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Article #81Enforcing asymmetric TCP MSS?
From: Eric Lee
Date: Tue, 10 May 2011 08:46
Date: Tue, 10 May 2011 08:46
24 lines
1530 bytes
1530 bytes
Hi, I'm trying to use scrub max-mss rules to create asymmetric MSS's. Is this supported? So far, I haven't got it to work (hence my post here). The machine is running OpenBSD 4.9 with 2 network cards. I have been trying things like: match out on $ext proto tcp scrub(max-mss 1000) flags S/SA match in on $ext proto tcp scrub(max-mss 500) flags SA/SA Scrubbing on the other interface doesn't seem to work either. match out on $int proto tcp scrub(max-mss 500) flags SA/SA client <--> pf gateway <--> internet With a sniffer on the client link and the internet link, -client sends large MSS on initial syn (> 1000) -pf scrubs MSS to 1000 on initial syn -pf receives large MSS on syn+ack (> 1000) -pf scrubs MSS to 1000 in syn+ack reply to client Thanks!
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X-Google-Thread: ff4ef,344061a51fc8e357,start X-Google-NewGroupId: yes X-Google-Attributes: gidbffa70e3,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Path: arc1-ca.pugleaf.net!g2news2.google.com!news2.google.com!npeer01.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!spln!newsgate.newsguy.com!newsp.newsguy.com!mdrn From: elee25@gmail.com (Eric Lee) Newsgroups: bit.listserv.openbsd-pf Subject: Enforcing asymmetric TCP MSS? Date: 10 May 2011 01:46:46 -0700 Organization: None Lines: 24 Message-ID: <BANLkTi=g-V5DdnpOhgSTCC4Na2RQZb47CA@mail.gmail.com> NNTP-Posting-Host: localhost.newsguy.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 NNTP-Posting-Date: 10 May 2011 08:46:46 GMT