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

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Date:	Tue, 13 Apr 2010 20:31:03 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Michael S. Tsirkin" <mst@...hat.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

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 ?

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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