From mboxrd@z Thu Jan 1 00:00:00 1970 From: sfeldma@gmail.com Subject: [RFC PATCH net-next v2 5/5] switchdev: update documentation for offload_fwd_mark Date: Wed, 17 Jun 2015 14:53:14 -0700 Message-ID: <1434577994-22409-6-git-send-email-sfeldma@gmail.com> References: <1434577994-22409-1-git-send-email-sfeldma@gmail.com> Cc: jiri@resnulli.us, simon.horman@netronome.com, roopa@cumulusnetworks.com, ronen.arad@intel.com, john.r.fastabend@intel.com, andrew@lunn.ch, f.fainelli@gmail.com, linux@roeck-us.net, davidch@broadcom.com, stephen@networkplumber.org To: netdev@vger.kernel.org Return-path: Received: from mail-pa0-f43.google.com ([209.85.220.43]:34959 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753197AbbFQVvY (ORCPT ); Wed, 17 Jun 2015 17:51:24 -0400 Received: by pacyx8 with SMTP id yx8so45482384pac.2 for ; Wed, 17 Jun 2015 14:51:24 -0700 (PDT) In-Reply-To: <1434577994-22409-1-git-send-email-sfeldma@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Scott Feldman Signed-off-by: Scott Feldman --- Documentation/networking/switchdev.txt | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/Documentation/networking/switchdev.txt b/Documentation/networking/switchdev.txt index c5d7ade..b864e47 100644 --- a/Documentation/networking/switchdev.txt +++ b/Documentation/networking/switchdev.txt @@ -279,8 +279,18 @@ and unknown unicast packets to all ports in domain, if allowed by port's current STP state. The switch driver, knowing which ports are within which vlan L2 domain, can program the switch device for flooding. The packet should also be sent to the port netdev for processing by the bridge driver. The -bridge should not reflood the packet to the same ports the device flooded. -XXX: the mechanism to avoid duplicate flood packets is being discuseed. +bridge should not reflood the packet to the same ports the device flooded, +otherwise there will be duplicate packets on the wire. + +To avoid duplicate packets, the device/driver can mark a packet as already +forwarded using skb->offload_fwd_mark. The same mark is set on the device +ports in the domain using dev->offload_fwd_mark. If the skb->offload_fwd_mark +is non-zero and matches the forwarding egress port's dev->skb_mark, the kernel +will drop the skb right before transmit on the egress port, with the +understanding that the device already forwarded the packet on same egress port. +The driver can use switchdev_port_fwd_mark_set() to set a globally unique mark +for port's dev->offload_fwd_mark, based on the port's parent ID (switch ID) and +a group ifindex. It is possible for the switch device to not handle flooding and push the packets up to the bridge driver for flooding. This is not ideal as the number -- 1.7.10.4