netdev - Re: [PATCH net-next] rtnetlink: Honour NLM_F_ECHO flag in rtnl

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Date:   Wed, 21 Sep 2022 18:31:19 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Nicolas Dichtel <nicolas.dichtel@...nd.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Ido Schimmel <idosch@...dia.com>,
        Petr Machata <petrm@...dia.com>,
        Florent Fourcot <florent.fourcot@...irst.fr>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Guillaume Nault <gnault@...hat.com>
Subject: Re: [PATCH net-next] rtnetlink: Honour NLM_F_ECHO flag in rtnl_{new,
 set}link

On Wed, Sep 21, 2022 at 11:11:19AM +0200, Nicolas Dichtel wrote:
> > @@ -3336,9 +3381,9 @@ static int rtnl_newlink_create(struct sk_buff *skb, struct ifinfomsg *ifm,
> >  		return PTR_ERR(dest_net);
> >  
> >  	if (tb[IFLA_LINK_NETNSID]) {
> > -		int id = nla_get_s32(tb[IFLA_LINK_NETNSID]);
> > +		netnsid = nla_get_s32(tb[IFLA_LINK_NETNSID]);
> >  
> > -		link_net = get_net_ns_by_id(dest_net, id);
> > +		link_net = get_net_ns_by_id(dest_net, netnsid);
> >  		if (!link_net) {
> >  			NL_SET_ERR_MSG(extack, "Unknown network namespace id");
> >  			err =  -EINVAL;
> > @@ -3382,6 +3427,17 @@ static int rtnl_newlink_create(struct sk_buff *skb, struct ifinfomsg *ifm,
> >  		if (err)
> >  			goto out_unregister;
> >  	}
> > +
> > +	if (nlmsg_flags & NLM_F_ECHO) {
> > +		u32 ext_filter_mask = 0;
> > +
> > +		if (tb[IFLA_EXT_MASK])
> > +			ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
> > +
> > +		rtnl_echo_link_info(dev, NETLINK_CB(skb).portid, nlmsg_seq,
> > +				    ext_filter_mask, netnsid);
> => netnsid, ie IFLA_LINK_NETNSID has nothing to do with IFLA_TARGET_NETNSID.
> Link netns is used for x-netns interface like vlan for example. The vlan iface
> could be in a netns while its lower iface could be in another netns.
> 
> The target netns is used when a netlink message is sent in a netns but should
> act in another netns.

Oh, thanks for the explanation. Then we can remove the netnsid parameter
from rtnl_echo_link_info().

Thanks
Hangbin