On Wed, Mar 23, 2022 at 10:14 PM Pavel Begunkov <asml.silence@xxxxxxxxx> wrote: > > On 3/23/22 15:39, Jens Axboe wrote: > > We currently don't attempt to get the full asked for length even if > > MSG_WAITALL is set, if we get a partial receive. If we do see a partial > > receive, then just note how many bytes we did and return -EAGAIN to > > get it retried. > > > > The iov is advanced appropriately for the vector based case, and we > > manually bump the buffer and remainder for the non-vector case. > > How datagrams work with MSG_WAITALL? I highly doubt it coalesces 2+ > packets to satisfy the length requirement (e.g. because it may move > the address back into the userspace). I'm mainly afraid about > breaking io_uring users who are using the flag just to fail links > when there is not enough data in a packet. > > -- > Pavel Begunkov Pavel: Datagrams have message boundaries and the MSG_WAITALL flag does not make sense there. I believe it is ignored by receive code on daragram sockets. MSG_WAITALL makes sends only on stream sockets, like TCP. The manual page says "This flag has no effect for datagram sockets.". -- ---------------------------------------- Constantine Gavrilov Storage Architect Master Inventor Tel-Aviv IBM Storage Lab 1 Azrieli Center, Tel-Aviv ----------------------------------------
