netdev - Re: [PATCH net] ipv6: use rt6_info members when dst is set in rt6_fill

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Message-ID: <CADvbK_fJCA9PUqzsuFjVYgMtfM1tvtq32=OU90PPykq8CPP=PA@mail.gmail.com>
Date:   Tue, 11 Sep 2018 01:55:24 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     David Ahern <dsa@...ulusnetworks.com>
Cc:     network dev <netdev@...r.kernel.org>, davem <davem@...emloft.net>,
        Roopa Prabhu <roopa@...ulusnetworks.com>
Subject: Re: [PATCH net] ipv6: use rt6_info members when dst is set in rt6_fill_node

On Tue, Sep 11, 2018 at 12:13 AM David Ahern <dsa@...ulusnetworks.com> wrote:
>
> On 9/9/18 12:29 AM, Xin Long wrote:
> >>> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> >>> index 18e00ce..e554922 100644
> >>> --- a/net/ipv6/route.c
> >>> +++ b/net/ipv6/route.c
> >>> @@ -4670,20 +4670,33 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
> >>>                        int iif, int type, u32 portid, u32 seq,
> >>>                        unsigned int flags)
> >>>  {
> >>> -     struct rtmsg *rtm;
> >>> +     struct rt6key *fib6_prefsrc, *fib6_dst, *fib6_src;
> >>> +     struct rt6_info *rt6 = (struct rt6_info *)dst;
> >>> +     u32 *pmetrics, table, fib6_flags;
> >>>       struct nlmsghdr *nlh;
> >>> +     struct rtmsg *rtm;
> >>>       long expires = 0;
> >>> -     u32 *pmetrics;
> >>> -     u32 table;
> >>>
> >>>       nlh = nlmsg_put(skb, portid, seq, type, sizeof(*rtm), flags);
> >>>       if (!nlh)
> >>>               return -EMSGSIZE;
> >>>
> >>> +     if (rt6) {
> >>> +             fib6_dst = &rt6->rt6i_dst;
> >>> +             fib6_src = &rt6->rt6i_src;
> >>> +             fib6_flags = rt6->rt6i_flags;
> >>> +             fib6_prefsrc = &rt6->rt6i_prefsrc;
> >>> +     } else {
> >>> +             fib6_dst = &rt->fib6_dst;
> >>> +             fib6_src = &rt->fib6_src;
> >>> +             fib6_flags = rt->fib6_flags;
> >>> +             fib6_prefsrc = &rt->fib6_prefsrc;
> >>> +     }
> >>
> >> Unless I am missing something at the moment, an rt6_info can only have
> >> the same dst, src and prefsrc as the fib6_info on which it is based.
> >> Thus, only the flags is needed above. That simplifies this patch a lot.
> > If dst, src and prefsrc in rt6_info are always the same as these in fib6_info,
> > why do we need them in rt6_info? we could just get it by 'from'.
> >
>
> I just sent a patch removing rt6i_prefsrc. It is set with only 1 reader
> that can be converted.
>
> rt6i_src is checked against the fib6_info to invalidate a dst if the src
> has changed, so a valid rt will always have the same rt6i_src as the
> rt->from.
>
> rt6i_dst is set to the dest address / 128 in cases, so it should be used
> for rt6_info cases above.
So that means, I will use rt6i_dst and rt6i_flags when dst is set?
how about I use rt6i_src there as well? just to make it look clear.
and plus the gw/nh dump fix in rt6_fill_node():
-        if (rt->fib6_nsiblings) {
+        if (rt6) {
+                if (fib6_flags & RTF_GATEWAY)
+                        if (nla_put_in6_addr(skb, RTA_GATEWAY,
+                                             &rt6->rt6i_gateway) < 0)
+                                goto nla_put_failure;
+
+                if (dst->dev && nla_put_u32(skb, RTA_OIF, dst->dev->ifindex))
+                        goto nla_put_failure;
+        } else if (rt->fib6_nsiblings) {
                 struct fib6_info *sibling, *next_sibling;
                 struct nlattr *mp;

looks good to you?