netdev - Re: [PATCH net 1/2] ipv6: add ipv6_dev

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Date:   Sun, 9 Aug 2020 19:04:21 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Hideaki Yoshifuji <hideaki.yoshifuji@...aclelinux.com>
Cc:     David Ahern <dsahern@...il.com>,
        network dev <netdev@...r.kernel.org>,
        davem <davem@...emloft.net>, Ying Xue <ying.xue@...driver.com>,
        tipc-discussion@...ts.sourceforge.net,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, jmaloy@...hat.com
Subject: Re: [PATCH net 1/2] ipv6: add ipv6_dev_find()

On Fri, Aug 7, 2020 at 5:26 PM Hideaki Yoshifuji
<hideaki.yoshifuji@...aclelinux.com> wrote:
>
> Hi,
>
> 2020年8月6日(木) 23:03 David Ahern <dsahern@...il.com>:
> >
> > On 8/6/20 2:55 AM, Xin Long wrote:
> > > On Thu, Aug 6, 2020 at 10:50 AM Hideaki Yoshifuji
> > > <hideaki.yoshifuji@...aclelinux.com> wrote:
> > >>
> > >> Hi,
> > >>
> > >> 2020年8月4日(火) 0:35 Xin Long <lucien.xin@...il.com>:
> > >>>
> > >>> This is to add an ip_dev_find like function for ipv6, used to find
> > >>> the dev by saddr.
> > >>>
> > >>> It will be used by TIPC protocol. So also export it.
> > >>>
> > >>> Signed-off-by: Xin Long <lucien.xin@...il.com>
> > >>> ---
> > >>>  include/net/addrconf.h |  2 ++
> > >>>  net/ipv6/addrconf.c    | 39 +++++++++++++++++++++++++++++++++++++++
> > >>>  2 files changed, 41 insertions(+)
> > >>>
> > >>> diff --git a/include/net/addrconf.h b/include/net/addrconf.h
> > >>> index 8418b7d..ba3f6c15 100644
> > >>> --- a/include/net/addrconf.h
> > >>> +++ b/include/net/addrconf.h
> > >>> @@ -97,6 +97,8 @@ bool ipv6_chk_custom_prefix(const struct in6_addr *addr,
> > >>>
> > >>>  int ipv6_chk_prefix(const struct in6_addr *addr, struct net_device *dev);
> > >>>
> > >>> +struct net_device *ipv6_dev_find(struct net *net, const struct in6_addr *addr);
> > >>> +
> > >>
> > >> How do we handle link-local addresses?
> > > This is what "if (!result)" branch meant to do:
> > >
> > > +       if (!result) {
> > > +               struct rt6_info *rt;
> > > +
> > > +               rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);
> > > +               if (rt) {
> > > +                       dev = rt->dst.dev;
> > > +                       ip6_rt_put(rt);
> > > +               }
> > > +       } else {
> > > +               dev = result->idev->dev;
> > > +       }
> > >
> >
> > the stated purpose of this function is to find the netdevice to which an
> > address is attached. A route lookup should not be needed. Walking the
> > address hash list finds the address and hence the netdev or it does not.
> >
> >
>
> User supplied scope id which should be set for link-local addresses
> in TIPC_NLA_UDP_LOCAL attribute must be honored when we
> check the address.
Hi, Hideaki san,

Sorry for not understanding your comment earlier.

The bad thing is tipc in iproute2 doesn't seem able to set scope_id.
I saw many places in kernel doing this check:

                         if (__ipv6_addr_needs_scope_id(atype) &&
                             !ip6->sin6_scope_id) { return -EINVAL; }

Can I ask why scope id is needed for link-local addresses?
and is that for link-local addresses only?

>
> ipv6_chk_addr() can check if the address and supplied ifindex is a valid
> local address.  Or introduce an extra ifindex argument to ipv6_dev_find().
Yeah, but if scope id means ifindex for  link-local addresses, ipv6_dev_find()
would be more like a function to validate the address with right scope id.

Thanks for your reviewing.