From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Siemon Subject: PMTU problem with >2.6.38 and IPIP tunnels Date: Sat, 23 Jul 2011 21:40:49 -0400 Message-ID: <1311471668.10268.12.camel@ganymede> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-nZ6uHYj7HlQDMSt0a5Ie" To: netdev@vger.kernel.org Return-path: Received: from alpha.coverfire.com ([69.41.199.58]:53270 "EHLO alpha.coverfire.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751938Ab1GXCnZ (ORCPT ); Sat, 23 Jul 2011 22:43:25 -0400 Received: from [192.168.88.98] (milv-rb-2-stat-199-68.nblk1.cyg.net [69.41.199.68]) (authenticated bits=0) by alpha.coverfire.com (8.14.4/8.14.4) with ESMTP id p6O1f726010275 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO) for ; Sat, 23 Jul 2011 21:41:08 -0400 Sender: netdev-owner@vger.kernel.org List-ID: --=-nZ6uHYj7HlQDMSt0a5Ie Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable I'm running into some MTU related problems with kernels newer than 2.6.38. I've tried bisecting and it appears the problem was introduced between 2.6.39rc2 and rc3 but I'm not 100% certain because the problem does not always present itself immediately. I am certain this does not occur with 2.6.38.8. I tunnel all of my home network traffic over an IPIP tunnel. My Internet access is DSL based so there's a PPPoE connection as well. Both ends of the IPIP tunnel are Linux. When the gateway is first booted with the problem kernel everything is fine. Using 'show ip route cache' I see MTU entries with the correct values. After a short period the MTU on all the routes starts dropping in what often appears to be 20 byte increments. show ip route cache | egrep -i mtu cache expires 435sec ipid 0x28de mtu 712 iif eth1 cache expires 542sec ipid 0x66e8 mtu 672 iif eth1 Until eventually all routes show a MTU of 552. I'd be happy to run tests if anyone has an idea of what is causing this. --=-nZ6uHYj7HlQDMSt0a5Ie Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iQIcBAABCAAGBQJOK3ghAAoJEJKXGLoTP2w+pjoQAImEGOiSdhUKF/NYbWZ5/0OQ Qj+0NFGyX9ejvMJ4lc8gh94eEKx5bpyv3xuBgsndWr002p88hnpB7pQT71IgC+pu 23VkI791bo0k1Nr7ZKqT1+YOVthCG5a5+2spe/YtRsGPFbtsWPpjK08kPiRkLqYY lNukG2XvpWHRXikyc3yLkCgShQhh1jmqMUQQXpwa2oUr46ocyNLHPomAB6OZJnQP NPn3vafjlemUgQZb6gaRoaXHzPT9k3wimdLwGK1Dtb9K9gUgfp9dcWEI9kTTTk3A OV+9xS6pMWtU5lC1OQ3sslsDNxs1csqaEBZQLS/VKIpo0u+kCNqipIorwIl89A3U 7BnXE28ERNzdY+S1uk5Cn4/nNJB7nHzjqcv33Q4XgfKKqMCsgGDO/HPQedNW6OwZ HcSpph0C24pMhDvwo/BH4X9jfj1JWeGx4eC7JUyfvItaJMeWhdWe+vG579EplfMH QGrjC17y/mXE2EZpHrrfwBXARPqIV/RTvUt77pNjZE8zyMCXM8lG7QvretT3Xlti jH6CWu1FnmwmKbTSbo68nOgP7rQRV5kYYLWeEEjegHmm6GSRFGQHmie0/lS9Z+Hs YU/nU7Uy02YA2ROmVxEU5r0FQE+rew2imkotThQsGzyHcGfr4Dwm8AdTxk/J5JXQ q4t73nGaCpZkRp6F2vR/ =yp16 -----END PGP SIGNATURE----- --=-nZ6uHYj7HlQDMSt0a5Ie--