[pox-dev] POX - TCP redirection flows

[chenli]

Hello everyone:


I'm using POX to redirect tcp traffic, it just modify the action output and
destination IP and MAC address.

But when I modify the code in POX to do tcp flow redirection, I got
confused about the abnormal flows like below:

The normal redirection flows:

 cookie=0x0, duration=8.668s, table=0, n_packets=26, n_bytes=2651,
idle_timeout=30,
tcp,dl_vlan=0,dl_vlan_pcp=0,dl_src=ac:f1:df:79:29:be,dl_dst=c8:be:19:49:d7:d2,nw_src=192.168.15.110,nw_dst=192.168.15.197,
nw_tos=0,tp_src=22,tp_dst=55029
actions=mod_dl_src:c8:be:19:49:d7:d1,output:46
 cookie=0x0, duration=8.652s, table=0, n_packets=33, n_bytes=3363,
idle_timeout=30,
tcp,dl_vlan=0,dl_vlan_pcp=0,dl_src=c8:be:19:49:d7:d2,dl_dst=c8:be:19:49:d7:d1,nw_src=192.168.15.197,nw_dst=192.168.15.110,
nw_tos=0,tp_src=55029,tp_dst=22
actions=mod_dl_dst:ac:f1:df:79:29:be,output:42

On the general case, the tcp traffic will follow the above two flows to do
transmission.

But the strange thing is POX also add the following two abnormal flows, so
the ssh redirection connection can't connect successfully.

The abnormal flows:

 cookie=0x0, duration=5.105s, table=0, n_packets=0, n_bytes=0,
idle_timeout=30,
tcp,dl_vlan=0,dl_vlan_pcp=0,dl_src=ac:f1:df:79:29:be,dl_dst=ac:f1:df:79:29:be,nw_src=192.168.15.197,nw_dst=192.168.15.110,
nw_tos=16,tp_src=55029,tp_dst=22
actions=mod_dl_src:c8:be:19:49:d7:d2,output:42
 cookie=0x0, duration=5.091s, table=0, n_packets=19, n_bytes=2218,
idle_timeout=30,
tcp,dl_vlan=0,dl_vlan_pcp=0,dl_src=ac:f1:df:79:29:be,dl_dst=c8:be:19:49:d7:d2,nw_src=192.168.15.110,nw_dst=192.168.15.197,
nw_tos=16,tp_src=22,tp_dst=55029
actions=mod_dl_dst:ac:f1:df:79:29:be,output:42

I got confused about the nw_tos field for abnormal flows, why it has the
value of 16 which is different from the normal redirection flows and POX
need to add it?

Thanks.
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