Date: Sun, 21 Feb 2016 19:25:12 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: Julian Elischer <julian@freebsd.org> Cc: galtsev@kicp.uchicago.edu, freebsd-net@freebsd.org Subject: Re: gateway machine port redirect question Message-ID: <alpine.BSF.2.20.1602211917550.3886@wonkity.com> In-Reply-To: <56CA5519.4080000@freebsd.org> References: <43887.128.135.52.6.1456021321.squirrel@cosmo.uchicago.edu> <56CA5519.4080000@freebsd.org>
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On Sun, 21 Feb 2016, Julian Elischer wrote: > On 20/02/2016 6:22 PM, Valeri Galtsev wrote: >> Dear Experts, >> >> I'm one of Linux refugees who several years ago migrated majority of >> servers from Linux to FreeBSD and is happy since. When recently I needed >> to set up gateway (Firewall + NAT) machine, I set up FreeBSD 10.2 on it, >> used ipwf and natd, and all works well, machines behind gateway on LAN can >> happily reach real network. I hit one snag later though: When I tried to >> redirect TCP traffic on some port to machine on internal private network >> behind gateway, whatever I do doesn't work. >> >> Could somebody point to simple example (it doesn't matter which components >> are involved, I don't feel married to ipfw and natd) for FreeBSD 10.2 that >> makes the machine gateway, and one of the ports of traffic coming from >> public network is redirected to machine on private network behind gateway. >> Something I can reproduce that works, which I then will gradually convert >> into what I need. Other way around: adding redirection to already working >> (and a bit sophisticated) gateway I set up appears to be beyond my mental >> abilities: a couple of weeks of frustration confirm it to me. >> >> I really do not want to go back to Linux to do this, even though I feel I >> can do it based on Linux in a course of an hour or two - I've set up a few >> of them in the past using Linux, that's the longest it took me in my >> recollection. >> > this CAN be done but it gets tricky. > > usually we do NAT on the external interface. the trouble is that you don't > want that traffic to go through the external interface, but to get routed > back in. > you really should add a special rule group that traps the packets as they > come in on the internal interface and send them to nat if they are destined > for the other internal machine. (and the return packets). > > I have never done this so when you work it out let us know :-) I understood this to be just a standard redirect from the outside interface to a server inside the LAN. To redirect inside traffic to that same machine takes another redirect and NAT rule: nat on $int_if proto tcp from $internal_net to $webserver port 80 -> $int_if rdr on $int_if proto tcp from $internal_net to $internal_addr port 80 -> $webserver port 80 Adapted from my rules for a different type of server, so might need adjustment. Again, this is PF.
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