Re: [PATCH V8 1/6] qapi/net: Add IPFlowSpec and QMP command for COLO passthrough

[Dr. David Alan Gilbert]

* Markus Armbruster (armbru@redhat.com) wrote:
> Zhang Chen <chen.zhang@intel.com> writes:
> 
> > Since the real user scenario does not need COLO to monitor all traffic.
> > Add colo-passthrough-add and colo-passthrough-del to maintain
> > a COLO network passthrough list. Add IPFlowSpec struct for all QMP commands.
> > All the fields of IPFlowSpec are optional.
> >
> > Signed-off-by: Zhang Chen <chen.zhang@intel.com>
> > ---
> 
> The QAPI schema looks good to me, but the interface documentation is
> still not quite clear enough.  To make progress, I'm going to make
> concrete suggestions wherever I can despite being quite clueless about
> the subject matter.  Risks me writing something that's clearer, but
> wrong.  Keep that in mind, please.
> 
> >  net/net.c     | 10 +++++++
> >  qapi/net.json | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 84 insertions(+)
> >
> > diff --git a/net/net.c b/net/net.c
> > index 76bbb7c31b..f913e97983 100644
> > --- a/net/net.c
> > +++ b/net/net.c
> > @@ -1195,6 +1195,16 @@ void qmp_netdev_del(const char *id, Error **errp)
> >      }
> >  }
> >  
> > +void qmp_colo_passthrough_add(IPFlowSpec *spec, Error **errp)
> > +{
> > +    /* TODO implement setup passthrough rule */
> > +}
> > +
> > +void qmp_colo_passthrough_del(IPFlowSpec *spec, Error **errp)
> > +{
> > +    /* TODO implement delete passthrough rule */
> > +}
> > +
> >  static void netfilter_print_info(Monitor *mon, NetFilterState *nf)
> >  {
> >      char *str;
> > diff --git a/qapi/net.json b/qapi/net.json
> > index 7fab2e7cd8..91f2e1495a 100644
> > --- a/qapi/net.json
> > +++ b/qapi/net.json
> > @@ -7,6 +7,7 @@
> >  ##
> >  
> >  { 'include': 'common.json' }
> > +{ 'include': 'sockets.json' }
> >  
> >  ##
> >  # @set_link:
> > @@ -696,3 +697,76 @@
> >  ##
> >  { 'event': 'FAILOVER_NEGOTIATED',
> >    'data': {'device-id': 'str'} }
> > +
> > +##
> > +# @IPFlowSpec:
> > +#
> > +# IP flow specification.
> > +#
> > +# @protocol: Transport layer protocol like TCP/UDP, etc. The protocol is 
> > the
> > +#            string instead of enum, because it can be passed to 
> > getprotobyname(3)
> > +#            and avoid duplication with /etc/protocols.
> 
> The rationale is good, but it doesn't really belong into the interface
> documentation.  Suggest:
> 
>    # @protocol: Transport layer protocol like TCP/UDP, etc.  This will be
>    #            passed to getprotobyname(3).
> 
> 
> > +#
> > +# @object-name: The @object-name means packet handler in Qemu. Because not
> > +#               all the network packet must pass the colo-compare module,
> > +#               the net-filters are same situation. There modules attach to
> > +#               netdev or chardev to work, VM can run multiple modules
> > +#               at the same time. So it needs the object-name to set
> > +#               the effective module.
> 
> I still don't understand this, and I'm too ignorant of COLO and
> networking to suggest improvements.
> 
> Jason or David, perhaps?

I'll leave Jason to check on the object behaviour (and I see the rest of
the thread); but at a high level, COLO is deciding whether to do VM
synchronisation on whether the network behaviour of the two VMs get out
of sync (e.g. due to randomness in the flow of requests); if you don't
sync then when you fail-over, you'll get TCP errors/inconsistencies in
the stream view from the secondary; but this patch series is saying
you don't care if some TCP connections fail like that, you only care
about maybe the main sockets the application is providing.

Dave

> > +#
> > +# @source: Source address and port.
> > +#
> > +# @destination: Destination address and port.
> > +#
> > +# Since: 6.1
> > +##
> > +{ 'struct': 'IPFlowSpec',
> > +  'data': { '*protocol': 'str', '*object-name': 'str',
> > +    '*source': 'InetSocketAddressBase',
> > +    '*destination': 'InetSocketAddressBase' } }
> > +
> > +##
> > +# @colo-passthrough-add:
> > +#
> > +# Add passthrough entry IPFlowSpec to the COLO-compare instance.
> > +# The protocol and source/destination IP/ports are optional. if the user
> > +# only inputs part of the information, this will match all traffic.
> 
> Actually, all arguments are optional.
> 
> Suggest:
> 
>    # Add an entry to the COLO network passthrough list.
>    # Absent protocol, host addresses and ports match anything.
> 
> If there is more than one such list, then "to a COLO network passthrough
> list" instead.
> 
> Still missing then: meaning of absent @object-name.  Does it select the
> COLO network passthrough list, perhaps?
> 
> > +#
> > +# Returns: Nothing on success
> > +#
> > +# Since: 6.1
> > +#
> > +# Example:
> > +#
> > +# -> { "execute": "colo-passthrough-add",
> > +#      "arguments": { "protocol": "tcp", "object-name": "object0",
> > +#      "source": {"host": "192.168.1.1", "port": "1234"},
> > +#      "destination": {"host": "192.168.1.2", "port": "4321"} } }
> > +# <- { "return": {} }
> > +#
> > +##
> > +{ 'command': 'colo-passthrough-add', 'boxed': true,
> > +     'data': 'IPFlowSpec' }
> > +
> > +##
> > +# @colo-passthrough-del:
> > +#
> > +# Delete passthrough entry IPFlowSpec to the COLO-compare instance.
> > +# The protocol and source/destination IP/ports are optional. if the user
> > +# only inputs part of the information, this will match all traffic.
> 
> I suspect this command doesn't actually match traffic, it matches
> entries added with colo-passthrough-add.
> 
> Can it delete more than one such entry?
> 
> Suggest:
> 
>    # Delete an entry from the COLO network passthrough list.
> 
> and then explain how the command arguments select entries.
> 
> > +#
> > +# Returns: Nothing on success
> > +#
> > +# Since: 6.1
> > +#
> > +# Example:
> > +#
> > +# -> { "execute": "colo-passthrough-del",
> > +#      "arguments": { "protocol": "tcp", "object-name": "object0",
> > +#      "source": {"host": "192.168.1.1", "port": "1234"},
> > +#      "destination": {"host": "192.168.1.2", "port": "4321"} } }
> > +# <- { "return": {} }
> > +#
> > +##
> > +{ 'command': 'colo-passthrough-del', 'boxed': true,
> > +     'data': 'IPFlowSpec' }
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK