04/02/2020 10:19, Ferruh Yigit: > On 2/3/2020 6:40 PM, Thomas Monjalon wrote: > > 03/02/2020 18:40, Ferruh Yigit: > >> On 2/3/2020 5:09 PM, Thomas Monjalon wrote: > >>> 03/02/2020 10:30, Ferruh Yigit: > >>>> On 2/2/2020 2:41 PM, Ananyev, Konstantin wrote: > >>>>> 02/02/2020 14:05, Thomas Monjalon: > >>>>>> 31/01/2020 15:16, Trahe, Fiona: > >>>>>>> On 1/30/2020 8:18 PM, Thomas Monjalon wrote: > >>>>>>>> 30/01/2020 17:09, Ferruh Yigit: > >>>>>>>>> On 1/29/2020 8:13 PM, Akhil Goyal wrote: > >>>>>>>>>> > >>>>>>>>>> I believe these enums will be used only in case of ASYM case which > >>>>>>>>>> is experimental. > >>>>>>>>> > >>>>>>>>> Independent from being experiment and not, this shouldn't be a > >>>>>>>>> problem, I think > >>>>>>>>> this is a false positive. > >>>>>>>>> > >>>>>>>>> The ABI break can happen when a struct has been shared between the > >>>>>>>>> application > >>>>>>>>> and the library (DPDK) and the layout of that memory know > >>>>>>>>> differently by > >>>>>>>>> application and the library. > >>>>>>>>> > >>>>>>>>> Here in all cases, there is no layout/size change. > >>>>>>>>> > >>>>>>>>> As to the value changes of the enums, since application compiled > >>>>>>>>> with old DPDK, > >>>>>>>>> it will know only up to '6', 7 and more means invalid to the > >>>>>>>>> application. So it > >>>>>>>>> won't send these values also it should ignore these values from > >>>>>>>>> library. Only > >>>>>>>>> consequence is old application won't able to use new features those > >>>>>>>>> new enums > >>>>>>>>> provide but that is expected/normal. > >>>>>>>> > >>>>>>>> If library give higher value than expected by the application, > >>>>>>>> if the application uses this value as array index, > >>>>>>>> there can be an access out of bounds. > >>>>>>> > >>>>>>> [Fiona] All asymmetric APIs are experimental so above shouldn't be a > >>>>>>> problem. > >>>>>>> But for the same issue with sym crypto below, I believe Ferruh's > >>>>>>> explanation makes > >>>>>>> sense and I don't see how there can be an API breakage. > >>>>>>> So if an application hasn't compiled against the new lib it will be > >>>>>>> still using the old value > >>>>>>> which will be within bounds. If it's picking up the higher new value > >>>>>>> from the lib it must > >>>>>>> have been compiled against the lib so shouldn't have problems. > >>>>>> > >>>>>> You say there is no ABI issue because the application will be > >>>>>> re-compiled > >>>>>> for the updated library. Indeed, compilation fixes compatibility > >>>>>> issues. > >>>>>> But this is not relevant for ABI compatibility. > >>>>>> ABI compatibility means we can upgrade the library without recompiling > >>>>>> the application and it must work. > >>>>>> You think it is a false positive because you assume the application > >>>>>> "picks" the new value. I think you miss the case where the new value > >>>>>> is returned by a function in the upgraded library. > >>>>>> > >>>>>>> There are also no structs on the API which contain arrays using this > >>>>>>> for sizing, so I don't see an opportunity for an appl to have a > >>>>>>> mismatch in memory addresses. > >>>>>> > >>>>>> Let me demonstrate where the API may "use" the new value > >>>>>> RTE_CRYPTO_AEAD_CHACHA20_POLY1305 and how it impacts the application. > >>>>>> > >>>>>> Once upon a time a DPDK application counting the number of devices > >>>>>> supporting each AEAD algo (in order to find the best supported algo). > >>>>>> It is done in an array indexed by algo id: > >>>>>> int aead_dev_count[RTE_CRYPTO_AEAD_LIST_END]; > >>>>>> The application is compiled with DPDK 19.11, > >>>>>> where RTE_CRYPTO_AEAD_LIST_END = 3. > >>>>>> So the size of the application array aead_dev_count is 3. > >>>>>> This binary is run with DPDK 20.02, > >>>>>> where RTE_CRYPTO_AEAD_CHACHA20_POLY1305 = 3. > >>>>>> When calling rte_cryptodev_info_get() on a device QAT_GEN3, > >>>>>> rte_cryptodev_info.capabilities.sym.aead.algo is set to > >>>>>> RTE_CRYPTO_AEAD_CHACHA20_POLY1305 (= 3). > >>>>>> The application uses this value: > >>>>>> ++ aead_dev_count[info.capabilities.sym.aead.algo]; > >>>>>> The application is crashing because of out of bound access. > >>>>> > >>>>> I'd say this is an example of bad written app. > >>>>> It probably should check that returned by library value doesn't > >>>>> exceed its internal array size. > >>>> > >>>> +1 > >>>> > >>>> Application should ignore values >= MAX. > >>> > >>> Of course, blaming the API user is a lot easier than looking at the API. > >>> Here the API has RTE_CRYPTO_AEAD_LIST_END which can be understood > >>> as the max value for the application. > >>> Value ranges are part of the ABI compatibility contract. > >>> It seems you expect the application developer to be aware that > >>> DPDK could return a higher value, so the application should > >>> check every enum values after calling an API. CRAZY. > >>> > >>> When we decide to announce an ABI compatibility and do some marketing, > >>> everyone is OK. But when we need to really make our ABI compatible, > >>> I see little or no effort. DISAPPOINTING. > >> > >> This is not to blame the user or to do less work, this is more sane > >> approach > >> that library provides the _END/_MAX value and application uses it as valid > >> range > >> check. > >> > >>>> Do you suggest we don't extend any enum or define between ABI breakage > >>>> releases > >>>> to be sure bad written applications not affected? > >>> > >>> I suggest we must consider not breaking any assumption made on the API. > >>> Here we are breaking the enum range because nothing mentions _LIST_END > >>> is not really the absolute end of the enum. > >>> The solution is to make the change below in 20.02 + backport in 19.11.1: > >>> > >>> - _LIST_END > >>> + _LIST_END, /* an ABI-compatible version may increase this value */ > >>> + _LIST_MAX = _LIST_END + 42 /* room for ABI-compatible additions */ > >>> }; > >>> > >> > >> What is the point of "_LIST_MAX" here? > > > > _LIST_MAX is range of value that DPDK can return in the ABI contract. > > So the appplication can rely on the range 0.._LIST_MAX. > > > >> Application should know the "_LIST_END" of when it has been compiled for > >> the > >> valid range check. Next time it is compiled "_LIST_END" may be different > >> value > >> but same logic applies. > > > > No, ABI compatibility contract means you can compile your application > > with DPDK 19.11.0 and run it with DPDK 20.02. > > So _LIST_END comes from 19.11 and does not include ChachaPoly. > > That is what I mean, let me try to give a sample. > > DPDK19.11 returns, A=1, B=2, END=3 > > Application compiled with DPDK19.11, it will process A, B and ignore anything > ">= 3"
No, the application will not ignore anything ">=3" as I explained above, and you blamed the application for it. Nothing in the API says the application must filter value higher than 3, because as of now, values higher than 3 are PMD bug. > DPDK20.02 returns A=1, B=2, C=3, D=4, END=5 > > Old application will still only will know/use A, B and can ignore when library > sends C=3, D=4 etc... > > > In above, if you add another limit as you suggested, like MAX=10 and ask > application to use it, > > Application compiled with DPDK19.11 will be OK since library only sends A,B > and > application uses them. > > But with DPDK20.02 application may have problem, since library will be sending > C=3, which is valid according to the check " <= MAX (10)", how application > will > know to ignore it. Why application should ignore value C=3 with DPDK 20.02? > So application should use _END to know the valid ones according it, if so what > is the point of having _MAX. > > > >> When "_LIST_END" is missing, application can't protect itself, in that case > >> library should send only the values application knows when it is compiled, > >> this > >> means either we can't extend our enum/defines until next ABI breakage, or > >> we > >> need to do ABI versioning to the functions that returns an enum each time > >> enum > >> value extended. > > > > If we define _LIST_MAX as a bigger value than current _LIST_END, > > we have some room to add values in between. > > > > If (as of now) we don't have _LIST_MAX room, then yes we must version > > the functions returning the enum. > > In this case, the proper solution is to implement > > rte_cryptodev_info_get_v1911() so it filters out > > RTE_CRYPTO_AEAD_CHACHA20_POLY1305 capability. > > With this solution, an application compiled with DPDK 19.11 will keep > > seeing the same range as before, while a 20.02 application could > > see and use ChachaPoly. > > This is another proposal that I was expecting from the crypto team, > > instead of claiming there is no issue (and wasting precious time). > > > > > >> I believe it is saner to provide _END/_MAX values to the application to > >> use. And > >> if required comment them to clarify the expected usage. > >> > >> But in above suggestion application can't use or rely on "_LIST_MAX", it > >> doesn't > >> mean anything to application. > > > > I don't understand what you mean. I think you misunderstood what is ABI > > compat. > > > > > >>> Then *_LIST_END values could be ignored by libabigail with such a change. > >>> > >>> If such a patch is not done by tomorrow, I will have to revert > >>> Chacha-Poly commits before 20.02-rc2, because > >>> > >>> 1/ LIST_END, without any comment, means "size of range" > >>> 2/ we do not blame users for undocumented ABI changes > >>> 3/ we respect the ABI compatibility contract
