netdev - Re: [PATCH bpf-next 0/6] Error handling when map lookup isn't supported

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Message-ID: <20181005183512.lmjbgf2qoene3r4w@ast-mbp.dhcp.thefacebook.com>
Date:   Fri, 5 Oct 2018 11:35:13 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        "David S . Miller" <davem@...emloft.net>,
        Quentin Monnet <quentin.monnet@...ronome.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next 0/6] Error handling when map lookup isn't
 supported

On Fri, Oct 05, 2018 at 12:35:55PM +0900, Prashant Bhole wrote:
> Currently when map a lookup fails, 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 in bpftool to print strerror() message when lookup
> error is occured. This will result in appropriate message like
> "Operation not supported" when map doesn't support lookup.
> 
> Patch 5: test_verifier: change fixup map naming convention as
> suggested by Alexei
> 
> Patch 6: Added verifier tests to check whether verifier rejects call 
> to bpf_map_lookup_elem from bpf program. For all map types those
> do not support map lookup.

for the set:
Acked-by: Alexei Starovoitov <ast@...nel.org>