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

Jens Axboe
2022-03-23T20:15:13Z

On 3/23/22 2:13 PM, Pavel Begunkov 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.

Yes was thinking that too, nothing is final yet.. Need to write a
SOCK_STREAM test case.

--
Jens Axboe