Am Mittwoch, 24. Dezember 2014, 07:24:01 schrieb Herbert Xu: Hi Herbert, > On Tue, Dec 23, 2014 at 03:52:27PM +0100, Stephan Mueller wrote: > > Am Dienstag, 23. Dezember 2014, 22:56:26 schrieb Herbert Xu: > > > In fact AEAD is rather awkward because you need to do everything > > > in one go. Perhaps we could adapt our kernel interface to allow > > > partial AEAD operations? > > > > I am not sure what you are referring to. The invocation does not need to > > be in one go. You can have arbitrary number of sendmsg calls. But all > > input data needs to be supplied before you call recvmsg. > > What I mean is that unlike skcipher we cannot precede until we > have the complete input. So you cannot begin recvmsg until all > input has been sent. That is right, but isn't that the nature of AEAD ciphers in general? Even if you are in the kernel, you need to have all scatter lists together for one invocation of the AEAD cipher. In case of a threaded application, the recvmsg does not start until all data is in, marked with the missing MSG_MORE -- see aead_readable. All we can do is allow the user to use multiple system calls to collect all data before the AEAD operation takes place. Or do you see another way on how to invoke the AEAD operation in a different manner? The only item that I see that could be made better is the output side: currently the code allows only one and exactly one iovec to point to the output buffer. I would like to allow multiple iovec buffers that are filled with the output of one invocation of the AEAD operation. However, to avoid making a kernel-internal scratch buffer, I would need to somehow link the kernel-internal scatter lists with the iovec buffers. That only works when walking the iovec lists first and call af_alg_make_sg with every iovec entry and create the kernel-internal scatterlist representation. That is followed by the AEAD operation on the scatterlist. If we agree on walking the iovec list first, then the question arises how many iovec list entries we allow at max. Is 16 entries a sensible value? -- Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
