From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Savchenko Subject: Re: [BUG] Kernel recieves DNS reply, but doesn't deliver it to a waiting application Date: Mon, 4 Feb 2013 17:39:32 +0400 Message-ID: <20130204173932.bad780bc.bircoph@gmail.com> References: <20121003232548.eb6b6b22.bircoph@gmail.com> <20121013163639.87abca00.bircoph@gmail.com> <1350135860.21172.14606.camel@edumazet-glaptop> <20121014031119.a60263d6.bircoph@gmail.com> <20121021032543.09d1844f.bircoph@gmail.com> <1350823941.13333.2167.camel@edumazet-glaptop> <20121022073636.98462bc6.bircoph@gmail.com> <1350888489.8609.322.camel@edumazet-glaptop> <20121023012759.ca7f91d6.bircoph@gmail.com> <20121212122716.1e71f644.bircoph@gmail.com> <20121223150627.d7ebcf6a.bircoph@gmail.com> <1356718263.21409.430.camel@edumazet-glaptop> <20130116203644.8eb2a16f.bircoph@gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pgp-signature"; micalg="PGP-SHA1"; boundary="Signature=_Mon__4_Feb_2013_17_39_32_+0400_jlc=xTE.uE753apn" Cc: netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from mail-la0-f46.google.com ([209.85.215.46]:65282 "EHLO mail-la0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750946Ab3BDNj6 (ORCPT ); Mon, 4 Feb 2013 08:39:58 -0500 Received: by mail-la0-f46.google.com with SMTP id fq12so4503493lab.5 for ; Mon, 04 Feb 2013 05:39:56 -0800 (PST) In-Reply-To: <20130116203644.8eb2a16f.bircoph@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: --Signature=_Mon__4_Feb_2013_17_39_32_+0400_jlc=xTE.uE753apn Content-Type: multipart/mixed; boundary="Multipart=_Mon__4_Feb_2013_17_39_32_+0400_P_BPTZBV_NBYwd+V" --Multipart=_Mon__4_Feb_2013_17_39_32_+0400_P_BPTZBV_NBYwd+V Content-Type: text/plain; charset=US-ASCII Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello, On Wed, 16 Jan 2013 20:36:44 +0400 Andrew Savchenko wrote: > On Fri, 28 Dec 2012 10:11:03 -0800 Eric Dumazet wrote: [...] > > Thanks a lot ! > >=20 > > I see strange drops in dev_hard_start_xmit() > >=20 > > l2tp needs some care. > >=20 > > Please try the following patch, as skb_cow_head() API > > doesnt really ease skb->truesize exact tracking anyway, better not mess > > with it.=20 >=20 > Sorry for the delay, but I was able to reboot kernel only today. > Your patch is applied on top of the 3.7.2 vanilla kernel. >=20 > l2tp works fine and /proc/net/udp tx_queue values are normal now, see > attached /prot/net/udp output. This is a good hint that problem is > probably solved, but we need to wait at least several weeks to be > sure. With 16-days uptime system works fine. Also I was able to reproduce this bug on another box: an embedded system running openwrt with 3.7.5 kernel with openl2tpd client and dnsmasq server. Due to limited memory resources this bug happened to be easily reproducible: several thousands of dns queries were sufficient to reproduce this bug. Full debug on embedded box was not possible due to constrained resources, but bug appearance was the same and /proc/net/udp is apparently broken (see attached log). I applied your patch on openwrt's 3.7.5 kernel and it fixed the bug on this box too. So we've