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[lvs-users] LVS-DR: director cuts packets with payload size > MSS (1460)

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: [lvs-users] LVS-DR: director cuts packets with payload size > MSS (1460)
From: "Дениска-редиска" <slim@xxxxxxxx>
Date: Thu, 11 Jul 2013 17:17:20 +0300
   hello,
   i have strange issue with LVS in direct routing mode - Director forwards
   between interfaces packets with payload < 1460 only
   see below dumps from two interfaces on same box where eth1 is incoming
   interface where VIP is up, and eth0 is outgoing interface to real-servers.
   A packet with id 11270 (length 2960) is present in incoming traffic but
   absent in outgoing. Same with packet id 11279
   why this may happens ?
   I am running kernel 3.8.13 without conntrack.
   look what happens on interfaces as tcpdump shows:
   eth1 is incoming interface where VIP 10.1.1.60 is up:

   (virtual) foto1 ~ #  tcpdump -i eth1 -vv -n port 80 and host 10.1.1.145


   tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size 68
   bytes

   16:38:34.896032 IP (tos 0x0, ttl 128, id 11268, offset 0, flags [DF], proto
   TCP    (6),    length   52)   10.1.1.145.63094   >   10.1.1.60.80:   S
   1211165489:1211165489(0) win 8192 <mss 1460,[|tcp]>

   16:38:34.896843 IP (tos 0x0, ttl 128, id 11269, offset 0, flags [DF], proto
   TCP  (6),  length 40) 10.1.1.145.63094 > 10.1.1.60.80: ., cksum 0x6192
   (correct), 1211165490:1211165490(0) ack 2881536955 win 64240

   16:38:34.896978 IP (tos 0x0, ttl 128, id 11270, offset 0, flags [DF], proto
   TCP (6), length 2960) 10.1.1.145.63094 > 10.1.1.60.80: . 0:2920(2920) ack 1
   win 64240

   16:38:35.206653 IP (tos 0x0, ttl 128, id 11273, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 0:1460(1460) ack 1
   win 64240

   16:38:35.207487 IP (tos 0x0, ttl 128, id 11274, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 2920:4380(1460) ack
   1 win 64240

   16:38:35.207538 IP (tos 0x0, ttl 128, id 11275, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 4380:5840(1460) ack
   1 win 64240

   16:38:35.208593 IP (tos 0x0, ttl 128, id 11276, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 1460:2920(1460) ack
   1 win 64240

   16:38:35.209105 IP (tos 0x0, ttl 128, id 11277, offset 0, flags [DF], proto
   TCP (6), length 2960) 10.1.1.145.63094 > 10.1.1.60.80: . 5840:8760(2920) ack
   1 win 64240

   16:38:35.209145 IP (tos 0x0, ttl 128, id 11279, offset 0, flags [DF], proto
   TCP (6), length 2960) 10.1.1.145.63094 > 10.1.1.60.80: . 8760:11680(2920)
   ack 1 win 64240
   eth0 is outgoing to real-servers interface on same server:
   (virtual) foto1 ~ # tcpdump -i eth0 -vv -n port 80 and host 10.1.1.145
   tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 68
   bytes
   16:38:34.896070 IP (tos 0x0, ttl 128, id 11268, offset 0, flags [DF], proto
   TCP    (6),    length   52)   10.1.1.145.63094   >   10.1.1.60.80:   S
   1211165489:1211165489(0) win 8192 <mss 1460,[|tcp]>
   16:38:34.896863 IP (tos 0x0, ttl 128, id 11269, offset 0, flags [DF], proto
   TCP  (6),  length 40) 10.1.1.145.63094 > 10.1.1.60.80: ., cksum 0x6192
   (correct), 1211165490:1211165490(0) ack 2881536955 win 64240
   16:38:35.206692 IP (tos 0x0, ttl 128, id 11273, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 0:1460(1460) ack 1
   win 64240
   16:38:35.207505 IP (tos 0x0, ttl 128, id 11274, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 2920:4380(1460) ack
   1 win 64240
   16:38:35.207542 IP (tos 0x0, ttl 128, id 11275, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 4380:5840(1460) ack
   1 win 64240
   16:38:35.208610 IP (tos 0x0, ttl 128, id 11276, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 1460:2920(1460) ack
   1 win 64240
   16:38:35.520432 IP (tos 0x0, ttl 128, id 11282, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 5840:7300(1460) ack
   1 win 64240
   16:38:35.523322 IP (tos 0x0, ttl 128, id 11283, offset 0, flags [DF], proto
   TCP (6), length 1500) 10.1.1.145.63094 > 10.1.1.60.80: . 11680:13140(1460)
   ack 1 win 64240

    Thanks in advance,
    Deniss
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