From: David Miller <davem@davemloft.net>
To: kafai@fb.com
Cc: netdev@vger.kernel.org, hannes@stressinduktion.org
Subject: Re: [PATCH RFC v3 net 1/2] ipv6: Remove the net->ipv6.ip6_null_entry check
Date: Wed, 08 Oct 2014 15:08:38 -0400 (EDT) [thread overview]
Message-ID: <20141008.150838.2078642969379360127.davem@davemloft.net> (raw)
In-Reply-To: <1412640315-22472-2-git-send-email-kafai@fb.com>
From: Martin KaFai Lau <kafai@fb.com>
Date: Mon, 6 Oct 2014 17:05:14 -0700
> The above BACKTRACK have already caught the rt == net->ipv6.ip6_null_entry case
>
> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
...
> @@ -936,8 +936,7 @@ restart:
> if (rt->rt6i_nsiblings)
> rt = rt6_multipath_select(rt, fl6, oif, strict | reachable);
> BACKTRACK(net, &fl6->saddr);
> - if (rt == net->ipv6.ip6_null_entry ||
> - rt->rt6i_flags & RTF_CACHE)
> + if (rt->rt6i_flags & RTF_CACHE)
> goto out;
>
> dst_hold(&rt->dst);
I think this is sort of going in the wrong direction.
The BACKTRACK() macro hides a lot of side effects inside of it's
implementation, and worst of all it hides a change of control flow
with it's "goto out;" and "goto restart;"
I'd rather see us clean this up in some way that someone auditing this
code won't be tricked into missing the control flow side effects, than
adding more dependencies upon BACKTRACK()'s implementation.
Thanks.
next prev parent reply other threads:[~2014-10-08 19:08 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-07 0:05 [PATCH RFC v3 net 0/2] ipv6: Avoid restarting fib6_lookup() for RTF_CACHE hit Martin KaFai Lau
2014-10-07 0:05 ` [PATCH RFC v3 net 1/2] ipv6: Remove the net->ipv6.ip6_null_entry check Martin KaFai Lau
2014-10-08 19:08 ` David Miller [this message]
2014-10-07 0:05 ` [PATCH RFC v3 net 2/2] ipv6: Avoid restarting fib6_lookup() for RTF_CACHE hit case Martin KaFai Lau
2014-10-08 19:32 ` David Miller
2014-10-09 4:19 ` Martin Lau
2014-10-07 0:10 ` [PATCH RFC v3 net 0/2] ipv6: Avoid restarting fib6_lookup() for RTF_CACHE hit Hannes Frederic Sowa
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