Trouble sending large emails

[bosje]

Hi,
I have a problem sending emails with size larger than approx 4K. I have no idea if the problem is my installation, the firewall or my provider and I have no idea where to start finding out. Sending smaller mails works OK. I hope someone can help me. My system is as follows:

Client: Gentoo 1.4, qmail, kmail client
Firewall: Suse 7.3, iptables

When i do a tcpdump at the client I see

21:43:34.453455 [client].33075 > [smtp-serv].smtp: . 8788:10236(1448) ack 396 win 6432 <nop,nop,timestamp 676535 40475855> (DF)
21:43:34.982634 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 676588 40475855> (DF)
21:43:36.042637 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 676694 40475855> (DF)
21:43:38.162617 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 676906 40475855> (DF)
21:43:42.402592 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 677330 40475855> (DF)
21:43:50.882547 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 678178 40475855> (DF)
21:44:07.842457 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 679874 40475855> (DF)
21:44:41.762281 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 683266 40475855> (DF)
21:44:46.762237 arp who-has [firewall] tell [client]
21:44:46.762391 arp reply [firewall] is-at 0:2:44:5f:d5:21
21:45:49.601917 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 690050 40475855> (DF)
21:47:49.601280 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 702050 40475855> (DF)
21:47:54.601238 arp who-has [firewall] tell [client]
21:47:54.601390 arp reply [firewall] is-at 0:2:44:5f:d5:21
21:49:49.600642 [client].33075 > [smtp-serv].smtp: . 7340:8788(1448) ack 396 win 6432 <nop,nop,timestamp 714050 40475855> (DF)
21:49:54.600600 arp who-has [firewall] tell [client]
21:49:54.600753 arp reply [firewall] is-at 0:2:44:5f:d5:21

etc.

This goes on for several minute after which I get a 'broken connection' message from kmail.

Please help!
Mike

[lim]

Hi,

I have a similar problem. TCP connections seem to hang arbitrarily for
30 seconds to several minutes. Patient programs like telnet survive this.
Other programs like ftp (when emerging) tend to block or timeout.
Luckily ftp can recover and continue broken downloads, so eventually
emerging of large packages works.

The problem occurs on all kinds of network cards, tried 3 different.
The problem is not that bad that it is totally unworkable. WWW browsing
works well for instance.
My firewall is a good old RH 6.2; the problematic machine started with
the gentoo kernel 2.4.19

To start debugging, I tried the vanilla kernel 2.4.20 first. No luck.
Then I tried to boot a knoppix distribution, which seemed to work fine. So
I stole the .config from the knoppix distribution, just changed the
processor type to athlon, added Reiserfs support in the kernel as my root
fs is Reiserfs, and added devfs support because booting a kernel without
it makes gentoo complain.
Still no luck, so does one of these things make the difference ?

I also took tcpdump output, remarkably my problems also start after the
machine apparently looses its ARP entry for my firewall (see extract
below). After that you also see RST packets sent by the gentoo machine.
These don't actually reset the TCP connection, they probably dont fall
in the window of the peer (A RST packet is normally a response on a
packet coming in on the machine and for which the machine does not
have an established connection).

Any clues, anyone ... ?

22:43:41.930265 192.168.2.254.23 > 192.168.2.5.32781: P 4620:5745(1125) ack 33 win 32120 <nop,nop,timestamp 17986955 193863> (DF)
22:43:41.931490 192.168.2.5.32781 > 192.168.2.254.23: R 3025667827:3025667827(0) ack 4621 win 32120 <eol>
22:43:43.029570 arp who-has 192.168.2.5 tell 192.168.2.254
22:43:43.029982 arp reply 192.168.2.5 is-at 0:30:65:2e:da:fe
22:43:45.770163 192.168.2.5.32781 > 192.168.2.254.23: P 32:33(1) ack 4620 win 33792 <nop,nop,timestamp 194263 17983998> (DF) [tos 0x10]
22:43:45.770490 192.168.2.254.23 > 192.168.2.5.32781: . ack 33 win 32120 <nop,nop,timestamp 17987339 194263> (DF)
22:43:45.770897 192.168.2.5.32781 > 192.168.2.254.23: R 3025667827:3025667827(0) ack 7794 win 32120 <eol>
22:43:46.089249 192.168.2.254.23 > 192.168.2.5.32781: P 4620:5745(1125) ack 33 win 32120 <nop,nop,timestamp 17987371 194263> (DF)
22:43:46.090065 192.168.2.5.32781 > 192.168.2.254.23: R 3025667827:3025667827(0) ack 4621 win 32120 <eol>
22:43:53.770164 192.168.2.5.32781 > 192.168.2.254.23: P 32:33(1) ack 4620 win 33792 <nop,nop,timestamp 195063 17983998> (DF) [tos 0x10]
22:43:53.770516 192.168.2.254.23 > 192.168.2.5.32781: . ack 33 win 32120 <nop,nop,timestamp 17988139 195063> (DF)
22:43:53.770923 192.168.2.5.32781 > 192.168.2.254.23: R 3025667827:3025667827(0) ack 7794 win 32120 <eol>
22:43:54.406661 192.168.2.254.23 > 192.168.2.5.32781: P 4620:5745(1125) ack 33 win 32120 <nop,nop,timestamp 17988203 195063> (DF)
22:43:54.408031 192.168.2.5.32781 > 192.168.2.254.23: R 3025667827:3025667827(0) ack 4621 win 32120 <eol>
22:44:09.770166 192.168.2.5.32781 > 192.168.2.254.23: P 32:33(1) ack 4620 win 33792 <nop,nop,timestamp 196663 17983998> (DF) [tos 0x10]
22:44:09.770567 192.168.2.254.23 > 192.168.2.5.32781: . ack 33 win 32120 <nop,nop,timestamp 17989739 196663> (DF)
22:44:09.770974 192.168.2.5.32781 > 192.168.2.254.23: R 3025667827:3025667827(0) ack 7794 win 32120 <eol>