[bpf-next] bpftool: Improve handling of ENOENT on map dumps

Message ID 20181108210007.6576-1-dsahern@kernel.org
State Accepted
Delegated to: BPF Maintainers
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Series
  • [bpf-next] bpftool: Improve handling of ENOENT on map dumps
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Commit Message

David Ahern Nov. 8, 2018, 9 p.m.
From: David Ahern <dsahern@gmail.com>

bpftool output is not user friendly when dumping a map with only a few
populated entries:

    $ bpftool map
    1: devmap  name tx_devmap  flags 0x0
            key 4B  value 4B  max_entries 64  memlock 4096B
    2: array  name tx_idxmap  flags 0x0
            key 4B  value 4B  max_entries 64  memlock 4096B

    $ bpftool map dump id 1
    key:
    00 00 00 00
    value:
    No such file or directory
    key:
    01 00 00 00
    value:
    No such file or directory
    key:
    02 00 00 00
    value:
    No such file or directory
    key: 03 00 00 00  value: 03 00 00 00

Handle ENOENT by keeping the line format sane and dumping
"<no entry>" for the value

    $ bpftool map dump id 1
    key: 00 00 00 00  value: <no entry>
    key: 01 00 00 00  value: <no entry>
    key: 02 00 00 00  value: <no entry>
    key: 03 00 00 00  value: 03 00 00 00
    ...

Signed-off-by: David Ahern <dsahern@gmail.com>
---
Alternatively, could just omit the value, so:
key: 00 00 00 00  value:
key: 01 00 00 00  value:
key: 02 00 00 00  value:
key: 03 00 00 00  value: 03 00 00 00

 tools/bpf/bpftool/map.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

Comments

Jakub Kicinski Nov. 8, 2018, 9:25 p.m. | #1
On Thu,  8 Nov 2018 13:00:07 -0800, David Ahern wrote:
> From: David Ahern <dsahern@gmail.com>
> 
> bpftool output is not user friendly when dumping a map with only a few
> populated entries:
> 
>     $ bpftool map
>     1: devmap  name tx_devmap  flags 0x0
>             key 4B  value 4B  max_entries 64  memlock 4096B
>     2: array  name tx_idxmap  flags 0x0
>             key 4B  value 4B  max_entries 64  memlock 4096B
> 
>     $ bpftool map dump id 1
>     key:
>     00 00 00 00
>     value:
>     No such file or directory
>     key:
>     01 00 00 00
>     value:
>     No such file or directory
>     key:
>     02 00 00 00
>     value:
>     No such file or directory
>     key: 03 00 00 00  value: 03 00 00 00
> 
> Handle ENOENT by keeping the line format sane and dumping
> "<no entry>" for the value
> 
>     $ bpftool map dump id 1
>     key: 00 00 00 00  value: <no entry>
>     key: 01 00 00 00  value: <no entry>
>     key: 02 00 00 00  value: <no entry>
>     key: 03 00 00 00  value: 03 00 00 00
>     ...
> 
> Signed-off-by: David Ahern <dsahern@gmail.com>

Seems good.  I wonder why "fd" maps report all indexes in get_next..

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

> Alternatively, could just omit the value, so:
> key: 00 00 00 00  value:
> key: 01 00 00 00  value:
> key: 02 00 00 00  value:
> key: 03 00 00 00  value: 03 00 00 00
> 
>  tools/bpf/bpftool/map.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index 101b8a881225..1f0060644e0c 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -383,7 +383,10 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
>  		printf(single_line ? "  " : "\n");
>  
>  		printf("value:%c", break_names ? '\n' : ' ');
> -		fprint_hex(stdout, value, info->value_size, " ");
> +		if (value)
> +			fprint_hex(stdout, value, info->value_size, " ");
> +		else
> +			printf("<no entry>");
>  
>  		printf("\n");
>  	} else {
> @@ -398,8 +401,12 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
>  		for (i = 0; i < n; i++) {
>  			printf("value (CPU %02d):%c",
>  			       i, info->value_size > 16 ? '\n' : ' ');
> -			fprint_hex(stdout, value + i * step,
> -				   info->value_size, " ");
> +			if (value) {
> +				fprint_hex(stdout, value + i * step,
> +					   info->value_size, " ");
> +			} else {
> +				printf("<no entry>");
> +			}

