GNUTLS takes a paranoid approach when seeing 0 bytes returned by the
underlying OS read() function. It will consider this an error and
return GNUTLS_E_PREMATURE_TERMINATION instead of propagating the 0
return value. It expects apps to arrange for clean termination at
the protocol level and not rely on seeing EOF from a read call to
detect shutdown. This is to harden apps against a malicious 3rd party
causing termination of the sockets layer.
This is unhelpful for the QEMU NBD code which does have a clean
protocol level shutdown, but still relies on seeing 0 from the I/O
channel read in the coroutine handling incoming replies.
The upshot is that when using a plain NBD connection shutdown is
silent, but when using TLS, the client spams the console with
Cannot read from TLS channel: Broken pipe
The NBD connection has, however, called qio_channel_shutdown()
at this point to indicate that it is done with I/O. This gives
the opportunity to optimize the code such that when the channel
has been shutdown in the read direction, the error code
GNUTLS_E_PREMATURE_TERMINATION gets turned into a '0' return
instead of an error.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20181119134228.11031-1-berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Firstly, introduce an internal qio_channel_add_watch_full(), which
enhances qio_channel_add_watch() that context can be specified.
Then add a new API wrapper qio_channel_add_watch_source() to return a
GSource pointer rather than a tag ID.
Note that the _source() call will keep a reference of GSource so that
callers need to unref them explicitly when finished using the GSource.
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Some callers want to distinguish between clean EOF (no bytes read)
vs. a short read (at least one byte read, but EOF encountered
before reaching the desired length), as it allows clients the
ability to do a graceful shutdown when a server shuts down at
defined safe points in the protocol, rather than treating all
shutdown scenarios as an error due to EOF. However, we don't want
to require all callers to have to check for early EOF. So add
another wrapper function that can be used by the callers that care
about the distinction.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170905191114.5959-3-eblake@redhat.com>
Acked-by: Daniel P. Berrange <berrange@redhat.com>
These functions wait until they are able to read / write the full
requested data buffer(s).
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Support separate coroutines for reading and writing, and place the
read/write handlers on the AioContext that the QIOChannel is registered
with.
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20170213135235.12274-7-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This is in preparation for making qio_channel_yield work on
AioContexts other than the main one.
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20170213135235.12274-6-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The GSource object has ability to have a name, which is useful
when debugging performance problems with the mainloop event
callbacks that take too long. By associating a name with a
QIOChannel object, we can then set the name on any GSource
associated with the channel.
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Testing QIOChannel feature support can be done with a helper called
qio_channel_has_feature(). Setting feature support, however, was
done manually with a logical OR. This patch introduces a new helper
called qio_channel_set_feature() and makes use of it where applicable.
Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
When QIOChannels were introduced in 666a3af9, the feature bits were
already defined shifted. However, when using them, the code was shifting
them again. The incorrect use was consistent until 74b6ce43, where
QIO_CHANNEL_FEATURE_LISTEN was defined shifted but tested unshifted.
This patch changes the definition to be unshifted and fixes the
incorrect usage introduced on 74b6ce43.
Signed-off-by: Felipe Franciosi <felipe@nutanix.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
On Win32 we cannot directly poll on socket handles. Instead we
create a Win32 event object and associate the socket handle with
the event. When the event signals readyness we then have to
use select to determine which events are ready. Creating Win32
events is moderately heavyweight, so we don't want todo it
every time we create a GSource, so this associates a single
event with a QIOChannel.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Clean up includes so that osdep.h is included first and headers
which it implies are not included manually.
This commit was created with scripts/clean-includes.
NB: If this commit breaks compilation for your out-of-tree
patchseries or fork, then you need to make sure you add
#include "qemu/osdep.h" to any new .c files that you have.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Start the new generic I/O channel framework by defining a
QIOChannel abstract base class. This is designed to feel
similar to GLib's GIOChannel, but with the addition of
support for using iovecs, qemu error reporting, file
descriptor passing, coroutine integration and use of
the QOM framework for easier sub-classing.
The intention is that anywhere in QEMU that almost
anywhere that deals with sockets will use this new I/O
infrastructure, so that it becomes trivial to then layer
in support for TLS encryption. This will at least include
the VNC server, char device backend and migration code.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
