Re: [ovs-dev] datapath flow will match packet's tll when we use dec_ttl in action

[Ben Pfaff]

On Wed, May 29, 2019 at 08:26:12PM +0800, ychen wrote:
> hi,
>when I send IP packets with ttl in IP header is random in range(1-255), 
> and with all other IP header fields stay not changed
> but generated 255 datapath flows each with different ttl value.
> of course, i use the action dec_ttl,  here is code:
> case OFPACT_DEC_TTL:
> wc->masks.nw_ttl = 0xff; 
> 
> 
>my question is: can we optimize the dec_ttl action? only differentiate 
> TTL>1 and TTL <=1?
>as we all know, when TTL=0, we should send packet to the controller, and 
> let it make decision whether we should send icmp error packet out.
>when TTL is larger than 1, I think they are no difference, am i right?

This optimization is not too valuable, because in practice IP packets
don't have random TTLs.
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[ovs-dev] datapath flow will match packet's tll when we use dec_ttl in action

[ychen]

hi,
   when I send IP packets with ttl in IP header is random in range(1-255), and 
with all other IP header fields stay not changed
but generated 255 datapath flows each with different ttl value.
of course, i use the action dec_ttl,  here is code:
case OFPACT_DEC_TTL:
wc->masks.nw_ttl = 0xff; 


   my question is: can we optimize the dec_ttl action? only differentiate TTL>1 
and TTL <=1?
   as we all know, when TTL=0, we should send packet to the controller, and let 
it make decision whether we should send icmp error packet out.
   when TTL is larger than 1, I think they are no difference, am i right?




   
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