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Date: Mon, 27 Jan 2025 21:37:29 +0100
From: Marc SCHAEFER <schaefer@alphanet.ch>
To: netfilter@vger.kernel.org
Subject: Generic map, also with L4 protocol
Message-ID: <Z5fuieMugg4fcNKR@alphanet.ch>
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Hello,

for dynamic DNAT, I use:

   map multihoming_ext {
      type ipv4_addr . inet_service : ipv4_addr . inet_service
      elements = {
         46.140.72.218 . 8080  : 192.168.202.10 . 80,
         193.72.186.130 . 8080 : 192.168.202.10 . 80
      }
   }

   chain multihoming_prerouting {
      type nat hook prerouting priority -100; policy accept;

      dnat ip addr . port to ip daddr . tcp dport map @multihoming_ext
   }

This seems to DNAT correctly as wanted:

   46.140.72.218:8080 is DNATted to 192.168.202.10:80
and
   193.72.186.130:8080 is DATted to 192.168.202.10:80

To make it even more generic and dynamic, I would like to have also the
protocol in the map, something like:

   map multihoming_ext {
      type ipv4_addr . inet_proto . inet_service : ipv4_addr . inet_service
      elements = {
         46.140.72.218 . tcp . 8080  : 192.168.202.10 . 80,
         193.72.186.130 . tcp . 8080 : 192.168.202.10 . 80
      }
   }

However I have no idea how to modify the DNAT line itself to
get the L4 protocol from the map correctly.

Do you have any idea?

Thank you.