如何减lessTIME_WAIT进程的数量?

$ netstat -an | awk '/tcp/ {print $6}' | sort | uniq -c 92 ESTABLISHED 1 FIN_WAIT2 13 LISTEN 7979 TIME_WAIT 

 $ grep processor /proc/cpuinfo | wc -l 4 

 $ grep -r keep.*alive /etc/ /etc/ufw/sysctl.conf:#net/ipv4/tcp_keepalive_intvl=1800 /etc/nginx/nginx.conf: keepalive_timeout 5 5; 

 $ free -m total used free shared buffers cached Mem: 14980 1402 13577 0 113 831 -/+ buffers/cache: 458 14521 Swap: 0 0 0 

  $ uptime 02:17:14 up 18:20, 1 user, load average: 2.77, 2.39, 2.21 

 $ dstat You did not select any stats, using -cdngy by default. ----total-cpu-usage---- -dsk/total- -net/total- ---paging-- ---system-- usr sys idl wai hiq siq| read writ| recv send| in out | int csw 46 2 51 0 0 1|4432B 10k| 0 0 | 0 0 |4346 1870 51 3 46 0 0 1| 0 56k|2679k 191k| 0 0 |5130 2318 40 3 57 0 0 1| 0 0 |1566k 211k| 0 0 |4825 2141 46 2 52 0 0 0| 0 0 |1311k 136k| 0 0 |4606 1997 27 2 71 0 0 1| 0 0 | 234k 144k| 0 0 |3278 1693 23 2 76 0 0 0| 0 152k| 286k 123k| 0 0 |3094 1683 23 2 74 1 0 0| 0 28k| 146k 131k| 0 0 |3103 1576 30 2 67 0 0 1| 0 0 | 668k 177k| 0 0 |4023 2020 31 2 67 0 0 0| 0 0 | 326k 197k| 0 0 |4330 2273 23 2 75 0 0 0| 0 0 | 339k 121k| 0 0 |3020 1428 30 2 67 0 0 0| 0 0 |1930k 180k| 0 0 |4487 1947 38 3 59 0 0 1| 0 12k| 340k 155k| 0 0 |4403 1994 29 2 68 0 0 1| 0 0 | 187k 117k| 0 0 |3449 1729 35 4 59 2 0 1| 0 0 | 478k 314k| 0 0 |4415 2338 49 4 46 0 0 1| 0 0 |2263k 210k| 0 0 |5153 2289 49 2 49 0 0 1| 0 60k|2921k 118k| 0 0 |5063 1532 52 2 46 0 0 0| 0 24k|2823k 161k| 0 0 |4842 1740 72 2 26 0 0 1| 0 0 |2361k 141k| 0 0 |4715 1600 62 3 34 0 0 1| 0 0 |3414k 147k| 0 0 |5487 1863 48 2 49 0 0 1| 0 0 |1501k 117k| 0 0 |4211 1722 49 4 46 0 0 1| 0 0 |4675k 207k| 0 0 |5660 2286 46 2 51 0 0 0| 0 0 | 182k 169k| 0 0 |4178 2373 43 1 55 0 0 0| 0 12k| 172k 168k| 0 0 |3407 1843 29 2 69 0 0 0| 0 0 | 376k 175k| 0 0 |4013 2216 29 2 68 0 0 0| 0 0 | 613k 238k| 0 0 |4885 2628 25 2 72 0 0 1| 0 0 | 272k 215k| 0 0 |5105 3126 33 3 63 0 0 1| 0 0 |3692k 228k| 0 0 |5978 2397 ^C 

 $ cat /etc/sysctl.conf # Avoid a smurf attack net.ipv4.icmp_echo_ignore_broadcasts = 1 # Turn on protection for bad icmp error messages net.ipv4.icmp_ignore_bogus_error_responses = 1 # Turn on syncookies for SYN flood attack protection net.ipv4.tcp_syncookies = 1 # Turn on and log spoofed, source routed, and redirect packets net.ipv4.conf.all.log_martians = 1 net.ipv4.conf.default.log_martians = 1 # No source routed packets here net.ipv4.conf.all.accept_source_route = 0 net.ipv4.conf.default.accept_source_route = 0 # Turn on reverse path filtering net.ipv4.conf.all.rp_filter = 1 net.ipv4.conf.default.rp_filter = 1 # Make sure no one can alter the routing tables net.ipv4.conf.all.accept_redirects = 0 net.ipv4.conf.default.accept_redirects = 0 net.ipv4.conf.all.secure_redirects = 0 net.ipv4.conf.default.secure_redirects = 0 # Don't act as a router net.ipv4.ip_forward = 0 net.ipv4.conf.all.send_redirects = 0 net.ipv4.conf.default.send_redirects = 0 # Turn on execshild kernel.exec-shield = 1 kernel.randomize_va_space = 1 # Tuen IPv6 net.ipv6.conf.default.router_solicitations = 0 net.ipv6.conf.default.accept_ra_rtr_pref = 0 net.ipv6.conf.default.accept_ra_pinfo = 0 net.ipv6.conf.default.accept_ra_defrtr = 0 net.ipv6.conf.default.autoconf = 0 net.ipv6.conf.default.dad_transmits = 0 net.ipv6.conf.default.max_addresses = 1 # Optimization for port usefor LBs # Increase system file descriptor limit fs.file-max = 65535 # Allow for more PIDs (to reduce rollover problems); may break some programs 32768 kernel.pid_max = 65536 # Increase system IP port limits net.ipv4.ip_local_port_range = 2000 65000 # Increase TCP max buffer size setable using setsockopt() net.ipv4.tcp_rmem = 4096 87380 8388608 net.ipv4.tcp_wmem = 4096 87380 8388608 # Increase Linux auto tuning TCP buffer limits # min, default, and max number of bytes to use # set max to at least 4MB, or higher if you use very high BDP paths # Tcp Windows etc net.core.rmem_max = 8388608 net.core.wmem_max = 8388608 net.core.netdev_max_backlog = 5000 net.ipv4.tcp_window_scaling = 1 

 $ 2>/dev/null sysctl -a | grep \ 'tcp_syncookies\|tcp_max_syn_backlog\|tcp_synack_retries' net.ipv4.tcp_synack_retries = 5 net.ipv4.tcp_syncookies = 1 net.ipv4.tcp_max_syn_backlog = 2048 

问题:什么可能导致大量的TIME_WAIT?

我有解决scheme:

 # This setting allows sockets reusing. $ echo 'net.ipv4.tcp_tw_recycle = 1' >> /etc/sysctl.conf $ sysctl -p /etc/sysctl.conf 

TIME_WAIT是未完成的TCP会话请求。 这可能是由SYN Flood拒绝服务攻击造成的 。

这种攻击是无法完全避免的,但是在文章中强化TCP / IP协议栈以防止SYN Floods有一些有用的技巧,可以有效地减轻其影响。