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Subject[BPF v1] tools: bpftool: Fix JSON output when lookup fails
Date
In commit 9a5ab8bf1d6d ("tools: bpftool: turn err() and info() macros
into functions") one case of error reporting was special cased, so it
could report a lookup error for a specific key when dumping the map
element. What the code forgot to do is to wrap the key and value keys
into a JSON object, so an example output of pretty JSON dump of a
sockhash map (which does not support looking up its values) is:

[
"key": ["0x0a","0x41","0x00","0x02","0x1f","0x78","0x00","0x00"
],
"value": {
"error": "Operation not supported"
},
"key": ["0x0a","0x41","0x00","0x02","0x1f","0x78","0x00","0x01"
],
"value": {
"error": "Operation not supported"
}
]

Note the key-value pairs inside the toplevel array. They should be
wrapped inside a JSON object, otherwise it is an invalid JSON. This
commit fixes this, so the output now is:

[{
"key": ["0x0a","0x41","0x00","0x02","0x1f","0x78","0x00","0x00"
],
"value": {
"error": "Operation not supported"
}
},{
"key": ["0x0a","0x41","0x00","0x02","0x1f","0x78","0x00","0x01"
],
"value": {
"error": "Operation not supported"
}
}
]

Fixes: 9a5ab8bf1d6d ("tools: bpftool: turn err() and info() macros into functions")
Cc: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Krzesimir Nowak <krzesimir@kinvolk.io>
---
tools/bpf/bpftool/map.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 3ec82904ccec..5da5a7311f13 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -716,12 +716,14 @@ static int dump_map_elem(int fd, void *key, void *value,
return 0;

if (json_output) {
+ jsonw_start_object(json_wtr);
jsonw_name(json_wtr, "key");
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", strerror(lookup_errno));
jsonw_end_object(json_wtr);
+ jsonw_end_object(json_wtr);
} else {
const char *msg = NULL;

--
2.20.1
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