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Message-ID: <54EEDF9C.20302@6wind.com> Date: Thu, 26 Feb 2015 09:55:56 +0100 From: Nicolas Dichtel <nicolas.dichtel@...nd.com> To: "Eric W. Biederman" <ebiederm@...ssion.com> CC: Eugene Yakubovich <eugene.yakubovich@...eos.com>, netdev@...r.kernel.org Subject: Re: What are the intended semantics of IFLA_LINK_NETNSID? Le 25/02/2015 20:03, Eric W. Biederman a écrit : > > Reading through the code of rtnl_newlink I am perplexed with what your > intended semantics of IFLA_LINK_NETNSID are supposed to be. > > My expectation was something with the same semantics IFLA_NET_NS_PID and > IFLA_NET_NS_FD just a different data representation and something that > could be used in more netlink messages, so you could report the network > namespace where the other end of a tunnel or the the network namespace > of an underlying device is. > > Being very slow I would expect that ILFA_LINK_NETNSID would replace > dest_net or possibly net in rtnl_newlink but it does not replace either > of those completely. Which causes me to think that the implementation > of IFLA_LINK_NETNSID in rtnl_newlink is broken. > > I suspect the correct fix for rtnl_newlink is to just use > IFLA_LINK_NETNSID in rtnl_link_get_net and have it be an alternative way > of setting dest_net. But you may intend some different semantics that > I don't understand. ILFA_LINK_NETNSID is used to point to the i/o netns of the interface, ie the opposite netns of dest_net. The interface is first created in link_net and moved at the end in dest_net. IP tunnels interfaces (ipip, sit, ip6_tunnels, gre[v6]) does not use src_net, thus when you create an ipip interface by specifying an attribute IFLA_NET_NS_PID it will result to an interface which is not across two netns but only in the netns pointed by IFLA_NET_NS_PID. If you use IFLA_LINK_NETNSID, it allows you to create this kind of x-netns interfaces. In fact, the goal of this attribute is to replace the two following command by only one: ip link add foo ... ip link set foo netns bar => ip link add foo link-netnsid barID Regards, Nicolas -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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