found a solution and I'm looking forward for it in the main kernel :) Best regards, Andrew Savchenko --Multipart=_Mon__4_Feb_2013_17_39_32_+0400_P_BPTZBV_NBYwd+V Content-Type: application/octet-stream; name="proc.net.udp" Content-Disposition: attachment; filename="proc.net.udp" Content-Transfer-Encoding: base64 IyBjYXQgL3Byb2MvbmV0L3VkcAogIHNsICBsb2NhbF9hZGRyZXNzIHJlbV9hZGRyZXNzICAgc3Qg dHhfcXVldWUgcnhfcXVldWUgdHIgdG0tPndoZW4gcmV0cm5zbXQgICB1aWQgIHRpbWVvdXQgaW5v ZGUgcmVmIHBvaW50ZXIgZHJvcHMgICAgICAgICAgICAgCiAgIDQyOiAwMDAwMDAwMDo3QjJBIDAw MDAwMDAwOjAwMDAgMDcgRkZGRkZGQjA6MDAwMDAwMDAgMDA6MDAwMDAwMDAgMDAwMDAwMDAgNjU1 MzQgICAgICAgIDAgNjIzOSAyIDgxNmJiNzYwIDEgICAgICAgICAgICAgICAgICAKICAgNTM6IDAw MDAwMDAwOjAwMzUgMDAwMDAwMDA6MDAwMCAwNyAwMDAwMDAwMDowMDAwMDAwMCAwMDowMDAwMDAw MCAwMDAwMDAwMCAgICAgMCAgICAgICAgMCAxNDc2IDIgODFiNmU0NDAgMCAgICAgICAgICAgICAg ICAgIAogICA2NzogMDAwMDAwMDA6MDA0MyAwMDAwMDAwMDowMDAwIDA3IDAwMDAwMDAwOjAwMDAw MDAwIDAwOjAwMDAwMDAwIDAwMDAwMDAwICAgICAwICAgICAgICAwIDE0NzEgMiA4MWI2ZTIyMCAw ICAgICAgICAgICAgICAgICAgCiAgIDc2OiAwMDAwMDAwMDoxQjRDIDAwMDAwMDAwOjAwMDAgMDcg RkZGRkZGQjA6MDAwMDAwMDAgMDA6MDAwMDAwMDAgMDAwMDAwMDAgNjU1MzQgICAgICAgIDAgNjIy NSAyIDgxNmJhY2MwIDEgICAgICAgICAgICAgICAgICAKICAgOTU6IDAwMDAwMDAwOjE2NUYgMDAw MDAwMDA6MDAwMCAwNyBGRkZGRkZCMDowMDAwMDAwMCAwMDowMDAwMDAwMCAwMDAwMDAwMCA2NTUz NCAgICAgICAgMCA2MjIxIDIgODE2YmE4ODAgMSAgICAgICAgICAgICAgICAgIAogIDEwMTogMEEz NDE4MkU6QUU2NSAwQTMyMDAxNDowNkE1IDAxIDAwMDAwMDAwOjAwMDAwMDAwIDAwOjAwMDAwMDAw IDAwMDAwMDAwICAgICAwICAgICAgICAwIDE1MzggNCA4MWI2ZWNjMCAwICAgICAgICAgICAgICAg ICAgCiAgMTIzOiAwMDAwMDAwMDowMDdCIDAwMDAwMDAwOjAwMDAgMDcgMDAwMDAwMDA6MDAwMDAw MDAgMDA6MDAwMDAwMDAgMDAwMDAwMDAgICAgIDAgICAgICAgIDAgMTUzMCAyIDgxYjZlODgwIDAg ICAgICAgICAgICAgICAgICAKICAxMjY6IDAwMDAwMDAwOjg0N0UgMDAwMDAwMDA6MDAwMCAwNyBG RkZGRkZCMDowMDAwMDAwMCAwMDowMDAwMDAwMCAwMDAwMDAwMCA2NTUzNCAgICAgICAgMCA2MjIz IDIgODE2YmFhYTAgMSAgICAgICAgICAgICAgICAgIAogIDE1MzogMDAwMDAwMDA6Q0Y5OSAwMDAw MDAwMDowMDAwIDA3IEZGRkZGRkIwOjAwMDAwMDAwIDAwOjAwMDAwMDAwIDAwMDAwMDAwIDY1NTM0 ICAgICAgICAwIDYyMzMgMiA4MTZiYjU0MCAxICAgICAgICAgICAgICAgICAgCiAgMTYzOiAwMDAw MDAwMDowOUEzIDAwMDAwMDAwOjAwMDAgMDcgRkZGRkZGQjA6MDAwMDAwMDAgMDA6MDAwMDAwMDAg MDAwMDAwMDAgNjU1MzQgICAgICAgIDAgNjIyNyAyIDgxNmJhZWUwIDEgICAgICAgICAgICAgICAg ICAKICAxNjU6IDAwMDAwMDAwOjA2QTUgMDAwMDAwMDA6MDAwMCAwNyAwMDAwMDAwMDowMDAwMDAw MCAwMDowMDAwMDAwMCAwMDAwMDAwMCAgICAgMCAgICAgICAgMCAxNTIzIDIgODFiNmU2NjAgMCAg ICAgICAgICAgICAgICAgIAogIDE4NDogMDAwMDAwMDA6NzBCOCAwMDAwMDAwMDowMDAwIDA3IEZG RkZGRkIwOjAwMDAwMDAwIDAwOjAwMDAwMDAwIDAwMDAwMDAwIDY1NTM0ICAgICAgICAwIDYyMzEg MiA4MTZiYjMyMCAxICAgICAgICAgICAgICAgICAgCiAgMjI2OiAwMDAwMDAwMDpDQ0UyIDAwMDAw MDAwOjAwMDAgMDcgRkZGRkZGQjA6MDAwMDAwMDAgMDA6MDAwMDAwMDAgMDAwMDAwMDAgNjU1MzQg ICAgICAgIDAgNjIyOSAyIDgxNmJiMTAwIDEK --Multipart=_Mon__4_Feb_2013_17_39_32_+0400_P_BPTZBV_NBYwd+V-- --Signature=_Mon__4_Feb_2013_17_39_32_+0400_jlc=xTE.uE753apn Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iEYEARECAAYFAlEPuiUACgkQ2anJBBcsZw36AwCgucMpj/ov/L2Ch1kfSNfgqjOd gPQAoK2zzXzQpoPjoI8n4uSdVhwd8ul+ =GwWK -----END PGP SIGNATURE----- --Signature=_Mon__4_Feb_2013_17_39_32_+0400_jlc=xTE.uE753apn--