我试图通过调整iptables以不跟踪TCP连接的状态来提高服务器的性能.我正在看这个指南：
http://cotdp.com/2011/07/nginix-on-a-256mb-vm-slice-24000-tps/
但是,如果我执行以下任何操作,似乎所有传出连接都被切断：
删除此规则：INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT
添加这些：
iptables -t raw -I OUTPUT -j NOTRACK iptables -t raw -I PREROUTING -j NOTRACK
在进行任何更改之后立即使其“ping google.com”返回关于无法找到“google.com”的错误(即DNS停止解析).
以下是启动时加载的规则,但fail2ban会添加其他规则：
*filter -A INPUT -i lo -j ACCEPT -A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A OUTPUT -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -p tcp --dport ssh -j ACCEPT -A INPUT -p tcp --dport http -j ACCEPT -A INPUT -p tcp --dport https -j ACCEPT -A INPUT -p tcp --dport smtp -j ACCEPT -A INPUT -p tcp --dport ssmtp -j ACCEPT -A INPUT -j REJECT -A FORWARD -j REJECT COMMIT
这是iptables –list的输出：
Chain INPUT (policy ACCEPT) target prot opt source destination fail2ban-ssh tcp -- anywhere anywhere multiport dports ssh fail2ban-ssh-ddos tcp -- anywhere anywhere multiport dports ssh fail2ban-pam-generic tcp -- anywhere anywhere ACCEPT all -- anywhere anywhere REJECT all -- anywhere loopback/8 reject-with icmp-port-unreachable ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT icmp -- anywhere anywhere ACCEPT tcp -- anywhere anywhere tcp dpt:ssh ACCEPT tcp -- anywhere anywhere tcp dpt:www ACCEPT tcp -- anywhere anywhere tcp dpt:https ACCEPT tcp -- anywhere anywhere tcp dpt:smtp ACCEPT tcp -- anywhere anywhere tcp dpt:ssmtp REJECT all -- anywhere anywhere reject-with icmp-port-unreachable Chain FORWARD (policy ACCEPT) target prot opt source destination REJECT all -- anywhere anywhere reject-with icmp-port-unreachable Chain OUTPUT (policy ACCEPT) target prot opt source destination ACCEPT all -- anywhere anywhere Chain fail2ban-pam-generic (1 references) target prot opt source destination RETURN all -- anywhere anywhere Chain fail2ban-ssh (1 references) target prot opt source destination RETURN all -- anywhere anywhere Chain fail2ban-ssh-ddos (1 references) target prot opt source destination RETURN all -- anywhere anywhere
解决方法
您有一个阻止所有传入流量的规则：
-A INPUT -j REJECT
并且您停止连接跟踪,因此接受已建立连接的数据包的规则不再起作用：
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
因此,您的DNS数据包会消失,不会被跟踪,然后被第一条规则拒绝.
您需要启用第二个规则的跟踪才能工作,或者添加规则以允许来自“好”源的传入流量.
