Re: [PATCH v2 bpf-next 2/2] bpftool: Improve handling of ENOSPC on reuseport_array map dumps

[Quentin Monnet]

2019-04-12 12:03 UTC+0900 ~ Benjamin Poirier <bpoir...@suse.com>
avoids outputting a series of
        value:
        No space left on device
The value itself is not wrong but bpf_fd_reuseport_array_lookup_elem() can
only return it if the map was created with value_size = 8. There's nothing
bpftool can do about it. Instead of repeating this error for every key in
the map, print an explanatory warning and a specialized error.

example before:
key: 00 00 00 00
value:
No space left on device
key: 01 00 00 00
value:
No space left on device
key: 02 00 00 00
value:
No space left on device
Found 0 elements

example after:
Warning: cannot read values from reuseport_sockarray map with value_size != 8
key: 00 00 00 00  value: <cannot read>
key: 01 00 00 00  value: <cannot read>
key: 02 00 00 00  value: <cannot read>
Found 0 elements

Signed-off-by: Benjamin Poirier <bpoir...@suse.com>
---
  tools/bpf/bpftool/map.c | 11 ++++++++++-
  1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 71840faaeab5..e6d72f777767 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -716,8 +716,12 @@ static int dump_map_elem(int fd, void *key, void *value,
        } else {
                const char *msg = NULL;
  
-		if (errno == ENOENT)
+               if (lookup_errno == ENOENT) {
                        msg = "<no entry>";
+               } else if (lookup_errno == ENOSPC && map_info->type ==
+                        BPF_MAP_TYPE_REUSEPORT_SOCKARRAY) {

Nit: This should be aligned on the open parenthesis (And preferably 
split after the "&&", if the second condition fits on its own line?).

Thanks for the changes! This version looks much better to me than v1.

Quentin