>-----Original Message----- >From: Florian Fainelli [mailto:f.faine...@gmail.com] >Sent: Sunday, February 05, 2017 10:55 PM >To: Yotam Gigi <yot...@mellanox.com>; step...@networkplumber.org; >netdev@vger.kernel.org; Jiri Pirko <j...@mellanox.com>; Elad Raz ><el...@mellanox.com> >Subject: Re: [PATCH iproute2/net-next 1/3] tc: Add support for the sample tc >action > >Le 02/05/17 à 12:22, Yotam Gigi a écrit : >>> -----Original Message----- >>> From: Florian Fainelli [mailto:f.faine...@gmail.com] >>> Sent: Sunday, February 05, 2017 8:37 PM >>> To: Yotam Gigi <yot...@mellanox.com>; step...@networkplumber.org; >>> netdev@vger.kernel.org; Jiri Pirko <j...@mellanox.com>; Elad Raz >>> <el...@mellanox.com> >>> Subject: Re: [PATCH iproute2/net-next 1/3] tc: Add support for the sample tc >action >>> >>> On 02/04/2017 11:58 PM, Yotam Gigi wrote: >>>> The sample tc action allows sampling packets matching a classifier. It >>>> peeks randomly packets, and samples them using the psample netlink >>>> channel. The user can specify the psample group, which the packet will be >>>> sampled to, the sampling rate and the packet truncation (to save >>>> kernel-user traffic). >>>> >>>> The sampled packets contain informative metadata, for example, the input >>>> interface and the original packet length. >>>> >>>> The action syntax: >>>> tc filter add [...] \ >>>> action sample rate <RATE> group <GROUP> [trunc <SIZE>] >>>> [...] >>>> >>>> Where: >>>> RATE := The sampling rate which is the ratio of packets observed at the >>>> data source to the samples generated >>>> GROUP := the psample module sampling group >>>> SIZE := optional truncation size >>>> >>>> An example for a common usecase of the sample tc action: to sample ingress >>>> traffic from interface eth1, one may use the commands: >>>> >>>> tc qdisc add dev eth1 handle ffff: ingress >>>> >>>> tc filter add dev eth1 parent ffff: \ >>>> matchall action sample rate 12 group 4 >>>> >>>> Where the first command adds an ingress qdisc and the second starts >>>> sampling randomly with an average of one sampled packet per 12 packets >>>> on dev eth1 to psample group 4. >>> >>> The group argument seems to be mandatory from looking at the code, but >>> what if just wanted to have a port mirroring between, say sw0p1 and >>> sw0p2 with the sample rate specified instead (without using the psample >>> netlink channel at all)? Could we make this group an optional argument >>> instead? >> >> The kernel action currently don't support it, and I am not sure it should. >> >> If I understand you correctly, you want to make the sample action identical >> to mirred-mirror, only with random behavior. This can be done using the >> matchall and mirred action, plus the 'random' gact keyword. > >It sounds like we can indeed, with random determ and using the VAL >argument we should be able to configure the capture divider; thanks!
You're welcome. It took me some time to find that keyword too :) > >> >> The sample action attaches some metadata in addition to the original packet >> data, and that cannot be achieved by mirroring the packets, thus making it >> unusable for our usecase. In the former version we attached the metadata >> using the IFE protocol, but we decided to use a dedicated netlink channel >> instead. > >Yeah I see that now, thanks for the explanation! >-- >Florian
