support async operation e.g. io_uring
By io_uring, a batch of recv/send could be submitted in a single syscall; frankly it looks like sendmmsg/recvmmsg, though it is more powerful, because it can combine recv/send operations with dozens of sockets in one shot. Besides that, in order to support UDP GSO feature, multiple data shall be concatenated in a continued buffer. At present, it is possible to fetch data then feed to gnutls_record_recv(), but still hard to deal with send().
Hence could it be possible for gnutls to expose some buffer management API?