Date: Thu, 18 Jan 2018 00:31:03 +0000 From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> Cc: "Ryan Stone" <rysto32@gmail.com>, freebsd-net <freebsd-net@freebsd.org> Subject: Re: Allowing a local subnet route to change to a different ifnet Message-ID: <B68EEA08-E6C3-4965-A913-C01308BF3B57@lists.zabbadoz.net> In-Reply-To: <201801180009.w0I09vD7065398@pdx.rh.CN85.dnsmgr.net> References: <201801180009.w0I09vD7065398@pdx.rh.CN85.dnsmgr.net>
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On 18 Jan 2018, at 0:09, Rodney W. Grimes wrote: >> I have a customer that has configured two different IPs on the same >> subnet on two different interfaces. The behaviour that they want is >> that if the link on one of the two interfaces goes down, the route to >> that subnet will migrate to the other IP on the other interface as a >> quasi-failover behaviour. Under FreeBSD 7, we had a daemon that >> accomplished this by detecting the link loss and then using "route >> change" to move the route to the up interface. If the subnet in >> question was 192.168.1.0/24, for example, we could run "route change >> 192.1.68.1.0/24 -ifp em1" to migrate the route. > > "route change 192.1.68.1.0/24 -ifp em1" does not appear to be > valid syntax to me, -ifp is not a route option? > Did you mean -interface? The proper syntax should be route change -ifp <if_name> <network> but that’s not the issue (the other syntax works or used to work but not according to specification). >> Running on -head I run into two issues. The first comes out of >> r264986, which changes the behaviour of RTM_CHANGE. The code path >> changed significantly, but the part that impacts me is that now any >> RTM_CHANGE command with the gateway set NULL gets EINVAL immediately >> where previously it was allowed. I've hacked around this problem >> locally for testing purposes but I really don't understand the code >> well enough at this point to see what a real fix would look like. Running route -n monitor & while doing the change I get very weird results (without your patch). [ignore the patch for the moment] >> My first, and most important question, is whether a patch that would >> allow a subnet route to be migrated to a different interface be >> something that would be acceptable in FreeBSD? Yes. >> If so, I need guidance >> on what a proper fix for both issues would look like so that I can >> implement fixes that I can upstream. > > From a fundemental standpoint this should work, > that it is now broken is a regression that needs fixed. +1 /bz
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