tcp keep alive?

Heiler Bemerguy <heiler.bemerguy@xxxxxxxxxxxxxx> · Mon, 16 Mar 2020 12:13:39 -0300



    Hey Guys,
    I have seen this on my Cyrus server 2.5.10, which is preventing
      new users on IMAP:
    root@mailer:~# netstat -na |grep 177.194.176.48 |wc -l

      27

      root@mailer:~# netstat -na |grep 177.194.176.48

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:56330    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:63680    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:56644    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:55750    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:56624    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:62482    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:63678    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:60218    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:57808    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:49735    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:64322    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:49324    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:57809    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:56639    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:63746    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:62528    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:63675    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:63677    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:61509    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:57196    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:61510    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:57380    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:56814    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:63679    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:49349    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:59459    ESTABELECIDA

      tcp        0      0 10.1.200.226:143       
      177.194.176.48:62539    ESTABELECIDA
    Not even a single byte is sent to this IP (as seen on tcpdump),
      and this Debian's tcp keepalive is set like:
    
      net.ipv4.tcp_keepalive_intvl = 5

        net.ipv4.tcp_keepalive_probes = 3

        net.ipv4.tcp_keepalive_time = 60
    
    And there's an iptables rules like this:
    
      iptables -A INPUT -p tcp --syn --dport 143 -m connlimit
        --connlimit-above 10 --connlimit-mask 32 -j REJECT

        iptables -A INPUT -p tcp --syn --dport 143 -j ACCEPT

      
    Even though this user is multiple connected like that for
      HOURS.......
    -- 
Best Regards,

Heiler Bemerguy - CINBESA
Analista de Redes, Wi-Fi,
Virtualização e Serviços Internet
(55) 91 98151-4894
  

----
Cyrus Home Page: http://www.cyrusimap.org/
List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
To Unsubscribe:
https://lists.andrew.cmu.edu/mailman/listinfo/info-cyrus