[Qemu-devel] [RFC][PATCH v2 00/19] virtproxy: host/guest communication layer

[Michael Roth]

OVERVIEW:

Virtproxy proxies and multiplexes socket streams over a data channel between a 
host and a guest (currently network connections, emulated serial, or 
virtio-serial channels are supported). This allows for services such as guest 
data collection agents, host/guest file transfer, and event generation/handling 
to be implemented/deployed as basic socket-based daemons, independently of the 
actual data channel.

This code is intended to provide a channel-independent abstraction layer for 
communicating with a QEMU-specific guest agent (in particular, the virtagent 
RPC guest agent which will follow this in a seperate patchset), but may have 
general utility beyond this (for instance: ssh/sftp/other guest agents/etc over 
isa/virtio serial), and so is submitted here as a seperate patchset.

CHANGES IN V2:
 - host daemon deprecated, virtproxy now integrated into qemu via a virtproxy 
chardev. The command-line options have not yet been converted over so for now 
the virtproxy layer is no longer testable directly. This will be addressed 
soon. Virtagent will hook into this chardev via a boolean chardev option. That 
patchset will follow this one shortly.
 - deadlocking issue resolved

BUILD/USAGE INFO:
  # build guest daemon
  make qemu-vp
  ./qemu-vp -h

EXAMPLE USAGE:

note: oforward/iforward chardev options have not yet been converted over from 
original standalone host daemon implementation so this won't work till then. 
The examples however have been updated for reference.

 - Proxy http and ssh connections from a host to a guest over a virtio-serial 
connection:
    # start guest with virtio-serial. for example (RHEL6s13):
    qemu \
    -device virtio-serial \
    -chardev virtproxy,id=test0, \
             oforward=http:127.0.0.1:9080,oforward=ssh:127.0.0.1:22 \
    -device virtconsole,chardev=test0,name=test0 \
    ...
    # in the guest:
    ./qemu-vp -c virtserial-open:/dev/virtio-ports/test2:- -i http:127.0.0.1:80 
\
              -i ssh:127.0.0.1:22

    # from host, access guest http server
    wget http://locahost:9080
    # from host, access guest ssh server
    ssh localhost -p 9022

By specifying -i and -o options in the host and guest, respectively, the 
channel can also be used to establish connections from a guest to a host.

KNOWN ISSUES:

 - Sync issues with virtio-serial: This may or may not be related to the issue 
above, but I noticed some cases where proxied ssh sessions from the guest to 
the host would "lag" by a few bytes. For instance typing "top" would result in 
"to" being displayed, and the "p" wouldn't show up till I hit another key. This 
could be related to how I'm handling the buffering, but I haven't been able to 
reproduce using a network-based channel. UPDATE: this issue seems to be fixed 
here:

    
http://git.kernel.org/?p=linux/kernel/git/rusty/linux-2.6-for-linus.git;a=commit;h=6df7aadcd9290807c464675098b5dd2dc9da5075

TODO:

 - Better channel negotiation to gracefully handle guest reboots/disconnects/etc
 - Port qemu-vp -i/-o options to chardev options
 - Add monitor commands to add/remove virtproxy channels/oforwards/iforwards on 
the fly

 .gitignore          |    1 +
 Makefile            |    4 +-
 Makefile.target     |    2 +-
 configure           |    1 +
 qemu-char.c         |   43 +++
 qemu-vp.c           |  624 +++++++++++++++++++++++++++++++++++++
 roms/seabios        |    2 +-
 virtproxy-builtin.c |   38 +++
 virtproxy.c         |  863 +++++++++++++++++++++++++++++++++++++++++++++++++++
 virtproxy.h         |   47 +++
 10 files changed, 1622 insertions(+), 3 deletions(-)