nit: in other places you don't add { }

>  			printf("\n");
>  		}
>  	}
> @@ -731,7 +738,11 @@ static int dump_map_elem(int fd, void *key, void *value,
>  		jsonw_string_field(json_wtr, "error", strerror(lookup_errno));
>  		jsonw_end_object(json_wtr);
>  	} else {
> -		print_entry_error(map_info, key, strerror(lookup_errno));
> +		if (errno == ENOENT)
> +			print_entry_plain(map_info, key, NULL);
> +		else
> +			print_entry_error(map_info, key,
> +					  strerror(lookup_errno));
>  	}
>  
>  	return 0;
Daniel Borkmann Nov. 9, 2018, 9:10 a.m. | #2
On 11/08/2018 10:25 PM, Jakub Kicinski wrote:
> On Thu,  8 Nov 2018 13:00:07 -0800, David Ahern wrote:
>> From: David Ahern <dsahern@gmail.com>
>>
>> bpftool output is not user friendly when dumping a map with only a few
>> populated entries:
>>
>>     $ bpftool map
>>     1: devmap  name tx_devmap  flags 0x0
>>             key 4B  value 4B  max_entries 64  memlock 4096B
>>     2: array  name tx_idxmap  flags 0x0
>>             key 4B  value 4B  max_entries 64  memlock 4096B
>>
>>     $ bpftool map dump id 1
>>     key:
>>     00 00 00 00
>>     value:
>>     No such file or directory
>>     key:
>>     01 00 00 00
>>     value:
>>     No such file or directory
>>     key:
>>     02 00 00 00
>>     value:
>>     No such file or directory
>>     key: 03 00 00 00  value: 03 00 00 00
>>
>> Handle ENOENT by keeping the line format sane and dumping
>> "<no entry>" for the value
>>
>>     $ bpftool map dump id 1
>>     key: 00 00 00 00  value: <no entry>
>>     key: 01 00 00 00  value: <no entry>
>>     key: 02 00 00 00  value: <no entry>
>>     key: 03 00 00 00  value: 03 00 00 00
>>     ...
>>
>> Signed-off-by: David Ahern <dsahern@gmail.com>
> 
> Seems good.  I wonder why "fd" maps report all indexes in get_next..
> 
> Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> 
>> Alternatively, could just omit the value, so:
>> key: 00 00 00 00  value:
>> key: 01 00 00 00  value:
>> key: 02 00 00 00  value:
>> key: 03 00 00 00  value: 03 00 00 00
>>
>>  tools/bpf/bpftool/map.c | 19 +++++++++++++++----
>>  1 file changed, 15 insertions(+), 4 deletions(-)
>>
>> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
>> index 101b8a881225..1f0060644e0c 100644
>> --- a/tools/bpf/bpftool/map.c
>> +++ b/tools/bpf/bpftool/map.c
>> @@ -383,7 +383,10 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
>>  		printf(single_line ? "  " : "\n");
>>  
>>  		printf("value:%c", break_names ? '\n' : ' ');
>> -		fprint_hex(stdout, value, info->value_size, " ");
>> +		if (value)
>> +			fprint_hex(stdout, value, info->value_size, " ");
>> +		else
>> +			printf("<no entry>");
>>  
>>  		printf("\n");
>>  	} else {
>> @@ -398,8 +401,12 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
>>  		for (i = 0; i < n; i++) {
>>  			printf("value (CPU %02d):%c",
>>  			       i, info->value_size > 16 ? '\n' : ' ');
>> -			fprint_hex(stdout, value + i * step,
>> -				   info->value_size, " ");
>> +			if (value) {
>> +				fprint_hex(stdout, value + i * step,
>> +					   info->value_size, " ");
>> +			} else {
>> +				printf("<no entry>");
>> +			}
> 
> nit: in other places you don't add { }

Applied to bpf-next and fixed this nit up while doing so, thanks everyone!

Patch

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 101b8a881225..1f0060644e0c 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -383,7 +383,10 @@  static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
 		printf(single_line ? "  " : "\n");
 
 		printf("value:%c", break_names ? '\n' : ' ');
-		fprint_hex(stdout, value, info->value_size, " ");
+		if (value)
+			fprint_hex(stdout, value, info->value_size, " ");
+		else
+			printf("<no entry>");
 
 		printf("\n");
 	} else {
@@ -398,8 +401,12 @@  static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
 		for (i = 0; i < n; i++) {
 			printf("value (CPU %02d):%c",
 			       i, info->value_size > 16 ? '\n' : ' ');
-			fprint_hex(stdout, value + i * step,
-				   info->value_size, " ");
+			if (value) {
+				fprint_hex(stdout, value + i * step,
+					   info->value_size, " ");
+			} else {
+				printf("<no entry>");
+			}
 			printf("\n");
 		}
 	}
@@ -731,7 +738,11 @@  static int dump_map_elem(int fd, void *key, void *value,
 		jsonw_string_field(json_wtr, "error", strerror(lookup_errno));
 		jsonw_end_object(json_wtr);
 	} else {
-		print_entry_error(map_info, key, strerror(lookup_errno));
+		if (errno == ENOENT)
+			print_entry_plain(map_info, key, NULL);
+		else
+			print_entry_error(map_info, key,
+					  strerror(lookup_errno));
 	}
 
 	return 0;