Network issues on lenny

[Marek Podmaka <marki@marki-online.net>]

Hello all,

During the weekend I re-installed our mail server (sarge 32bit) into
lenny 64bit with debian kernel 2.6.26-1-amd64. Everything works, but
customers are reporting weird connection issues to postfix. Sometimes
it works and sometimes not. Few of them are connected using the same
DSL provider, but not all.

Mar 24 10:59:19 kenny postfix/smtpd[12702]: connect from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:19 kenny postfix/smtpd[12702]: lost connection after CONNECT from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:19 kenny postfix/smtpd[12702]: disconnect from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:19 kenny postfix/smtpd[19350]: connect from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:19 kenny postfix/smtpd[19350]: lost connection after CONNECT from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:19 kenny postfix/smtpd[19350]: disconnect from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:33 kenny postfix/smtpd[12702]: connect from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:33 kenny postfix/smtpd[12702]: lost connection after CONNECT from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 10:59:33 kenny postfix/smtpd[12702]: disconnect from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 11:00:19 kenny postfix/smtpd[19350]: connect from adsl-dyn113.91-127-26.t-com.sk[91.127.26.113]
Mar 24 11:00:19 kenny postfix/smtpd[19350]: AE9D9200169: client=adsl-dyn113.91-127-26.t-com.sk[91.127.26.113], sasl_method=LOGIN, sasl_username=xxx

Do you have idea what could be causing it? Looks like it doesn't work
for few hours, then works for few hours (means every connection from
that ip is ok) and then again stops working...

Some new tcp parameter that could be incompatible with routers along
the path?

Here are current TCP settings:
kenny:/proc/sys/net/ipv4:# for i in tcp*; do echo -n "$i: "; cat $i; done
tcp_abc: 0
tcp_abort_on_overflow: 0
tcp_adv_win_scale: 2
tcp_allowed_congestion_control: cubic reno
tcp_app_win: 31
tcp_available_congestion_control: cubic reno
tcp_base_mss: 512
tcp_congestion_control: cubic
tcp_dma_copybreak: 4096
tcp_dsack: 1
tcp_ecn: 0
tcp_fack: 1
tcp_fin_timeout: 60
tcp_frto: 0
tcp_frto_response: 0
tcp_keepalive_intvl: 75
tcp_keepalive_probes: 9
tcp_keepalive_time: 7200
tcp_low_latency: 0
tcp_max_orphans: 65536
tcp_max_ssthresh: 0
tcp_max_syn_backlog: 1024
tcp_max_tw_buckets: 180000
tcp_mem: 380544 507392  761088
tcp_moderate_rcvbuf: 1
tcp_mtu_probing: 0
tcp_no_metrics_save: 0
tcp_orphan_retries: 0
tcp_reordering: 3
tcp_retrans_collapse: 1
tcp_retries1: 3
tcp_retries2: 15
tcp_rfc1337: 0
tcp_rmem: 4096  87380   4194304
tcp_sack: 1
tcp_slow_start_after_idle: 1
tcp_stdurg: 0
tcp_synack_retries: 5
tcp_syncookies: 0
tcp_syn_retries: 5
tcp_timestamps: 1
tcp_tso_win_divisor: 3
tcp_tw_recycle: 0
tcp_tw_reuse: 0
tcp_window_scaling: 1
tcp_wmem: 4096  16384   4194304
tcp_workaround_signed_windows: 0


   Thanks!
  

-- 
  bYE, Marki