Date: Thu, 29 Jun 2017 10:21:30 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 220351] Path MTU discovery works only after resetting an internal interface MTU (mpd5, ng_nat, ipfw) Message-ID: <bug-220351-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D220351 Bug ID: 220351 Summary: Path MTU discovery works only after resetting an internal interface MTU (mpd5, ng_nat, ipfw) Product: Base System Version: 11.0-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: la5lbtyi@aon.at Scenario: =3D=3D=3D=3D=3D=3D=3D=3D=3D I am using the following setup to connect a home network to the ISP: - mpd5 with "set iface enable nat" (so that mpd5 uses ng_nat) - ipfw - RFC1918 internal address range - FreeBSD 11.0 as border router running mpd5 and ipfw - FreeBSD 11.0 internal machine. - The internal network is wired Ethernet (100baseTX for the border router, 1000baseT for the internal machine), MTU 1500. Due to this setup, ipfw sees only the NATted addresses and is not concerned with NATting itself. Ipfw is configured to allow icmptypes 0,3,4,11,12 in and 3,8,11,12 out. Recently, the provider changed from PPPoA to PPPoE. This means that now the= MTU on the link to the provider is 1492 instead of 1500. In mpd5, I now have 's= et link mtu 1492; set link mru 1492'. Before that change, the problem described below in this PR did not occur. Scenario 1 (good): =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Running svn, git, and rsync from the border router to machines on the Inter= net works. Scenario 2 (problem): =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Running svn, git, and rsync from the internal machine to machines on the Internet nearly never works (maybe one out of 20). However, if I manually set the internal machine's Ethernet I/F MTU to 1492 = and immediately thereafter reset it to 1500 all subsequent connections work flawlessly (ifconfig <if> mtu 1492; ifconfig <if> mtu 1500). Expected result: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Svn, git, and rsync connections from the internal machine to machines on the Internet should work right after boot. -- Martin --=20 You are receiving this mail because: You are the assignee for the bug.=
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