From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brandon Philips Subject: fib_frontend: Add network specific broadcasts, when it takes a sense Date: Fri, 9 Dec 2016 15:41:52 -0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 To: netdev@vger.kernel.org, Tom Denham , Aaron Levy , Brad Ison Return-path: Received: from mail-oi0-f48.google.com ([209.85.218.48]:35467 "EHLO mail-oi0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750728AbcLIXlx (ORCPT ); Fri, 9 Dec 2016 18:41:53 -0500 Received: by mail-oi0-f48.google.com with SMTP id b126so34869132oia.2 for ; Fri, 09 Dec 2016 15:41:53 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: Hello- A number of us are working on an OSS overlay network system called flannel. It is used in a variety of Linux container systems and one of the backends is VXLAN. The issue we have: when creating the VXLAN interface and assigning it an address we see a broadcast route being added by the Kernel. For example if we have 10.4.0.0/16 a broadcast route to 10.4.0.0 is created. This route is unwanted because we assign 10.4.0.0 to one of our VXLAN interfaces. However, the Kernel interface bring-up comment reads: Add network specific broadcasts, when it takes a sense. The code is here: https://github.com/torvalds/linux/blob/master/net/ipv4/fib_frontend.c#L859-L872 Can someone explain why creation of the broadcast route is non-optional? Would a patch to make it optional be acceptable? Is it safe for us to simply delete the route? We have a patch that simply deletes the broadcast route after interface creation but don't know why the Kernel code "makes sense". You can read more information about the issue here: https://github.com/coreos/flannel/pull/569 Thank You, Brandon