[nox-dev] Getting Actions From Events in Python
Hello, I was looking at pyglue.cc and it looks like actions are never included in python events. A comment says to use Flow_stats, but flow stats contains a vector ofp_action_header's. Since actions are variable-length, won't this cut off data when the action is longer than the header? (For example, ofp_action_dl_addr). So, is there any way to get actions in events like flow stats in? If not, how could we go about implementing this? Thanks, Derek ___ nox-dev mailing list nox-dev@noxrepo.org http://noxrepo.org/mailman/listinfo/nox-dev_noxrepo.org
Re: [nox-dev] Getting Actions From Events in Python
I believe the issue is that with the to_python() for ofp_flow_stats, we have no idea if the actions actually follow the ofp_flow_stats structure since, for example, someone could have just made an ofp_flow_stats struct and tried to pythonize it. I am not sure if this ever actually happens, but whatever. It's not provably a safe thing to do. However, the Flow_stats struct actually explicitly has the actions wrapped up into a vector, so it IS possible to safely pull them out of that. It just hasn't been done. The to_python() for Flow_stats should: Step one, convert the fields from the ofp_flow_stats struct itself into dict, which is done by just calling the to_python() for ofp_flow_stats. Step two, unpack v_actions from the Flow_stats struct into a list of dicts and throw it into dict too. Except instead of step two, we have /* XXX actions */. :) You should be able to just go ahead and implement it there. -- Murphy On Fri, 2011-01-28 at 14:50 +0900, Derek Cormier wrote: Hello, I was looking at pyglue.cc and it looks like actions are never included in python events. A comment says to use Flow_stats, but flow stats contains a vector ofp_action_header's. Since actions are variable-length, won't this cut off data when the action is longer than the header? (For example, ofp_action_dl_addr). So, is there any way to get actions in events like flow stats in? If not, how could we go about implementing this? Thanks, Derek ___ nox-dev mailing list nox-dev@noxrepo.org http://noxrepo.org/mailman/listinfo/nox-dev_noxrepo.org ___ nox-dev mailing list nox-dev@noxrepo.org http://noxrepo.org/mailman/listinfo/nox-dev_noxrepo.org
Re: [nox-dev] Getting Actions From Events in Python
Ok I'll give it a try and submit a patch when I'm finished. Could you
please tell me if the following is
the right approach?
template
PyObject*
to_python(const ofp_action_header a)
{
PyObject* dict = PyDict_New();
if (!dict) {
return 0;
}
uint16_t type = ntohs(a.type);
pyglue_setdict_string(dict, type, to_python(type));
pyglue_setdict_string(dict, length, to_python(ntohs(a.len));
/* depending on the action type, cast to the appropriate
* action struct to get its fields. */
if (type == OFPAT_OUTPUT) {
const ofp_action_output ao =
reinterpret_castofp_action_output(a);
uint16_t port = ntohs(ao.port);
pyglue_setdict_string(dict, port, to_python(port));
/* max_len only has meaning when the destination port is the
controller */
if (port == OFPP_CONTROLLER) {
pyglue_setdict_string(dict, max_len,
to_python(ntohs(ao.max_len)));
}
}
else if (type == OFPAT_STRIP_VLAN) {
/* nothing to set, no struct beyond the header */
}
else if (type == OFPAT_SET_VLAN_VID) {
const ofp_action_vlan_vid av =
reinterpret_castofp_action_output(a);
Is this the proper use of reinterpret cast? I've never had to use it
before...
-Derek
On 01/28/2011 03:20 PM, James Murphy McCauley wrote:
I believe the issue is that with the to_python() for ofp_flow_stats, we
have no idea if the actions actually follow the ofp_flow_stats structure
since, for example, someone could have just made an ofp_flow_stats
struct and tried to pythonize it. I am not sure if this ever actually
happens, but whatever. It's not provably a safe thing to do. However,
the Flow_stats struct actually explicitly has the actions wrapped up
into a vector, so it IS possible to safely pull them out of that. It
just hasn't been done.
The to_python() for Flow_stats should: Step one, convert the fields from
the ofp_flow_stats struct itself into dict, which is done by just
calling the to_python() for ofp_flow_stats. Step two, unpack v_actions
from the Flow_stats struct into a list of dicts and throw it into dict
too. Except instead of step two, we have /* XXX actions */. :) You
should be able to just go ahead and implement it there.
-- Murphy
On Fri, 2011-01-28 at 14:50 +0900, Derek Cormier wrote:
Hello,
I was looking at pyglue.cc and it looks like actions are never included
in python events.
A comment says to use Flow_stats, but flow stats contains a vector
ofp_action_header's. Since actions are variable-length, won't this cut
off data when the action is longer than the header? (For example,
ofp_action_dl_addr).
So, is there any way to get actions in events like flow stats in? If
not, how could we go about implementing this?
Thanks,
Derek
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Re: [nox-dev] Getting Actions From Events in Python
Without minding the typos, that is...
On 01/28/2011 04:46 PM, Derek Cormier wrote:
Ok I'll give it a try and submit a patch when I'm finished. Could you
please tell me if the following is
the right approach?
template
PyObject*
to_python(const ofp_action_header a)
{
PyObject* dict = PyDict_New();
if (!dict) {
return 0;
}
uint16_t type = ntohs(a.type);
pyglue_setdict_string(dict, type, to_python(type));
pyglue_setdict_string(dict, length, to_python(ntohs(a.len));
/* depending on the action type, cast to the appropriate
* action struct to get its fields. */
if (type == OFPAT_OUTPUT) {
const ofp_action_output ao =
reinterpret_castofp_action_output(a);
uint16_t port = ntohs(ao.port);
pyglue_setdict_string(dict, port, to_python(port));
/* max_len only has meaning when the destination port is the
controller */
if (port == OFPP_CONTROLLER) {
pyglue_setdict_string(dict, max_len,
to_python(ntohs(ao.max_len)));
}
}
else if (type == OFPAT_STRIP_VLAN) {
/* nothing to set, no struct beyond the header */
}
else if (type == OFPAT_SET_VLAN_VID) {
const ofp_action_vlan_vid av =
reinterpret_castofp_action_output(a);
Is this the proper use of reinterpret cast? I've never had to use it
before...
-Derek
On 01/28/2011 03:20 PM, James Murphy McCauley wrote:
I believe the issue is that with the to_python() for ofp_flow_stats, we
have no idea if the actions actually follow the ofp_flow_stats structure
since, for example, someone could have just made an ofp_flow_stats
struct and tried to pythonize it. I am not sure if this ever actually
happens, but whatever. It's not provably a safe thing to do. However,
the Flow_stats struct actually explicitly has the actions wrapped up
into a vector, so it IS possible to safely pull them out of that. It
just hasn't been done.
The to_python() for Flow_stats should: Step one, convert the fields from
the ofp_flow_stats struct itself into dict, which is done by just
calling the to_python() for ofp_flow_stats. Step two, unpack v_actions
from the Flow_stats struct into a list of dicts and throw it into dict
too. Except instead of step two, we have /* XXX actions */. :) You
should be able to just go ahead and implement it there.
-- Murphy
On Fri, 2011-01-28 at 14:50 +0900, Derek Cormier wrote:
Hello,
I was looking at pyglue.cc and it looks like actions are never included
in python events.
A comment says to use Flow_stats, but flow stats contains a vector
ofp_action_header's. Since actions are variable-length, won't this cut
off data when the action is longer than the header? (For example,
ofp_action_dl_addr).
So, is there any way to get actions in events like flow stats in? If
not, how could we go about implementing this?
Thanks,
Derek
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