Does every error returned by DeviceIoControl() correspond to a
transport error (with the meaning that I explained earlier)?
nl_sock_transact_multiple__() should report that are not transport
errors by constructing a nlmsghdr reply with an mlmsgerr as its
payload.
Here is the high level situation. With a Linux kernel, it is more
efficient to send multiple Netlink requests to the kernel in a batch
using a single system call. The results are equivalent to sending the
requests one-by-one. As an optimization, if there is a severe error
that means that no requests are going to succeed at all, then the code
may skip sending the remaining requests. That is the only case that
this is meant to handle:
} else if (error) {
VLOG_ERR_RL(&rl, "transaction error (%s)", ovs_strerror(error));
nl_sock_record_errors__(transactions, n, error);
}
This code will *not* handle ordinary errors short of this kind of
severe error properly, and should not be invoked in that case. (It is
also buggy in that case, and I see that the patch fixes that bug, but
that is not my point here.) If in fact on Windows it is getting
invoked in cases other than a severe error, then
nl_sock_record_errors__() should be modified to report ordinary errors
differently (probably by constructing an nlmsghdr+nlmsgerr).
Thanks,
Ben.
On Tue, Apr 14, 2015 at 09:19:10PM +0000, Alin Serdean wrote:
> In nl_sock_transact_multiple__ we do the following:
>
> if (!DeviceIoControl(sock->handle, OVS_IOCTL_TRANSACT,
> txn->request->data,
> txn->request->size,
> reply_buf, sizeof reply_buf,
> &reply_len, NULL)) {
> /* XXX: Map to a more appropriate error. */
> error = EINVAL;
> break;
> }
>
> We map every failure to EINVAL that is why it did not pop out into Linux.
>
> We should definitely log the error using ovs_lasterror_to_string before
> setting it to EINVAL.
>
> Maybe we should just increase the number of transactions in some
> situations(i.e. STATUS_INVALID_PARAMETER) as an idea to allow the rest of the
> transactions to be processed.
>
> Alin.
> -----Mesaj original-----
> De la: dev [mailto:dev-boun...@openvswitch.org] ??n numele Ben Pfaff
> Trimis: Tuesday, April 14, 2015 11:42 PM
> C??tre: Sorin Vinturis
> Cc: dev@openvswitch.org
> Subiect: Re: [ovs-dev] [PATCH] netlink-socket: Exit NL transaction loop when
> EINVAL is returned
>
> On Tue, Apr 14, 2015 at 08:25:59PM +0000, Sorin Vinturis wrote:
> > The nl_sock_transact_multiple function enters in an infinite loop,
> > when invalid error, EINVAL, is returned by nl_sock_transact_multiple__.
> > EINVAL is the error returned by the latter function when a driver
> > request fails.
> >
> > Signed-off-by: Sorin Vinturis <svintu...@cloudbasesolutions.com>
> > Reported-by: Alin Gabriel Serdean <aserd...@cloudbasesolutions.com>
> > Reported-at: https://github.com/openvswitch/ovs-issues/issues/57
>
> I see that this fixes a bug, even on Linux. Thank you. It's actually a
> pretty serious bug (given the infinite loop), but I guess that it must not
> occur in any normal circumstances, otherwise we would have heard about it
> over the years.
>
> However, I want to make sure of something before I commit it.
> nl_sock_transact_multiple__() should only return an error in the case of a
> "transport" error, that is, of some problem communicating with the datapath
> (e.g. the kernel module has been removed or something similarly fatal). It
> should not return an error in cases where some message asks the datapath to
> do something erroneous (e.g. to add a flow that the datapath doesn't
> understand, to delete a vport that doesn't exist, ...). This is because only
> in the former case should all of the transactions be aborted; in the latter
> case, any remaining transactions should still be processed.
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