Currently when map a lookup is failed, user space API can not make any distinction whether given key was not found or lookup is not supported by particular map.
In this series we modify return value of maps which do not support lookup. Lookup on such map implementation will return -EOPNOTSUPP. bpf() syscall with BPF_MAP_LOOKUP_ELEM command will set EOPNOTSUPP errno. We also handle this error in bpftool to print appropriate message. Patch 1: adds handling of BPF_MAP_LOOKUP ELEM command of bpf syscall such that errno will set to EOPNOTSUPP when map doesn't support lookup Patch 2: Modifies the return value of map_lookup_elem() to EOPNOTSUPP for maps which do not support lookup Patch 3: Splits do_dump() in bpftool/map.c. Element printing code is moved out into new function dump_map_elem(). This was done in order to reduce deep indentation and accomodate further changes. Patch 4: Changes to bpftool to do additional checking for errno when map lookup is failed. In case of EOPNOTSUPP errno, it prints message "lookup not supported for this map" Prashant Bhole (4): bpf: error handling when map_lookup_elem isn't supported bpf: return EOPNOTSUPP when map lookup isn't supported tools/bpf: bpftool, split the function do_dump() tools/bpf: handle EOPNOTSUPP when map lookup is failed kernel/bpf/arraymap.c | 2 +- kernel/bpf/sockmap.c | 2 +- kernel/bpf/stackmap.c | 2 +- kernel/bpf/syscall.c | 9 +++- kernel/bpf/xskmap.c | 2 +- tools/bpf/bpftool/main.h | 5 ++ tools/bpf/bpftool/map.c | 108 +++++++++++++++++++++++++++------------ 7 files changed, 90 insertions(+), 40 deletions(-) -- 2.17.1
