Hi Jens,
I've been trying to use io_uring to flood a network link with UDP
packets. Essentially, the program just pushes a series of sendmsg()
calls through the SQE ring and keeps topping it up with new calls as
soon as the completions come in.
When the sendmsg() calls complete immediately then everything works
fine; however, when the calls 'block' and get queued up in the kernel
then the calls return either errno 97 or 22 when they're retried through
the workqueue (effectively, bad address or invalid iovec length).
My gut-feeling is that there's some issue copying the msghdr struct so
that the call that's retried isn't exactly the same one that was
requested. I looked into the kernel code a bit, but couldn't really
make heads or tails of it so I though I'd ask for some input while I
keep investigating.
I noticed that liburing has a simple test for sendmsg that sends a
single message; the 'punted' case doesn't seem to be tested. Is this
something you've tried?
Tested on kernels 5.3 to 5.6-pre and the behaviour's pretty much the
same with regards to the above.
Any help greatly appreciated.
Best regards,
Jonas
