netdev - Re: [PATCH] tun: orphan an skb on tx

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Message-ID: <20100413202548.GA3582@redhat.com>
Date:	Tue, 13 Apr 2010 23:25:48 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Jan Kiszka <jan.kiszka@...mens.com>,
	"David S. Miller" <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	Paul Moore <paul.moore@...com>,
	David Woodhouse <David.Woodhouse@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>
Subject: Re: [PATCH] tun: orphan an skb on tx

On Tue, Apr 13, 2010 at 08:31:03PM +0200, Eric Dumazet wrote:
> Le mardi 13 avril 2010 à 20:39 +0300, Michael S. Tsirkin a écrit :
> 
> > > When a socket with inflight tx packets is closed, we dont block the
> > > close, we only delay the socket freeing once all packets were delivered
> > > and freed.
> > > 
> > 
> > Which is wrong, since this is under userspace control, so you get
> > unkillable processes.
> > 
> 
> We do not get unkillable processes, at least with sockets I was thinking
> about (TCP/UDP ones).
> 
> Maybe tun sockets can behave the same ?

Looks like that's what my patch does: ip_rcv seems to call
skb_orphan too.

> Herbert Acked your patch, so I guess its OK, but I think it can be
> dangerous.
> Anyway my feeling is that we try to add various mechanisms to keep a
> hostile user flooding another one.
> 
> For example, UDP got memory accounting quite recently, and we added
> socket backlog limits very recently. It was considered not needed few
> years ago.
> 



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