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

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Date:   Mon, 10 Sep 2018 13:07:11 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Xin Long <lucien.xin@...il.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 9/10/18 11:55 AM, Xin Long wrote:
> 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?
> 

sure