[pox-dev] On 'str' object has no attribute 'buffer_id'

[Murphy McCauley]

In the spec, ofp_flow_mod doesn't have a data parameter.  POX has a special case to support a common pattern, and your code isn't it.

You should just do a flow_mod followed by a packet_out (possibly to the OFPP_TABLE special port).

-- Murphy

On Jul 26, 2013, at 9:00 AM, Keqiang He wrote:

> I refined the last message so that it is more clear:
> 
> Hello --
> 
> I want to install and modify flow entries from the controller. First, I proactively install new rules into the flow table in this way:
> 
> #flow generate-- simulated flows
> for i in "a set of ip addresses":
>     u = udp()
>     u.srcport = 1
>     u.dstport = 2
>     p = ipv4()
>     p.set_payload(u)
>     p.srcip =IPAddr(i)#i is increased ip address such as 192.168.0.1, 192.168.0.2, 192.168.0.3, ... 192.168.1.255 ...
>     p.dstip = IPAddr("192.168.56.100")
>    e =ethernet (...)
>    e.set_payload(p)
> #get a match from packet and tries to install a new rule...
>    msg = of.ofp_flow_mod()
>    msg.match = of.ofp_match.from_packet(packet)
>    msg.idle_timeout = 0
>    msg.hard_timeout = 0
>    msg.actions.append(of.ofp_action_output(port = 1))
>    self.connection.send(msg)
> Till now, the results is what I expected-- a set of new rules are installed in the flow table;
> 
> Next, I want to modify the installed (newly installed rules).  At the same time, I want to send out a packet which matches a particular rules so that I know that modified rule takes effect.
> 
> The code is like this--
> #repeat the "flow generate-- simulated flows" procedure
> ...
> #
> #get a match from packet and tries to modify that rule...
> 
>    msg = of.ofp_flow_mod()
>    msg.command = of.OFPFC_MODIFY (make sure that this command is for modification)
>    msg.match = of.ofp_match.from_packet(packet)
>    msg.idle_timeout = 0
>    msg.hard_timeout = 0
>    msg.data = e.pack()
>    msg.actions.append(of.ofp_action_output(port = 2)) # the output port is modified here...
>    self.connection.send(msg)
> Now, I get the error: 
> ********error message*****************
> File "/home/sdn/pox/pox/openflow/
> of_01.py", line 687, in send
>     data = data.pack()
>   File "/home/sdn/pox/pox/openflow/libopenflow_01.py", line 2191, in pack
>     self.buffer_id = self.data.buffer_id
> AttributeError: 'str' object has no attribute 'buffer_id'
> *********error message end**********
> 
> I tested that If I change msg = of.ofp_flow_mod() to msg = of.ofp_packet_out(), it is fine. But I do not just want to send packet out. What I want to do is, first modify a rule and then send out a packet matching that rule.
> 
> 
> Can anyone help on the error? Thanks:)
> 
> -------------end of the message---------------------
> 
> 
> 
> On Fri, Jul 26, 2013 at 11:55 AM, Keqiang He <hekeqiang at gmail.com> wrote:
> Hello --
> 
> I want to install and modify flow entries from the controller. First, I proactively install new rules into the flow table in this way:
> 
> #flow generate-- simulated flows
> for i in "a set of ip addresses":
>     u = udp()
>     u.srcport = 1
>     u.dstport = 2
>     p = ipv4()
>     p.set_payload(u)
>     p.srcip =IPAddr(i)#i is increased ip address such as 192.168.0.1, 192.168.0.2, 192.168.0.3, ... 192.168.1.255 ...
>     p.dstip = IPAddr("192.168.56.100")
>    e =ethernet (...)
>    e.set_payload(p)
> #get a match from packet and tries to install a new rule...
>    msg = of.ofp_flow_mod()
>    msg.match = of.ofp_match.from_packet(packet, event.port)
>    msg.idle_timeout = 10
>    msg.hard_timeout = 30
>    msg.actions.append(of.ofp_action_output(port = port))
>    self.connection.send(msg)
> Till now, the results is what I expected-- a set of new rules are installed in the flow table;
> 
> Next, I want to modify the installed (newly installed rules).  At the same time, I want to send out a packet which matches a particular rules so that I know that modified rule takes effect.
> 
> The code is like this--
> #repeat the "flow generate-- simulated flows" procedure
> ...
> #
> #get a match from packet and tries to modify that rule...
> 
>    msg = of.ofp_flow_mod()
>    msg.command = of.OFPFC_MODIFY (make sure that this command is for modification)
>    msg.match = of.ofp_match.from_packet(packet, event.port)
>    msg.idle_timeout = 10
>    msg.hard_timeout = 30
>    msg.data = e.pack()
>    msg.actions.append(of.ofp_action_output(port = port))
>    self.connection.send(msg)
> Now, I get the error: 
> ********error message*****************
> File "/home/sdn/pox/pox/openflow/of_01.py", line 687, in send
>     data = data.pack()
>   File "/home/sdn/pox/pox/openflow/libopenflow_01.py", line 2191, in pack
>     self.buffer_id = self.data.buffer_id
> *********error message end**********
> 
> I tested that If I change msg = of.ofp_flow_mod() to msg = of.ofp_packet_out(), it is fine. But I do not just want to send packet out. What I want to do is, first modify a rule and then send out a packet matching that rule.
> 
> 
> Can anyone help on the error? Thanks:)
> AttributeError: 'str' object has no attribute 'buffer_id'
> 
> 

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