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Subject: Re: [PATCH] new UDPCP Communication Protocol
From: Stefani Seibold <stefani@seibold.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        davem@davemloft.net, netdev@vger.kernel.org, shemminger@vyatta.com,
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Date: Sun, 02 Jan 2011 23:55:17 +0100
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Am Sonntag, den 02.01.2011, 23:49 +0100 schrieb Eric Dumazet:
> Le dimanche 02 janvier 2011 à 23:39 +0100, stefani@seibold.net a écrit :
> > +
> > +/*
> > + * Create a new destination descriptor for the given IPV4 address and port
> > + */
> > +static struct udpcp_dest *new_dest(struct sock *sk, __be32 addr, __be16 port)
> > +{
> > +	struct udpcp_dest *dest;
> > +	struct udpcp_sock *usk = udpcp_sk(sk);
> > +
> > +	if (usk->connections >= udpcp_max_connections)
> > +		return NULL;
> > +
> > +	dest = kzalloc(sizeof(*dest), sk->sk_allocation);
> > +
> > +	if (dest) {
> > +		usk->connections++;
> > +		skb_queue_head_init(&dest->xmit);
> > +		dest->addr = addr;
> > +		dest->port = port;
> > +		dest->ackmode = UDPCP_ACK;
> > +		list_add_tail(&dest->list, &usk->destlist);
> > +	}
> > +
> > +	return dest;
> > +}
> > +
> 
> Hmm, so 'connections' is increased, never decreased.
> 
> This seems a fatal flaw in this protocol, since a malicious user can
> easily fill the list with garbage, and block regular communications.

You are right, there is now way to detect which connection is no longer
needed. I have not designed this protocol, so i cannot fix it. 

But in our environment this will be used together with an firewall
and/or ipsec. In this case it it safe.