netdev - Re: net: vrf: Handle ipv6 multicast and link-local addresses

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Message-ID: <1d0eb1d8-708f-2238-37c9-b75004804065@cumulusnetworks.com>
Date:	Wed, 3 Aug 2016 14:11:49 -0600
From:	David Ahern <dsa@...ulusnetworks.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: net: vrf: Handle ipv6 multicast and link-local addresses

On 8/3/16 1:57 PM, Geert Uytterhoeven wrote:
>> +static void vrf_ip6_input_dst(struct sk_buff *skb, struct net_device *vrf_dev,
>> > +                             int ifindex)
>> > +{
>> > +       const struct ipv6hdr *iph = ipv6_hdr(skb);
>> > +       struct flowi6 fl6 = {
>> > +               .daddr          = iph->daddr,
>> > +               .saddr          = iph->saddr,
>> > +               .flowlabel      = ip6_flowinfo(iph),
> The above assignment causes the following compiler warning with
> m68k-linux-gnu-gcc-4.1:
> 
>     drivers/net/vrf.c: In function ‘vrf_ip6_input_dst’:
>     drivers/net/vrf.c:870: warning: initialized field with
> side-effects overwritten
>     drivers/net/vrf.c:870: warning: (near initialization for ‘fl6’)
> 
> Unfortunately I have no idea what it means, nor do I see what's wrong
> with the code.

no idea. Fields are initialized once and left and right data types are the same.

Can you remove one line at a time? Line 870 is ".flowi6_proto   = iph->nexthdr," but all of the flowi6 macros are unique references to unique fields in flowi_common. The flowlabel line you point out is a unique field as well.

Can you run pahole on file that did compile? e.g.,

pahole -C 'flowi6' net/ipv6/route.o

and get the common struct too:

pahole -C 'flowi_common' net/ipv6/route.o

> 
>> > +               .flowi6_mark    = skb->mark,
>> > +               .flowi6_proto   = iph->nexthdr,
>> > +               .flowi6_iif     = ifindex,
>> > +       };