io: some fixes to handling of /dev/null when running commands

The /dev/null file handle was leaked in a couple of places.
There is also the possibility that both readfd and writefd
point to the same

io: some fixes to handling of /dev/null when running commands

The /dev/null file handle was leaked in a couple of places.
There is also the possibility that both readfd and writefd
point to the same /dev/null file handle, so care must be
taken not to close the same file handle twice.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: increment counter when killing off subcommand

When killing the subcommand, it is intended to first send
SIGTERM, then SIGKILL and only report an error if it still
doesn't die after SIGKILL. The

io: increment counter when killing off subcommand

When killing the subcommand, it is intended to first send
SIGTERM, then SIGKILL and only report an error if it still
doesn't die after SIGKILL. The 'step' counter was not
being incremented though, so the code never got past the
SIGTERM stage.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: fix sign of errno value passed to error report

When reporting the number of FDs has been exceeded, pass
EINVAL to error_setg_errno, rather than -EINVAL.

Signed-off-by: Daniel P. Berrange <berra

io: fix sign of errno value passed to error report

When reporting the number of FDs has been exceeded, pass
EINVAL to error_setg_errno, rather than -EINVAL.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: fix stack allocation when sending of file descriptors

When sending file descriptors over a socket, we have to
allocate a data buffer to hold the FDs in the scmsghdr.
Unfortunately we allocated t

io: fix stack allocation when sending of file descriptors

When sending file descriptors over a socket, we have to
allocate a data buffer to hold the FDs in the scmsghdr.
Unfortunately we allocated the buffer on the stack inside
an if () {} block, but called sendmsg() outside the block.
So the stack bytes holding the FDs were liable to be
overwritten with other data. By luck this was not a problem
when sending 1 FD, but if sending 2 or more then it would
fail.

The fix is to simply move the variables outside the nested
'if' block. To keep valgrind quiet we also zero-initialize
the 'control' buffer.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: fix setting of QIO_CHANNEL_FEATURE_FD_PASS on server connections

The QIO_CHANNEL_FEATURE_FD_PASS feature flag is set in the
qio_channel_socket_set_fd() method, however, this only deals
with clie

io: fix setting of QIO_CHANNEL_FEATURE_FD_PASS on server connections

The QIO_CHANNEL_FEATURE_FD_PASS feature flag is set in the
qio_channel_socket_set_fd() method, however, this only deals
with client side connections.

To ensure server side connections also have the feature flag
set, we must set it in qio_channel_socket_accept() too. This
also highlighted a typo fix where the code updated the
sockaddr struct in the wrong object instance.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add QIOChannelBuffer class

Add a QIOChannel subclass that is capable of performing I/O
to/from a memory buffer. This implementation does not attempt
to support concurrent readers & writers. It i

io: add QIOChannelBuffer class

Add a QIOChannel subclass that is capable of performing I/O
to/from a memory buffer. This implementation does not attempt
to support concurrent readers & writers. It is designed for
serialized access where by a single thread at a time may write
data, seek and then read data back out.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add QIOChannelCommand class

Add a QIOChannel subclass that is capable of performing I/O
to/from a separate process, via a pair of pipes. The command
can be used for unidirectional or bi-directio

io: add QIOChannelCommand class

Add a QIOChannel subclass that is capable of performing I/O
to/from a separate process, via a pair of pipes. The command
can be used for unidirectional or bi-directional I/O.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add QIOChannelWebsock class

Add a QIOChannel subclass that can run the websocket protocol over
the top of another QIOChannel instance. This initial implementation
is only capable of acting as a

io: add QIOChannelWebsock class

Add a QIOChannel subclass that can run the websocket protocol over
the top of another QIOChannel instance. This initial implementation
is only capable of acting as a websockets server. There is no support
for acting as a websockets client yet.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add QIOChannelTLS class

Add a QIOChannel subclass that can run the TLS protocol over
the top of another QIOChannel instance. The object provides a
simplified API to perform the handshake when st

io: add QIOChannelTLS class

Add a QIOChannel subclass that can run the TLS protocol over
the top of another QIOChannel instance. The object provides a
simplified API to perform the handshake when starting the TLS
session. The layering of TLS over the underlying channel does
not have to be setup immediately. It is possible to take an
existing QIOChannel that has done some handshake and then swap
in the QIOChannelTLS layer. This allows for use with protocols
which start TLS right away, and those which start plain text
and then negotiate TLS.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add QIOChannelFile class

Add a QIOChannel subclass that is capable of operating on things
that are files, such as plain files, pipes, character/block
devices, but notably not sockets.

Signed-of

io: add QIOChannelFile class

Add a QIOChannel subclass that is capable of operating on things
that are files, such as plain files, pipes, character/block
devices, but notably not sockets.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add QIOChannelSocket class

Implement a QIOChannel subclass that supports sockets I/O.
The implementation is able to manage a single socket file
descriptor, whether a TCP/UNIX listener, TCP/UNIX

io: add QIOChannelSocket class

Implement a QIOChannel subclass that supports sockets I/O.
The implementation is able to manage a single socket file
descriptor, whether a TCP/UNIX listener, TCP/UNIX connection,
or a UDP datagram. It provides APIs which can listen and
connect either asynchronously or synchronously. Since there
is no asynchronous DNS lookup API available, it uses the
QIOTask helper for spawning a background thread to ensure
non-blocking operation.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add QIOTask class for async operations

A number of I/O operations need to be performed asynchronously
to avoid blocking the main loop. The caller of such APIs need
to provide a callback to be in

io: add QIOTask class for async operations

A number of I/O operations need to be performed asynchronously
to avoid blocking the main loop. The caller of such APIs need
to provide a callback to be invoked on completion/error and
need access to the error, if any. The small QIOTask provides
a simple framework for dealing with such probes. The API
docs inline provide an outline of how this is to be used.

Some functions don't have the ability to run asynchronously
(eg getaddrinfo always blocks), so to facilitate their use,
the task class provides a mechanism to run a blocking
function in a thread, while triggering the completion
callback in the main event loop thread. This easily allows
any synchronous function to be made asynchronous, albeit
at the cost of spawning a thread.

In this series, the QIOTask class will be used for things like
the TLS handshake, the websockets handshake and TCP connect()
progress.

The concept of QIOTask is inspired by the GAsyncResult
interface / GTask class in the GIO libraries. The min
version requirements on glib don't allow those to be
used from QEMU, so QIOTask provides a facsimilie which
can be easily switched to GTask in the future if the
min version is increased.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add helper module for creating watches on FDs

A number of the channel implementations will require the
ability to create watches on file descriptors / sockets.
To avoid duplicating this code in

io: add helper module for creating watches on FDs

A number of the channel implementations will require the
ability to create watches on file descriptors / sockets.
To avoid duplicating this code in each channel, provide a
helper API for dealing with file descriptor watches.

There are two watch implementations provided. The first
is useful for bi-directional file descriptors such as
sockets, regular files, character devices, etc. The
second works with a pair of unidirectional file descriptors
such as pipes.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

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io: add abstract QIOChannel classes

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 addi

io: add abstract QIOChannel classes

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>

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