Date: Wed, 01 Jul 2015 22:02:53 +0300 From: Lev Serebryakov <lev@FreeBSD.org> To: freebsd-ipfw@freebsd.org Subject: Re: keep-state and in-kernel NAT exposes local ip on external interface Message-ID: <5594395D.6050103@FreeBSD.org> In-Reply-To: <1435692039.18121.12.camel@yahoo.com> References: <1435692039.18121.12.camel@yahoo.com>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 30.06.2015 22:20, Georgios Amanakis via freebsd-ipfw wrote: It is good example for my changes :) All this "skipto / keep-state" magic is not understandable. > On FreeBSD 10.1p13 with two interfaces em0(internet) and em1(lan) I > can fish (tcpdump)packets on em0 which have escaped the in-kernel > NAT and have as source address an IP on the LAN. > > This should not happen and I can confirm that with pf this is not > the case. I have the following ipfw rules: > > nat: ipfw nat 123 config ip xxx.xxx.xxx.xxx same_ports reset > > 00100 reass ip from any to any in 00200 allow ip from any to any > via lo0 00300 allow ip from any to any via em1 00400 nat 123 ip > from any to any in recv em0 00500 check-state 00600 skipto 24000 ip > from any to me dst-port 80,443,22,500,4500,1194,993,8112 in recv > em0 keep-state 00700 skipto 24000 ip from any to any out xmit em0 > keep-state 00800 deny log ip from any to any 24000 nat 123 ip from > any to any out xmit em0 24100 allow ip from any to any > > Contrary to many online tutorials, including the example of the > handbook regarding NAT ( > https://www.freebsd.org/doc/handbook/firewalls-ipfw.html), when > one places the NAT rules with the opposite order (i.e. outbound > rule first and then the inbound rule) the problem disappears. > > i.e. ... 00400 nat 123 ip from any to any out xmit em0 ... 24000 > nat 123 ip from any to any in recv em0 ... > > Why is this happening? Any objections to reversing the order of the > NAT rules? _______________________________________________ > freebsd-ipfw@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-ipfw To > unsubscribe, send any mail to > "freebsd-ipfw-unsubscribe@freebsd.org" > - -- // Lev Serebryakov -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (MingW32) iQJ8BAEBCgBmBQJVlDldXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRGOTZEMUNBMEI1RjQzMThCNjc0QjMzMEFF QUIwM0M1OEJGREM0NzhGAAoJEOqwPFi/3EePkigQAMhJSo5UaDxrAz5RmMt1KjJX 5kXKXe35NLzI6J3bt/ZBBwmJSl1Z/17BEhTAMQmietAi5zVV8QD8DB+lq/jjvY3F TmADQ4O/b2Dml/Vgcg8fzv4Oai/fPENfNLZNItc/Hv9fxKtDUoxW3SehlTcti/DM 5VpIb0Td7o3WWEmtYMUHSvYIXpUQSr8IeE48Svd4dKJ7x7oJP11qpECa2vsDRJFc 8BM5jWWfJqfWcB//+G/9C9nT4DbTHhwrP4UkvZDwM2mc8xz5gzEtwXUDPle8Bgtb StHrMkrgZvGfGWd95dPVm3oTdhIVvv3KSNW47PCo/xRVz8ZQKog2N4QYrNIUzhbL Igmxus3VD4uwqr+3z+lB5lgUYMeB0pqnEihWGAQ15cwxNRlEEFOg/hGZTiNx9u88 2/UcK6up2jtxBTXy2Tf/CWL12PqnkDxsC2drZULDOR9P/XT3YcB++ie6Xz9iv7rt 3C8hOQ3B8LqAKfTP4LG2vh1uv4X6Vw7sfx3vpGXr3bQFaZt/odesI3/SiWaSmkNi bu6JKU2QnepLRrKObeggIap4SSRq7AKZiVa+O5R3HJFAhsFLutgHIYP1G7+BzHAX OCHRXgHiWDNNKa9tzUQgdS372kM+kP10vbY74TJ2dEL3Nwc9XehiasToEVfYhLin FG8VdsZZSi+wA8Pg3YbQ =kzTV -----END PGP SIGNATURE-----
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