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 <bpoirier@xxxxxxxx> --- 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) { + msg = "<cannot read>"; + } print_entry_error(map_info, key, msg ? : strerror(lookup_errno), !!msg); @@ -774,6 +778,11 @@ static int do_dump(int argc, char **argv) } } + if (info.type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY && + info.value_size != 8) { + p_info("Warning: cannot read values from %s map with value_size != 8", + map_type_name[info.type]); + } while (true) { err = bpf_map_get_next_key(fd, prev_key, key); if (err) { -- 2.21.0