Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use

From	Lawrence D’Oliveiro <ldo@nz.invalid>
Newsgroups	comp.os.linux.misc
Subject	Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use
Date	2025-08-31 03:25 +0000
Organization	A noiseless patient Spider
Message-ID	<1090fb5$30f6e$1@dont-email.me> (permalink)
References	(16 earlier) <108o94p$10pj9$8@dont-email.me> <108p4m2$173fr$1@dont-email.me> <108qtsm$1n18s$5@dont-email.me> <20250829081008.00004d8a@gmail.com> <108sqqi$25aq9$1@dont-email.me>

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On Fri, 29 Aug 2025 19:16:50 +0100, Mike Scott wrote:

> Oh - the problem in hand. No doubt it's easy when you know: single
> interface, allow all lan traffic, block wan inbound to port 22,
> redirect wan inbound on port 12345 to 22 and pass. Block wan inbound
> otherwise. If anyone has a config snippet to do this, I'd be very
> grateful.

Look at the stages of application of filter hooks here
<https://wiki.nftables.org/wiki-nftables/index.php/Netfilter_hooks>:
there is “ingress”, followed by “prerouting”, followed by “input”.

The obvious place to block incoming packets for port 22 would be
either “ingress” or “prerouting”; you should be able, at the same
stage or a later one, to remap ones destined for port 12345 so they go
to port 22, after the block.

<https://wiki.nftables.org/wiki-nftables/index.php/Mangling_packet_headers>

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Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Mike Scott <usenet.16@scottsonline.org.uk.invalid> - 2025-08-27 06:56 +0100
  Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-28 00:50 +0000
    Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Mike Scott <usenet.16@scottsonline.org.uk.invalid> - 2025-08-28 09:40 +0100
      Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-29 00:56 +0000
        Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use John Ames <commodorejohn@gmail.com> - 2025-08-29 08:10 -0700
          Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Mike Scott <usenet.16@scottsonline.org.uk.invalid> - 2025-08-29 19:16 +0100
            Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2025-08-30 16:59 +0300
              Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Mike Scott <usenet.16@scottsonline.org.uk.invalid> - 2025-08-30 18:45 +0100
                Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2025-08-31 21:24 +0300
                Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Mike Scott <usenet.16@scottsonline.org.uk.invalid> - 2025-09-01 17:02 +0100
            Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-31 03:25 +0000
          Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-30 06:34 +0000
            Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Nuno Silva <nunojsilva@invalid.invalid> - 2025-08-30 08:39 +0100
              Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use The Natural Philosopher <tnp@invalid.invalid> - 2025-08-30 08:45 +0100
              Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Harold Stevens <wookie@trixie.localdomain> - 2025-08-30 05:37 -0500
                Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use John Ames <commodorejohn@gmail.com> - 2025-09-02 09:59 -0700
                Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Harold Stevens <wookie@aspen.localdomain> - 2025-09-02 12:59 -0500
              Re: Yes, You Need A Firewall On Linux - Here’s Why And Which To Use Richard Kettlewell <invalid@invalid.invalid> - 2025-08-30 17:48 +0100

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