a620e69c0a104f469ffd655c01e.1591812755.git.zhuyifei@google.com

diff --git a/tools/testing/selftests/bpf/prog_tests/load_bytes_relative.c b/tools/testing/selftests/bpf/prog_tests/load_bytes_relative.c
new file mode 100644 (file)
index 0000000..c1168e4
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/load_bytes_relative.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <test_progs.h>
+#include <network_helpers.h>
+
+void test_load_bytes_relative(void)
+{
+       int server_fd, cgroup_fd, prog_fd, map_fd, client_fd;
+       int err;
+       struct bpf_object *obj;
+       struct bpf_program *prog;
+       struct bpf_map *test_result;
+       __u32 duration = 0;
+
+       __u32 map_key = 0;
+       __u32 map_value = 0;
+
+       cgroup_fd = test__join_cgroup("/load_bytes_relative");
+       if (CHECK_FAIL(cgroup_fd < 0))
+               return;
+
+       server_fd = start_server(AF_INET, SOCK_STREAM);
+       if (CHECK_FAIL(server_fd < 0))
+               goto close_cgroup_fd;
+
+       err = bpf_prog_load("./load_bytes_relative.o", BPF_PROG_TYPE_CGROUP_SKB,
+                           &obj, &prog_fd);
+       if (CHECK_FAIL(err))
+               goto close_server_fd;
+
+       test_result = bpf_object__find_map_by_name(obj, "test_result");
+       if (CHECK_FAIL(!test_result))
+               goto close_bpf_object;
+
+       map_fd = bpf_map__fd(test_result);
+       if (map_fd < 0)
+               goto close_bpf_object;
+
+       prog = bpf_object__find_program_by_name(obj, "load_bytes_relative");
+       if (CHECK_FAIL(!prog))
+               goto close_bpf_object;
+
+       err = bpf_prog_attach(prog_fd, cgroup_fd, BPF_CGROUP_INET_EGRESS,
+                             BPF_F_ALLOW_MULTI);
+       if (CHECK_FAIL(err))
+               goto close_bpf_object;
+
+       client_fd = connect_to_fd(AF_INET, SOCK_STREAM, server_fd);
+       if (CHECK_FAIL(client_fd < 0))
+               goto close_bpf_object;
+       close(client_fd);
+
+       err = bpf_map_lookup_elem(map_fd, &map_key, &map_value);
+       if (CHECK_FAIL(err))
+               goto close_bpf_object;
+
+       CHECK(map_value != 1, "bpf", "bpf program returned failure");
+
+close_bpf_object:
+       bpf_object__close(obj);
+
+close_server_fd:
+       close(server_fd);
+
+close_cgroup_fd:
+       close(cgroup_fd);
+}

diff --git a/tools/testing/selftests/bpf/progs/load_bytes_relative.c b/tools/testing/selftests/bpf/progs/load_bytes_relative.c
new file mode 100644 (file)
index 0000000..dc1d04a
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/load_bytes_relative.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright 2020 Google LLC.
+ */
+
+#include <errno.h>
+#include <linux/bpf.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+#include <bpf/bpf_helpers.h>
+
+struct {
+       __uint(type, BPF_MAP_TYPE_ARRAY);
+       __uint(max_entries, 1);
+       __type(key, __u32);
+       __type(value, __u32);
+} test_result SEC(".maps");
+
+SEC("cgroup_skb/egress")
+int load_bytes_relative(struct __sk_buff *skb)
+{
+       struct ethhdr eth;
+       struct iphdr iph;
+
+       __u32 map_key = 0;
+       __u32 test_passed = 0;
+
+       /* MAC header is not set by the time cgroup_skb/egress triggers */
+       if (bpf_skb_load_bytes_relative(skb, 0, &eth, sizeof(eth),
+                                       BPF_HDR_START_MAC) != -EFAULT)
+               goto fail;
+
+       if (bpf_skb_load_bytes_relative(skb, 0, &iph, sizeof(iph),
+                                       BPF_HDR_START_NET))
+               goto fail;
+
+       if (bpf_skb_load_bytes_relative(skb, 0xffff, &iph, sizeof(iph),
+                                       BPF_HDR_START_NET) != -EFAULT)
+               goto fail;
+
+       test_passed = 1;
+
+fail:
+       bpf_map_update_elem(&test_result, &map_key, &test_passed, BPF_ANY);
+
+       return 1;
+}