netdev - Re: [PATCH net 2/2] net: ipv6: fix dst ref loops in rpl, seg6 and ioam6 lwtunnels

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Message-ID: <20250129121408.0fe5d481@kernel.org>
Date: Wed, 29 Jan 2025 12:14:08 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Justin Iurman <justin.iurman@...ege.be>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org,
 dsahern@...nel.org
Subject: Re: [PATCH net 2/2] net: ipv6: fix dst ref loops in rpl, seg6 and
 ioam6 lwtunnels

On Wed, 29 Jan 2025 17:50:14 +0100 Justin Iurman wrote:
> > +		if (dst->lwtstate != cache_dst->lwtstate) {
> > +			local_bh_disable();
> > +			dst_cache_set_ip6(&ilwt->cache, cache_dst, &fl6.saddr);
> > +			local_bh_enable();
> > +		}  
> 
> I agree the above patch fixes what kmemleak reported. However, I think 
> it'd bring the double-reallocation issue back when the packet 
> destination did not change (i.e., cache will always be empty). I'll try 
> to come up with a solution...

True, dunno enough about use cases so I may be missing the point.
But the naive solution would be to remember that the tunnel "doesn't
re-route" and use dst directly, instead of cache_dst?