????TCP???1974?????????????????30??????????????????????????Э?飬??TCPЭ??????????Щ????
????SYN??????????TCPЭ????????????????????????????????
????SYN???????

????TCP??????????????????????????SYN??????????????????????SYN?????????α???IP?????
???????????????SYN?????????????????backlog???У??????IP????SYN-ACK????????????ACK????????????????????????????
?????????IP?????α????????????IP?????????????????ACK????????????????????backlog???б????????????SYN???????????????????????????????
????SYN????????
???????SYN??????????????????????????????
???????1??????SYN-ACK?????????????????????5?Σ???
????sysctl -w net.ipv4.tcp_synack_retries=3
????sysctl -w net.ipv4.tcp_syn_retries=3
???????2?????SYN Cookie??????
????sysctl -w net.ipv4.tcp_syncookies=1
???????3??????backlog???У??????1024????
????sysctl -w net.ipv4.tcp_max_syn_backlog=2048
???????4??????SYN????????
????iptables -A INPUT -p tcp --syn -m limit --limit 1/s -j ACCEPT --limit 1/s
????SYN???????
?????????????????hping?????????SYN???????μ???Linux???????繤???hping?????????衷??
???????????synkill????????????SYN??????