Re: 9p/RDMA for syzkaller (Was: BUG: corrupted list in p9_read_work)

[Dominique Martinet <asmadeus@codewreck.org>]

Dmitry Vyukov wrote on Tue, Nov 20, 2018:
> I don't understand most of the words here, so I probably won't be of help.
> 
> Leon told me that there is some kind of software emulation RDMA
> interface (CONFIG_RDMA_RXE?). Maybe it can be used to create an
> emulated RDMA interface per test process and use it to communicate
> with 9p client?

Yes, rxe is what you made me look into and is what I was talking about
here - the problem is I can't seem to figure how to use it *as udp*
within a single machine.

With two VMs or a remote outside of the VM when I try to open a RDMA
connection with that software emulation I get nicely understandable udp
packets ; but within a single VM there is nothing visible at the udp
layer, even if I explicitely configure multiple interfaces and try to
use one as rxe and another without it that would act as "outside" -- the
kernel doesn't send anything to the normal interface like it normally
would.

There might be other ways around it (I'm starting to think very ugly
things like really pretend to connect to an IP outside of the VM, but
capture the outgoing traffic with pcap and forge the replies), but I'd
rather not have to go to this extent...

-- 
Dominique