netdev - Re: [PATCH] net-next: Fix __inet_inherit_port() to correctly increment bsockets and num

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Message-ID: <20101129131201.GB9286@ff.dom.local>
Date:	Mon, 29 Nov 2010 13:12:01 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Evgeniy Polyakov <zbr@...emap.net>
Cc:	Nagendra Tomar <tomer_iisc@...oo.com>, netdev@...r.kernel.org,
	davem@...emloft.net, Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH] net-next: Fix __inet_inherit_port() to correctly
	increment bsockets and num_owners

On Mon, Nov 29, 2010 at 03:51:02PM +0300, Evgeniy Polyakov wrote:
> On Mon, Nov 29, 2010 at 12:39:09PM +0000, Jarek Poplawski (jarkao2@...il.com) wrote:
> > >> inet sockets corresponding to passive connections are added to the bind hash
> > >> using ___inet_inherit_port(). These sockets are later removed from the bind 
> > >> hash using __inet_put_port(). These two functions are not exactly symmetrical. 
> > >> __inet_put_port() decrements hashinfo->bsockets and tb->num_owners, whereas 
> > >> ___inet_inherit_port() does not increment them. This results in both of these 
> > >> going to -ve values.
> > >>
> > >> This patch fixes this by calling inet_bind_hash() from ___inet_inherit_port(),
> > >> which does the right thing.
> > >>
> > >> 'bsockets' and 'num_owners' were introduced by commit a9d8f9110d7e953c 
> > >> (inet: Allowing more than 64k connections and heavily optimize bind(0))
> > > 
> > > Yup, things changed from that simple patch a lot.
> > > Thanks for fixing it up.
> > > Ack.
> > 
> > Probably I miss something, but since bsockets is increased by each
> > passive connection now, it seems it will trigger "hash table is full"
> > too early?
> 
> Why would it? bsockets and num_owners are supposed to be increased for each
> new socket added into the table, and are used as a hint to find a bucket with
> the smallest number of sockets in it.
> 
> Hash table insertion did not change, only bucket selection algorithm got
> a hint.

Evgeniy & Eric,

But it's compared to the numer of available port numbers in
inet_csk_get_port():

     "if (atomic_read(&hashinfo->bsockets) > (high - low) + 1)"

Can't you have bsockets higher than this with only one port used?

Jarek P.
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