From owner-freebsd-questions@freebsd.org Tue Jun 18 17:56:12 2019 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A238D15C432C for ; Tue, 18 Jun 2019 17:56:12 +0000 (UTC) (envelope-from karl@denninger.net) Received: from colo1.denninger.net (colo1.denninger.net [104.236.120.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 499C187804 for ; Tue, 18 Jun 2019 17:56:12 +0000 (UTC) (envelope-from karl@denninger.net) Received: from denninger.net (ip68-1-57-197.pn.at.cox.net [68.1.57.197]) by colo1.denninger.net (Postfix) with ESMTP id 3CD1A211080 for ; Tue, 18 Jun 2019 13:56:06 -0400 (EDT) Received: from [192.168.43.86] (unknown [172.56.21.82]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by denninger.net (Postfix) with ESMTPSA id 49704170DC7 for ; Tue, 18 Jun 2019 12:56:05 -0500 (CDT) Subject: Re: IPFW redirect to another port? To: freebsd-questions@freebsd.org References: <20190618165028.83C662015F9118@ary.qy> From: Karl Denninger Message-ID: Date: Tue, 18 Jun 2019 12:56:01 -0500 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <20190618165028.83C662015F9118@ary.qy> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms070105020402020603050607" X-Rspamd-Queue-Id: 499C187804 X-Spamd-Bar: ------ Authentication-Results: mx1.freebsd.org X-Spamd-Result: default: False [-6.98 / 15.00]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; REPLY(-4.00)[]; NEURAL_HAM_SHORT(-0.98)[-0.983,0] X-Content-Filtered-By: Mailman/MimeDel 2.1.29 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 18 Jun 2019 17:56:12 -0000 This is a cryptographically signed message in MIME format. --------------ms070105020402020603050607 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 6/18/2019 11:50 AM, John Levine wrote: > I would like to use ipfw to redirect incoming port 53 requests from a > few IP addresses to a different port, so I can use a custom DNS server > to answer them. I can figure out how to redirect their traffic to, > say, port 5553, but the responses come from 5553 which of course > doesn't work. > > Any suggestions about how to adjust the port numbers going both ways? = It's > fine if they screw up other traffic to those IPs. TIA. The easiest way to do this is likely with an in-kernel NAT entry with a=20 "redirect_port" stanza; that will "twist" packets going in both=20 directions.=C2=A0 The most-common use for this is to take something on th= e=20 external interface (e.g. 1.2.3.4:8080) and direct it at an internal host = on port 80 (e.g. 10.1.1.1:80); the "redirect_port" stanza allows for=20 both TCP and UDP redirection with both sides being translated. --=20 -- Karl Denninger /The Market-Ticker/ S/MIME Email accepted and preferred --------------ms070105020402020603050607 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC DdgwggagMIIEiKADAgECAhMA5EiKghDOXrvfxYxjITXYDdhIMA0GCSqGSIb3DQEBCwUAMIGL MQswCQYDVQQGEwJVUzEQMA4GA1UECAwHRmxvcmlkYTESMBAGA1UEBwwJTmljZXZpbGxlMRkw 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