From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Herbert Subject: Re: [PATCH net-next] net/gtp: Add udp source port generation according to flow hash Date: Wed, 22 Feb 2017 13:47:17 -0800 Message-ID: References: <1487257141-11706-1-git-send-email-ogerlitz@mellanox.com> <576077949.135577.1487282291666.JavaMail.zimbra@tpip.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Andreas Schultz , Or Gerlitz , "David S. Miller" , Jamal Hadi Salim , pablo , laforge , netdev To: Or Gerlitz Return-path: Received: from mail-qk0-f174.google.com ([209.85.220.174]:34733 "EHLO mail-qk0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933116AbdBVVrT (ORCPT ); Wed, 22 Feb 2017 16:47:19 -0500 Received: by mail-qk0-f174.google.com with SMTP id s186so15937056qkb.1 for ; Wed, 22 Feb 2017 13:47:18 -0800 (PST) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Feb 22, 2017 at 1:29 PM, Or Gerlitz wrote: > On Thu, Feb 16, 2017 at 11:58 PM, Andreas Schultz wrote: >> Hi Or, >> ----- On Feb 16, 2017, at 3:59 PM, Or Gerlitz ogerlitz@mellanox.com wrote: >> >>> Generate the source udp header according to the flow represented by >>> the packet we are encapsulating, as done for other udp tunnels. This >>> helps on the receiver side to apply RSS spreading. >> >> This might work for GTPv0-U, However, for GTPv1-U this could interfere >> with error handling in the user space control process when the UDP port >> extension header is used in error indications. > > > in the document you posted there's this quote "The source IP and port > have no meaning and can change at any time" -- I assume it refers to > v0? can we identify in the kernel code that we're on v0 and have the > patch come into play? > >> 3GPP TS 29.281 Rel 13, section 5.2.2.1 defines the UDP port extension and >> section 7.3.1 says that the UDP source port extension can be used to >> mitigate DOS attacks. This would IMHO imply that the user space control >> process needs to know the TEID to UDP source port mapping. > >> The other question is, on what is this actually hashing. When I understand >> the code correctly, this will hash on the source/destination of the orignal >> flow. I would expect that a SGSN/SGW/eNodeB would like the keep flow >> processing on a per TEID base, so the port hashing should be base on the TEID. > > is it possible for packets belonging to the same TCP session or UDP > "pseudo session" (given pair of src/dst ip/port) to be encapsulated > using different TEID? > > hashing on the TEID imposes a harder requirement on the NIC HW vs. > just UDP based RSS. This shouldn't be taken as a HW requirement and it's unlikely we'd add explicit GTP support in flow_dissector. If we can't get entropy in the UDP source port then IPv6 flow label is a potential alternative (so that should be supported in NICs for RSS). I'll also reiterate my previous point about the need for GTP testing-- in order for us to be able to evaluate the GTP datapath for things like performance or how they withstand against DDOS we really need an easy way to isolate the datapath. Tom