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[Qemu-devel] [RFC][PATCH 00/15] virtproxy: host/guest communication laye
From: |
Michael Roth |
Subject: |
[Qemu-devel] [RFC][PATCH 00/15] virtproxy: host/guest communication layer |
Date: |
Fri, 22 Oct 2010 13:43:16 -0500 |
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.
Currently this communication involves 2 daemons (common code): 1 in the guest,
and 1 in the host. Each end multiplexes/demultiplexes/proxies connections from
the other end. In the future we hope to integrate the host component directly
into qemu as a chardev.
BUILD/USAGE INFO:
make qemu-vp
./qemu-vp -h
EXAMPLE USAGE:
- 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 socket,path=/tmp/test0-virtioconsole.sock,server,nowait,id=test0 \
-device virtconsole,chardev=test0,name=test0 \
-chardev socket,path=/tmp/test1-virtio-serial.sock,server,nowait,id=test1 \
-device virtserialport,chardev=test1,name=test1 \
-chardev socket,path=/tmp/test2-virtio-serial.sock,server,nowait,id=test2 \
-device virtserialport,chardev=test2,name=test2 \
...
# in the host:
./qemu-vp -c unix-connect:/tmp/test2-virtio-serial.sock:- -o
http:127.0.0.1:9080 \
-o ssh:127.0.0.1:9022
# 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
- Proxy http and ssh connections from a host to a guest over a network
connection:
# start guest with network connectivity to host
# in the guest:
./qemu-vp -c tcp-listen:<guest_ip>:9000 -i http:127.0.0.1:80 \
-i ssh:127.0.0.1:22
# in the host:
./qemu-vp -c tcp-connect:<guest_ip>:9000 -o http:127.0.0.1:9080 \
-o ssh:127.0.0.1:9022
...
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:
- Deadlocking the guest: In tests over isa-serial ports I've hit cases where
the chardev (socket) on the host-side seem to fill up the buffer, likely due to
qemu rate-limiting data in accordance with the port's baud rate (which may
explain why i hadn't seen this with network-based or virtio-serial data
channels. When qemu-vp reads data from client connections it puts it into a
VPPacket and tries to send the packet in it's entirety back over the channel.
In this particular case that write() blocks (or vp_send_all() spins if we set
O_NONBLOCK on the client FD). In the meantime qemu fills up the other end of
the socket buffer and ends up spinning in qemu-char:send_all(), basically
causing a deadlock between qemu and qemu-vp, and causing the guest to freeze.
Currently I'm planning on replacing vp_send_all() with a function that
simply buffers write()'s, which would allow the use of non-blocking write()'s
out to the channel/chardev socket while still retaining wholeness/fifo-ordering
of the VPPackets.
- 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.
TODO:
- Rework vp_send_all() to use buffering to avoid above-mentioned deadlock
scenario
- Integrate qemu-vp directly into qemu by adding a virtproxy chardev device.
For example:
./qemu-vp -c unix-connect:/tmp/vp1-virtio-serial.sock:- -o
ssh:127.0.0.1:9022
in the host, would be analogous to:
qemu \
-device virtio-serial \
-chardev virtproxy,oforward=ssh:127.0.0.1:9022,id=vp1 \
-device virtserialport,chardev=vp1,name=vp1
- Better channel negotiation to gracefully handle guest reboots/disconnects/etc
- Add monitor commands to add/remove virtproxy channels/oforwards/iforwards on
the fly
.gitignore | 1 +
Makefile | 4 +-
configure | 1 +
qemu-vp.c | 618 +++++++++++++++++++++++++++++++++++++++++++++
virtproxy.c | 799 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
virtproxy.h | 40 +++
6 files changed, 1462 insertions(+), 1 deletions(-)
- [Qemu-devel] [RFC][PATCH 00/15] virtproxy: host/guest communication layer,
Michael Roth <=
- [Qemu-devel] [RFC][PATCH 06/15] virtproxy: add read handler for communication channel, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 02/15] virtproxy: qemu-vp, standalone daemon skeleton, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 07/15] virtproxy: add vp_new() VPDriver constructor, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 03/15] virtproxy: add debug functions for virtproxy core, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 08/15] virtproxy: interfaces to set/remove/handle VPOForwards, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 09/15] virtproxy: add handler for data packets, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 10/15] virtproxy: add handler for control packet, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 11/15] virtproxy: add vp_handle_packet(), Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 12/15] virtproxy: interfaces to set/remove VPIForwards, Michael Roth, 2010/10/22
- [Qemu-devel] [RFC][PATCH 01/15] virtproxy: base data structures and constants, Michael Roth, 2010/10/22