From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ka-Cheong Poon Subject: Re: [PATCH net-next 2/3] rds: Enable RDS IPv6 support Date: Wed, 27 Jun 2018 18:07:47 +0800 Message-ID: References: <7f4f460079d3d78a18f7d759488048798e99c4db.1529922794.git.ka-cheong.poon@oracle.com> <20180625170317.GA28578@oracle.com> <25e1afda-7497-7f08-815a-286cf775bc09@oracle.com> <20180625175006.GI14823@oracle.com> <43b790c2-8da6-9f18-ae23-ca55388e8b26@oracle.com> <20180626101657.GA20575@oracle.com> <20180626130844.GD20575@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, santosh.shilimkar@oracle.com, davem@davemloft.net, rds-devel@oss.oracle.com To: Sowmini Varadhan Return-path: Received: from aserp2120.oracle.com ([141.146.126.78]:38902 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932089AbeF0KIA (ORCPT ); Wed, 27 Jun 2018 06:08:00 -0400 In-Reply-To: <20180626130844.GD20575@oracle.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 06/26/2018 09:08 PM, Sowmini Varadhan wrote: > On (06/26/18 21:02), Ka-Cheong Poon wrote: >> >> In this case, RFC 6724 prefers link local address as source. > > the keyword is "prefers". There is a reason for that. It is the way folks expect how IPv6 addresses are being used. >> While using non-link local address (say ULA) is not forbidden, >> doing this can easily cause inter-operability issues (does the >> app really know that the non-link local source and the link >> local destination addresses are really on the same link?). I >> think it is prudent to disallow this in RDS unless there is a >> very clear and important reason to do so. > > I remember the issues that triggered 6724. The "interop" issue > is that when you send from Link-local to global, and need forwarding, > it may not work. It is not just forwarding. The simple case is that one picks a global address in a different link and then use it to send to a link local address in another link. This does not work. And the RDS connection created will be stuck forever. I don't think this is a good idea to have such stuck connections. > but I dont think an RDS application today expects to deal with > the case that "oh I got back and error when I tried to send to > address X on rds socket rs1, let me go and check what I am bound > to, and maybe create another socket, and bind it to link-local" I don't expect RDS apps will want to use link local address in the first place. In fact, most normal network apps don't. > You're not doing this for IPv4 and RDS today (you dont have to do this > for UDP, afaik) Do you know of any IPv4 RDS app which uses IPv4 link local address? In fact, IPv4 link local address is explicitly disallowed for active active bonding. > This is especially true if "X" is a hostname that got resovled using DNS Can you explain why DNS name resolution will return an IPv6 link local address? I'm surprised if it actually does. >> BTW, if it is really > needed, it can be added in future. > > shrug. You are introducing a new error return. An error needs to be returned because it is not allowed. -- K. Poon ka-cheong.poon@oracle.com