[ovs-discuss] Flow Monitoring

Vasu Dasari vdasari at gmail.com
Fri May 24 02:46:40 UTC 2019


Thanks for digging into this. My comments inline. I am sorry that I had to
differ from your analysis.

*Vasu Dasari*


On Thu, May 23, 2019 at 5:54 PM Ben Pfaff <blp at ovn.org> wrote:

> On Thu, May 23, 2019 at 04:37:41PM -0400, Vasu Dasari wrote:
> > There are two "flags" fields in tcpdump output I shared earlier.
> > 1. First one is 0 which is part of OFPT_MULTIPART_REQUEST, saying there
> are
> > no more parts. This is first two bytes in row 0040
> > 2. And second one is "00 01" and it is indicating to receive "add"
> > notifications. And these are 2nd two bytes in row 0050.
> >
> > Can you tell which bytes do you think are representing "flags" field in
> > above bytes output?
> >
> > You can open the pcap file in Wireshark to see my analysis.
>
> Stripping off the TCP and other headers, we have the following:
>
> 00000000  05 12 00 28 00 00 00 00-00 10 00 00 00 00 00 00
> |...(............|
> 00000010  05 f5 e1 00 00 00 00 00-ff ff ff ff 00 01 00 00
> |................|
> 00000020  00 01 00 04 00 00 00 00-                        |........
> |
>
> "05 f5 e1 00" is the id, the following 00 00 is the flags.
>

05 f5 e1 00 => Is Monitor Id which is decimal 100000000, set by controller.
And field after that is "00 00 00 00" which is Out Port.
ff ff ff ff => Out Group
00 01 => Monitor Flags, "Initial" bit is set.
00 => Table Id - 0
00 => Add Operation

So from above parsing I see that flags is set as "00 01".



>
> > Also, is there a specification for nicera extensions? Can you please
> point
> > it to me?
>
> Beyond the 100+ relevant lines of comments in nicira-ext.h?  No.
>
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