Messages in this thread | | | Date | Thu, 21 Jun 2018 16:07:19 -0700 | From | Jakub Kicinski <> | Subject | Re: [PATCH bpf-next 2/3] bpf: btf: add btf json print functionality |
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On Thu, 21 Jun 2018 15:51:17 -0700, Martin KaFai Lau wrote: > On Thu, Jun 21, 2018 at 02:59:35PM -0700, Jakub Kicinski wrote: > > On Wed, 20 Jun 2018 13:30:53 -0700, Okash Khawaja wrote: > > > $ sudo bpftool map dump -p id 14 > > > [{ > > > "key": 0 > > > },{ > > > "value": { > > > "m": 1, > > > "n": 2, > > > "o": "c", > > > "p": [15,16,17,18,15,16,17,18 > > > ], > > > "q": [[25,26,27,28,25,26,27,28 > > > ],[35,36,37,38,35,36,37,38 > > > ],[45,46,47,48,45,46,47,48 > > > ],[55,56,57,58,55,56,57,58 > > > ] > > > ], > > > "r": 1, > > > "s": 0x7ffff6f70568, > > > "t": { > > > "x": 5, > > > "y": 10 > > > }, > > > "u": 100, > > > "v": 20, > > > "w1": 0x7, > > > "w2": 0x3 > > > } > > > } > > > ] > > > > I don't think this format is okay, JSON output is an API you shouldn't > > break. You can change the non-JSON output whatever way you like, but > > JSON must remain backwards compatible. > > > > The dump today has object per entry, e.g.: > > > > { > > "key":["0x00","0x00","0x00","0x00", > > ], > > "value": ["0x02","0x00","0x00","0x00","0x00","0x00","0x00","0x00" > > ] > > } > > > > This format must remain, you may only augment it with new fields. E.g.: > > > > { > > "key":["0x00","0x00","0x00","0x00", > > ], > > "key_struct":{ > > "index":0 > > }, > > "value": ["0x02","0x00","0x00","0x00","0x00","0x00","0x00","0x00" > > ], > > "value_struct":{ > > "src_ip":2, > > "dst_ip:0 > > } > > } > I am not sure how useful to have both "key|value" and "(key|value)_struct" > while most people would prefer "key_struct"/"value_struct" if it is > available.
Agreed, it's not that useful, especially with the string-hex debacle :( It's just about the backwards compat.
> How about introducing a new option, like "-b", to print the > map with BTF (if available) such that it won't break the existing > one (-j or -p) while the "-b" output can keep using the "key" > and "value". > > The existing json can be kept as is.
That was my knee jerk reaction too, but on reflection it doesn't sound that great. We expect people with new-enough bpftool to use btf, so it should be available in the default output, without hiding it behind a switch. We could add a switch to hide the old output, but that doesn't give us back the names... What about Key and Value or k and v? Or key_fields and value_fields?
> > The name XYZ_struct may not be the best, perhaps you can come up with a > > better one? > > > > Does that make sense? Am I missing what you're doing here? > > > > One process note - please make sure you run checkpatch.pl --strict on > > bpftool patches before posting. > > > > Thanks for working on this!
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