On Thu, May 28, 2009 at 2:28 PM, Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx> wrote: > On Wed, 27 May 2009, Saatvik Agarwal wrote: > >> For my research project in school, I am trying to establish TCP >> connections when both hosts are behind full-cone NATs using TCP's >> simultaneous open functionality. Unfortunately, it seems that iptables >> does not support TCP simultaneous open. For my test environment, I >> simulate a full-cone NAT using iptables. My iptables rule is exactly >> as follows: >> >> iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE > > That rule cannot simulate full-cone NAT, because netfilter implements > port-restricted cone NAT. I agree to most of stuff that you have said but the above statement of "port-restricted cone NAT" confuses me. If we look at different types of NATs as mentioned here www.crfreenet.org/~martin/referaty/stun/naty.pdf , i think the netfilter implementation is really a symmetric NAT. Iam I missing some thing? > >> According to the BEHAVE requirements outlined in IETF RFC 5382, TCP >> simultaneous open must be supported by "well behaved NATs". So is >> there a mistake in my rules or does iptables not support simultaneous >> open? > > The connection tracking subsystem does not support TCP simultaneous open. > > As far as I'm concerned, I do not care whatever RFC is created in trying > to push NAT over its limits - that is just a totally wrong track. NAT was > invented solely to slow down the depletion of the IPv4 address space in > the hope to give more time introducing and *deploying* IPv6 world-wide. > And everyone was fully aware that NAT breaks one of the key concempts of > IP, the end-to-end connectivity. These "NAT behavioral requirements" RFCs > are the results of that breakage (and written exclusively from the point > of view of the application designers). > > It is no point trying to *put back* end-to-end connectivity on top of NAT > when the clear and straight solution is to go to IPv6. > > The end-to-end connectivity is the very reason why I refuse the idea to > implement NAT for IPv6 in netfilter. The damage what IPv4 NAT produced > hasn't taught us not to repeat the same mistake again, willingly? > > Best regads, > Jozsef > - > E-mail : kadlec@xxxxxxxxxxxxxxxxx, kadlec@xxxxxxxxxxxx > PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt > Address : KFKI Research Institute for Particle and Nuclear Physics > H-1525 Budapest 114, POB. 49, Hungary > -- > To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
