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Groups > comp.os.linux.networking > #4823
| From | John Smith <12345@whatismyemailaddress.xyz> |
|---|---|
| Newsgroups | comp.os.linux.networking |
| Subject | Re: Forwarding a TCP connection |
| Date | 2021-03-14 23:13 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <s2m5bc$1vfp$1@gioia.aioe.org> (permalink) |
| References | <s2lqd7$1ljv$1@gioia.aioe.org> |
On Sun, 14 Mar 2021 20:07:04 +0000, John Smith wrote: > I have a Linux system A in my network where a TCP server is running at > port P. The details of this server are irrelevant beyond the fact that > it is a TCP server. > > What I would like to do is the following; > > I have another Linux system B in the same network. Would it be > possible to configure B so that when be receives a TCP connection > request on port B, the connection is silently and transparently > forwarded to A? That is, my goal is for B to act as man-in-the-middle, > totally transparent as far as B is concerned. > > Can this be done? Actually, I found out how to do it with iptables. Assuming that the internal network is the 192.168.0 network, one can create the following IP tables rules in B: iptables -t nat -A PREROUTING -i <nic> -p tcp --dport <port> -j DNAT --to-destination <A-ip-address>:<port> iptables -A FORWARD -i <nic> -d <A-ip-address> -p tcp --dport <port> -j ACCEPT iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -d <A-ip-address> -p tcp --dport <port> -j SNAT --to-source <B-ip-address> iptables -t nat -A POSTROUTING -o <nic> -d <A-ip-address> -p tcp --dport <port> -j SNAT --to-source <B-ip-address> where <nic>: The appropriate network interface in B. <port>: The port number. <A-ip-address>: The IP address of A. <B-ip-address>: The IP address of B. After doing this, when some other system in my network attempts to contact B at port P, the connection gets transparently forwarded to A at port P. This does look quite complicated for what it does. The thing is, I tried with simpler suggestions that I came across online, and couldn't get them to work. If anybody has a simpler set of rules that works, I'd be happy to learn about it.
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Forwarding a TCP connection John Smith <12345@whatismyemailaddress.xyz> - 2021-03-14 20:07 +0000
Re: Forwarding a TCP connection "Carlos E.R." <robin_listas@es.invalid> - 2021-03-14 22:41 +0100
Re: Forwarding a TCP connection Richard Kettlewell <invalid@invalid.invalid> - 2021-03-14 22:02 +0000
Re: Forwarding a TCP connection "Carlos E.R." <robin_listas@es.invalid> - 2021-03-14 23:26 +0100
Re: Forwarding a TCP connection Richard Kettlewell <invalid@invalid.invalid> - 2021-03-14 22:46 +0000
Re: Forwarding a TCP connection Pascal Hambourg <pascal@plouf.fr.eu.org> - 2021-03-15 09:42 +0100
Re: Forwarding a TCP connection Jim Jackson <jj@franjam.org.uk> - 2021-03-14 22:03 +0000
Re: Forwarding a TCP connection "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2021-03-14 17:40 -0400
Re: Forwarding a TCP connection John Smith <12345@whatismyemailaddress.xyz> - 2021-03-14 23:23 +0000
Re: Forwarding a TCP connection dyrmak <dyrmak@quelite.terre.invalid> - 2021-03-15 17:49 +0000
Re: Forwarding a TCP connection Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-15 20:14 +0200
Re: Forwarding a TCP connection "Carlos E.R." <robin_listas@es.invalid> - 2021-03-15 23:28 +0100
Re: Forwarding a TCP connection Jorgen Grahn <grahn+nntp@snipabacken.se> - 2021-03-15 23:15 +0000
Re: Forwarding a TCP connection dyrmak <dyrmak@orange.fr.invalid> - 2021-03-16 07:59 +0000
Re: Forwarding a TCP connection Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-16 11:16 +0200
Re: Forwarding a TCP connection Jim Jackson <jj@franjam.org.uk> - 2021-03-16 14:53 +0000
Re: Forwarding a TCP connection "Carlos E.R." <robin_listas@es.invalid> - 2021-03-16 03:21 +0100
Re: Forwarding a TCP connection Jim Jackson <jj@franjam.org.uk> - 2021-03-16 14:49 +0000
Re: Forwarding a TCP connection Johann Beretta <beretta@nun-ya-bizness.com> - 2021-05-28 13:19 -0700
Re: Forwarding a TCP connection Grant Taylor <gtaylor@tnetconsulting.net> - 2021-05-28 16:20 -0600
Re: Forwarding a TCP connection Johann Beretta <beretta@nun-ya-bizness.com> - 2021-05-28 13:15 -0700
Re: Forwarding a TCP connection Grant Taylor <gtaylor@tnetconsulting.net> - 2021-05-28 16:23 -0600
Re: Forwarding a TCP connection Marc Haber <mh+usenetspam1118@zugschl.us> - 2021-05-29 18:42 +0200
Re: Forwarding a TCP connection Grant Taylor <gtaylor@tnetconsulting.net> - 2021-05-29 19:29 -0600
Re: Forwarding a TCP connection Marc Haber <mh+usenetspam1118@zugschl.us> - 2021-05-30 12:08 +0200
Re: Forwarding a TCP connection Grant Taylor <gtaylor@tnetconsulting.net> - 2021-05-31 22:43 -0600
Re: Forwarding a TCP connection Marc Haber <mh+usenetspam1118@zugschl.us> - 2021-06-01 08:51 +0200
Re: Forwarding a TCP connection Johann Beretta <beretta@nun-ya-bizness.com> - 2021-03-24 19:30 -0700
Re: Forwarding a TCP connection Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-25 16:35 +0200
Re: Forwarding a TCP connection Pascal Hambourg <pascal@plouf.fr.eu.org> - 2021-03-25 20:03 +0100
Re: Forwarding a TCP connection Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-25 21:34 +0200
Re: Forwarding a TCP connection Pascal Hambourg <pascal@plouf.fr.eu.org> - 2021-03-25 21:54 +0100
Re: Forwarding a TCP connection Johann Beretta <beretta@nun-ya-bizness.com> - 2021-03-29 13:45 -0700
Re: Forwarding a TCP connection Johann Beretta <beretta@nun-ya-bizness.com> - 2021-03-29 13:43 -0700
Re: Forwarding a TCP connection Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2021-03-30 20:26 +0300
Re: Forwarding a TCP connection Johann Beretta <beretta@nun-ya-bizness.com> - 2021-03-30 22:49 -0700
Re: Forwarding a TCP connection Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2021-03-31 16:29 +0000
Re: Forwarding a TCP connection John Smith <12345@whatismyemailaddress.xyz> - 2021-03-14 23:13 +0000
Re: Forwarding a TCP connection Jorgen Grahn <grahn+nntp@snipabacken.se> - 2021-03-15 06:59 +0000
Re: Forwarding a TCP connection Pascal Hambourg <pascal@plouf.fr.eu.org> - 2021-03-15 09:48 +0100
Re: Forwarding a TCP connection John Smith <12345@whatismyemailaddress.xyz> - 2021-03-15 13:44 +0000
Re: Forwarding a TCP connection Pascal Hambourg <pascal@plouf.fr.eu.org> - 2021-03-15 20:49 +0100
Re: Forwarding a TCP connection John Smith <12345@whatismyemailaddress.xyz> - 2021-03-15 21:10 +0000
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