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tools/bpf: bpftool, print strerror when map lookup error occurs

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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>
This commit is contained in:
Prashant Bhole 2018-10-09 10:04:52 +09:00 committed by Alexei Starovoitov
parent 18a781daa9
commit 8ec92dc22e
1 changed files with 24 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
tools/bpf/bpftool/map.c
View File

@ -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;