trouble about IP Fragmentation by using the Linux Virtual Server

[<frederic.buche@xxxxxxxxxx>]

Hello,

We have some trouble about IP Fragmentation by using the Linux Virtual Server and ISDN connection

It works as follow :
User   -->    LVS    --> WinNT Servers

If the user who send the SMTP message use an ISDN (RNIS) connection, there is some fragmentation on the ip datagramm.
(see the logs bellow)
The fragmentation is absolutly normal, but what happens is that the connection is bloked, as we can see in the Tcpdump's logs.

Our configuration is :  a kernel 2.4.18 and the ipvs patch 1.0.6
(we tried also the other patches 1.00 ans 1.0.1)

But this kind of ISDN connection works properly with an old version of the LVS (ipvs patch 0.9.15) with a Kernel 2.2.16.

We tried to know if our problem was coming from the Linux ip layer or from the IPVS.
So we set up an address tranlation to another server, in order that each ip datagramm should be relayed.
This test was working properly, that's means the Linux ip layer is correct.

It seems that the bug comes from the ipvs.

Has someone an idea about that ?
Is there any solution to thus problem

Regards

Frédéric BUCHE
mailto : frederic.buche@xxxxxxxxxx

LOGS :

13:56:23.984801 195.101.125.28.10708 > 195.6.241.14.smtp: S 70109:70109(0) win 8192 <mss 1460> (DF) [tos 0x10]
13:56:23.984908 195.101.125.28.10708 > 195.6.241.14.smtp: S 70109:70109(0) win 8192 <mss 1460> (DF) [tos 0x10]
13:56:23.985314 195.101.125.28.10708 > 195.6.241.14.smtp: . ack 134786757 win 0
13:56:23.985349 195.101.125.28.10708 > 195.6.241.14.smtp: . ack 1 win 0
13:56:23.986075 195.101.125.28.10708 > 195.6.241.14.smtp: . ack 1 win 0 (DF)
13:56:23.986097 195.101.125.28.10708 > 195.6.241.14.smtp: . ack 1 win 0 (DF)
13:56:24.087866 195.101.125.28.10708 > 195.6.241.14.smtp: . ack 1 win 8760 (DF) [tos 0x10]
13:56:24.087920 195.101.125.28.10708 > 195.6.241.14.smtp: . ack 1 win 8760 (DF) [tos 0x10]
13:56:24.213102 195.101.125.28.10708 > 195.6.241.14.smtp: P 0:16(16) ack 114 win 8647 (DF) [tos 0x10]
13:56:24.213118 195.101.125.28.10708 > 195.6.241.14.smtp: P 0:16(16) ack 114 win 8647 (DF) [tos 0x10]
13:56:24.336694 195.101.125.28.10708 > 195.6.241.14.smtp: P 16:45(29) ack 157 win 8604 (DF) [tos 0x10]
13:56:24.336714 195.101.125.28.10708 > 195.6.241.14.smtp: P 16:45(29) ack 157 win 8604 (DF) [tos 0x10]
13:56:24.444246 195.101.125.28.10708 > 195.6.241.14.smtp: P 45:82(37) ack 190 win 8571 (DF) [tos 0x10]
13:56:24.444271 195.101.125.28.10708 > 195.6.241.14.smtp: P 45:82(37) ack 190 win 8571 (DF) [tos 0x10]
13:56:24.560986 195.101.125.28.10708 > 195.6.241.14.smtp: P 82:88(6) ack 234 win 8527 (DF) [tos 0x10]
13:56:24.561007 195.101.125.28.10708 > 195.6.241.14.smtp: P 82:88(6) ack 234 win 8527 (DF) [tos 0x10]
13:56:25.092387 195.101.125.28.10708 > 195.6.241.14.smtp: . 88:1516(1428) ack 295 win 8466 (frag 45105:1448@0+) [tos 0x10]
13:56:25.092392 195.101.125.28 > 195.6.241.14: (frag 45105:32@1448) [tos 0x10]
13:56:25.092479 195.101.125.28.10708 > 195.6.241.14.smtp: . 88:1548(1460) ack 295 win 8466 [tos 0x10]
13:56:25.094999 195.101.125.28.10708 > 195.6.241.14.smtp: P 1548:1893(345) ack 295 win 8466 (DF) [tos 0x10]
13:56:25.095019 195.101.125.28.10708 > 195.6.241.14.smtp: P 1548:1893(345) ack 295 win 8466 (DF) [tos 0x10]
13:56:25.189054 195.101.125.28.10708 > 195.6.241.14.smtp: P 1893:1898(5) ack 295 win 8466 (DF) [tos 0x10]
13:56:25.189070 195.101.125.28.10708 > 195.6.241.14.smtp: P 1893:1898(5) ack 295 win 8466 (DF) [tos 0x10]
13:56:25.708165 195.101.125.28.10708 > 195.6.241.14.smtp: . 88:1516(1428) ack 295 win 8466 (frag 45873:1448@0+) [tos 0x10]
13:56:25.708167 195.101.125.28 > 195.6.241.14: (frag 45873:32@1448) [tos 0x10]
13:56:25.708207 195.101.125.28.10708 > 195.6.241.14.smtp: . 88:1548(1460) ack 295 win 8466 [tos 0x10]
13:56:26.925692 195.101.125.28.10708 > 195.6.241.14.smtp: . 88:1516(1428) ack 295 win 8466 (frag 46385:1448@0+) [tos 0x10]