On 16-11-10 11:58 AM, Yotam Gigi wrote: > > >> -----Original Message----- >> From: John Fastabend [mailto:john.fastab...@gmail.com] >> Sent: Thursday, November 10, 2016 9:38 PM >> To: Jiri Pirko <j...@resnulli.us>; netdev@vger.kernel.org >> Cc: da...@davemloft.net; Yotam Gigi <yot...@mellanox.com>; Ido Schimmel >> <ido...@mellanox.com>; Elad Raz <el...@mellanox.com>; Nogah Frankel >> <nog...@mellanox.com>; Or Gerlitz <ogerl...@mellanox.com>; >> j...@mojatatu.com; geert+rene...@glider.be; step...@networkplumber.org; >> xiyou.wangc...@gmail.com; li...@roeck-us.net; ro...@cumulusnetworks.com >> Subject: Re: [patch net-next 5/8] Introduce sample tc action >> >> On 16-11-10 11:35 AM, John Fastabend wrote: >>> On 16-11-10 03:23 AM, Jiri Pirko wrote: >>>> From: Yotam Gigi <yot...@mellanox.com> >>>> >>>> This action allow the user to sample traffic matched by tc classifier. >>>> The sampling consists of choosing packets randomly, truncating them, >>>> adding some informative metadata regarding the interface and the original >>>> packet size and mark them with specific mark, to allow further tc rules to >>>> match and process. The marked sample packets are then injected into the >>>> device ingress qdisc using netif_receive_skb. >>>> >>>> The packets metadata is packed using the ife encapsulation protocol, and >>>> the outer packet's ethernet dest, source and eth_type, along with the >>>> rate, mark and the optional truncation size can be configured from >>>> userspace. >>>> >>>> Example: >>>> To sample ingress traffic from interface eth1, and redirect the sampled >>>> the sampled packets to interface dummy0, 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 mark 17 >>>> >>>> tc filter add parent ffff: dev eth1 protocol all \ >>>> u32 match mark 17 0xff \ >>>> action mirred egress redirect dev dummy0 >>>> >>>> Where the first command adds an ingress qdisc and the second starts >>>> sampling every 12'th packet on dev eth1 and marks the sampled packets with >>>> 17. The third command catches the sampled packets, which are marked with >>>> 17, and redirects them to dev dummy0. >>> >>> The sampling algorithm was not randomized based on the above commit >>> log? It really needs to be for all the reasons Roopa mentioned earlier. >>> Did I miss some email on why it didn't get implemented? >>> >>> Also there was an indication the already is actually implemented >>> correctly so don't we need the hw/sw to behave the same. The whole >>> argument about sw/hw parity, etc. >> >> sorry bit of a typo there corrected 2nd paragraph here... >> >> Also there was an indication the hardware is already implemented \ >> correctly so don't we need the hw/sw to behave the same. The argument >> about sw/hw parity, etc. > > Our hardware currently does not support sampling with random behavior, so > we did implement it in software too. > > But, the API is extensible and it is possible to add a random keyword to > the tc action to allow random sampling. In that case, the keyword will be > implemented in sw only and our driver will fail offloading it. >
For many use cases this will be limiting but OK maybe this is good enough for something and we can add a flag/attribute to support random sampling. Works for me.
