2012-05-29

hadoop.nchc.org.tw

• 錯誤訊息：nf_conntrack: table full, dropping packet.

  ~$ dmesg | grep 
  [1146203.787306] nf_conntrack: table full, dropping packet.
  [1146203.787880] nf_conntrack: table full, dropping packet.
  [1146203.790825] nf_conntrack: table full, dropping packet.
  [1146203.791307] nf_conntrack: table full, dropping packet.
  [1146203.791503] nf_conntrack: table full, dropping packet.
  [1146203.791818] nf_conntrack: table full, dropping packet.
  [1146203.791987] nf_conntrack: table full, dropping packet.
  [1146208.785365] nf_conntrack: table full, dropping packet.
  [1146208.785635] nf_conntrack: table full, dropping packet.
  [1146208.786510] nf_conntrack: table full, dropping packet.
  

• [參考] ​Resolving “nf_conntrack: table full, dropping packet.” flood message in dmesg Linux kernel log
• [參考] ​what is the meaning nf_conntrack: table full, dropping packet.
• [原因] 阻斷攻擊（DDoS）
• [解法] 修改 /etc/sysctl.conf 增加 ip_conntrack_max 、降低 ip_conntrack_generic_timeout

  net.ipv4.netfilter.ip_conntrack_max=16384
  net.ipv4.conf.default.arp_ignore=1
  net.ipv4.conf.all.arp_ignore=1
  net.ipv4.ip_forward=1
  net.ipv4.icmp_echo_ignore_broadcasts=1
  net.ipv4.icmp_ignore_bogus_error_responses=1
  net.ipv4.tcp_ecn=1
  net.ipv4.tcp_fin_timeout=30
  net.ipv4.tcp_keepalive_time=120
  net.ipv4.tcp_syncookies=1
  net.ipv4.tcp_timestamps=0
  net.ipv4.netfilter.ip_conntrack_tcp_timeout_established=300
  net.ipv4.netfilter.ip_conntrack_udp_timeout=60
  net.ipv4.netfilter.ip_conntrack_udp_timeout_stream=180
  net.ipv4.netfilter.ip_conntrack_generic_timeout = 120
  net.ipv4.netfilter.ip_conntrack_tcp_timeout_established = 54000