netdev - Re: [PATCH net] Revert "tcp/dccp: get rid of inet_twsk

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Date:   Fri, 13 May 2022 12:40:41 +0300
From:   Leonard Crestez <cdleonard@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net] Revert "tcp/dccp: get rid of inet_twsk_purge()"

On 13.05.2022 00:14, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> This reverts commits:
> 
> 0dad4087a86a2cbe177404dc73f18ada26a2c390 ("tcp/dccp: get rid of inet_twsk_purge()")
> d507204d3c5cc57d9a8bdf0a477615bb59ea1611 ("tcp/dccp: add tw->tw_bslot")
> 
> As Leonard pointed out, a newly allocated netns can happen
> to reuse a freed 'struct net'.
> 
> While TCP TW timers were covered by my patches, other things were not:
> 
> 1) Lookups in rx path (INET_MATCH() and INET6_MATCH()), as they look
>    at 4-tuple plus the 'struct net' pointer.
> 
> 2) /proc/net/tcp[6] and inet_diag, same reason.
> 
> 3) hashinfo->bhash[], same reason.
> 
> Fixing all this seems risky, lets instead revert.
> 
> In the future, we might have a per netns tcp hash table, or
> a per netns list of timewait sockets...
> 
> Fixes: 0dad4087a86a ("tcp/dccp: get rid of inet_twsk_purge()")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Leonard Crestez <cdleonard@...il.com>

Tested-by: Leonard Crestez <cdleonard@...il.com>