Re: [PATCH 1/2] io_uring: ensure recv and recvmsg handle MSG_WAITALL correctly

Pavel Begunkov
2022-03-23T20:14:27Z

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