tools/bpf: bpftool, print strerror when map lookup error occurs (8ec92dc2) · Commits · 戴 / test

Since map lookup error can be ENOENT or EOPNOTSUPP, let's print strerror() as error message in normal and JSON output. This patch adds helper function print_entry_error() to print entry from lookup error occurs Example: Following example dumps a map which does not support lookup. Output before: root# bpftool map -jp dump id 40 [ "key": ["0x0a","0x00","0x00","0x00" ], "value": { "error": "can\'t lookup element" }, "key": ["0x0b","0x00","0x00","0x00" ], "value": { "error": "can\'t lookup element" } ] root# bpftool map dump id 40 can't lookup element with key: 0a 00 00 00 can't lookup element with key: 0b 00 00 00 Found 0 elements Output after changes: root# bpftool map dump -jp id 45 [ "key": ["0x0a","0x00","0x00","0x00" ], "value": { "error": "Operation not supported" }, "key": ["0x0b","0x00","0x00","0x00" ], "value": { "error": "Operation not supported" } ] root# bpftool map dump id 45 key: 0a 00 00 00 value: Operation not supported key: 0b 00 00 00 value: Operation not supported Found 0 elements Signed-off-by:

Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp> Acked-by:

Jakub Kicinski <jakub.kicinski@netronome.com> Acked-by:

Alexei Starovoitov <ast@kernel.org> Acked-by:

Song Liu <songliubraving@fb.com> Signed-off-by:

Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpftool/map.c

+24 −5

Original line number	Diff line number	Diff line
		@@ -336,6 +336,25 @@ static void print_entry_json(struct bpf_map_info info, unsigned char key,
		jsonw_end_object(json_wtr);
		}

		static void print_entry_error(struct bpf_map_info info, unsigned char key,
		const char *value)
		{
		int value_size = strlen(value);
		bool single_line, break_names;

		break_names = info->key_size > 16 \|\| value_size > 16;
		single_line = info->key_size + value_size <= 24 && !break_names;

		printf("key:%c", break_names ? '\n' : ' ');
		fprint_hex(stdout, key, info->key_size, " ");

		printf(single_line ? " " : "\n");

		printf("value:%c%s", break_names ? '\n' : ' ', value);

		printf("\n");
		}

		static void print_entry_plain(struct bpf_map_info info, unsigned char key,
		unsigned char *value)
		{
		@@ -663,6 +682,7 @@ static int dump_map_elem(int fd, void key, void value,
		json_writer_t *btf_wtr)
		{
		int num_elems = 0;
		int lookup_errno;

		if (!bpf_map_lookup_elem(fd, key, value)) {
		if (json_output) {
		@@ -685,6 +705,8 @@ static int dump_map_elem(int fd, void key, void value,
		}

		/* lookup error handling */
		lookup_errno = errno;

		if (map_is_map_of_maps(map_info->type) \|\|
		map_is_map_of_progs(map_info->type))
		return 0;
		@@ -694,13 +716,10 @@ static int dump_map_elem(int fd, void key, void value,
		print_hex_data_json(key, map_info->key_size);
		jsonw_name(json_wtr, "value");
		jsonw_start_object(json_wtr);
		jsonw_string_field(json_wtr, "error",
		"can't lookup element");
		jsonw_string_field(json_wtr, "error", strerror(lookup_errno));
		jsonw_end_object(json_wtr);
		} else {
		p_info("can't lookup element with key: ");
		fprint_hex(stderr, key, map_info->key_size, " ");
		fprintf(stderr, "\n");
		print_entry_error(map_info, key, strerror(lookup_errno));
		}

		return 0;

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