{"id":1162,"date":"2014-01-20T10:50:46","date_gmt":"2014-01-20T02:50:46","guid":{"rendered":"http:\/\/nick.txtcc.com\/?p=1162"},"modified":"2014-01-20T11:23:51","modified_gmt":"2014-01-20T03:23:51","slug":"tcp_tw_recycle%e5%92%8ctcp_timestamps%e5%af%bc%e8%87%b4connect%e5%a4%b1%e8%b4%a5%e9%97%ae%e9%a2%98","status":"publish","type":"post","link":"http:\/\/nick.txtcc.com\/index.php\/linux\/1162","title":{"rendered":"tcp_tw_recycle\u548ctcp_timestamps\u5bfc\u81f4connect\u5931\u8d25\u95ee\u9898"},"content":{"rendered":"<p>\u8fd1\u6765\u7ebf\u4e0a\u9646\u7eed\u51fa\u73b0\u4e86\u4e00\u4e9bconnect\u5931\u8d25\u7684\u95ee\u9898\uff0c\u7ecf\u8fc7\u5206\u6790\u8bd5\u9a8c\uff0c\u6700\u7ec8\u786e\u8ba4\u548cproc\u53c2\u6570tcp_tw_recycle\/tcp_timestamps\u76f8\u5173\uff1b<\/p>\n<ol>\n<li>\u73b0\u8c61<\/li>\n<\/ol>\n<p>\u7b2c\u4e00\u4e2a\u73b0\u8c61\uff1a\u6a21\u5757A\u901a\u8fc7NAT\u7f51\u5173\u8bbf\u95ee\u670d\u52a1S\u6210\u529f\uff0c\u800c\u6a21\u5757B\u901a\u8fc7NAT\u7f51\u5173\u8bbf\u95ee\u670d\u52a1S\u7ecf\u5e38\u6027\u51fa\u73b0connect\u5931\u8d25\uff0c\u6293\u5305\u53d1\u73b0\uff1a\u670d\u52a1S\u7aef\u5df2\u7ecf\u6536\u5230\u4e86syn\u5305\uff0c\u4f46\u6ca1\u6709\u56de\u590dsynack\uff1b\u53e6\u5916\uff0c\u6a21\u5757A\u5173\u95ed\u4e86tcp timestamp\uff0c\u800c\u6a21\u5757B\u5f00\u542f\u4e86tcp timestamp\uff1b<\/p>\n<p>\u7b2c\u4e8c\u4e2a\u73b0\u8c61\uff1a\u4e0d\u540c\u4e3b\u673a\u4e0a\u7684\u6a21\u5757C\uff08\u5f00\u542ftimestamp\uff09\uff0c\u901a\u8fc7NAT\u7f51\u5173\uff081\u4e2a\u51fa\u53e3ip\uff09\u8bbf\u95ee\u540c\u4e00\u670d\u52a1S\uff0c\u4e3b\u673aC1 connect\u6210\u529f\uff0c\u800c\u4e3b\u673aC2 connect\u5931\u8d25\uff1b<\/p>\n<p>&nbsp;<\/p>\n<ol start=\"2\">\n<li>\u5206\u6790<\/li>\n<\/ol>\n<p>\u6839\u636e\u73b0\u8c61\u4e0a\u8ff0\u95ee\u9898\u660e\u663e\u548ctcp timestmap\u6709\u5173\uff1b\u67e5\u770blinux 2.6.32\u5185\u6838\u6e90\u7801\uff0c\u53d1\u73b0tcp_tw_recycle\/tcp_timestamps\u90fd\u5f00\u542f\u7684\u6761\u4ef6\u4e0b\uff0c60s\u5185\u540c\u4e00\u6e90ip\u4e3b\u673a\u7684socket connect\u8bf7\u6c42\u4e2d\u7684timestamp\u5fc5\u987b\u662f\u9012\u589e\u7684\u3002<\/p>\n<p>\u6e90\u7801\u51fd\u6570\uff1atcp_v4_conn_request(),\u8be5\u51fd\u6570\u662ftcp\u5c42\u4e09\u6b21\u63e1\u624bsyn\u5305\u7684\u5904\u7406\u51fd\u6570\uff08\u670d\u52a1\u7aef\uff09\uff1b<\/p>\n<p>\u6e90\u7801\u7247\u6bb5\uff1a<\/p>\n<p>if (tmp_opt.saw_tstamp &#038;&#038;<\/p>\n<p>tcp_death_row.sysctl_tw_recycle &#038;&#038;<\/p>\n<p>(dst = inet_csk_route_req(sk, req)) != NULL &#038;&#038;<\/p>\n<p>(peer = rt_get_peer((struct rtable *)dst)) != NULL &#038;&#038;<\/p>\n<p>peer->v4daddr == saddr) {<\/p>\n<p>if (get_seconds() < peer->tcp_ts_stamp + TCP_PAWS_MSL &#038;&#038;<\/p>\n<p>(s32)(peer->tcp_ts &#8211; req->ts_recent) ><\/p>\n<p>TCP_PAWS_WINDOW) {<\/p>\n<p>NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSPASSIVEREJECTED);<\/p>\n<p>goto drop_and_release;<\/p>\n<p>}<\/p>\n<p>}<\/p>\n<p>tmp_opt.saw_tstamp\uff1a\u8be5socket\u652f\u6301tcp_timestamp<\/p>\n<p>sysctl_tw_recycle\uff1a\u672c\u673a\u7cfb\u7edf\u5f00\u542ftcp_tw_recycle\u9009\u9879<\/p>\n<p>TCP_PAWS_MSL\uff1a60s\uff0c\u8be5\u6761\u4ef6\u5224\u65ad\u8868\u793a\u8be5\u6e90ip\u7684\u4e0a\u6b21tcp\u901a\u8baf\u53d1\u751f\u572860s\u5185<\/p>\n<p>TCP_PAWS_WINDOW\uff1a1\uff0c\u8be5\u6761\u4ef6\u5224\u65ad\u8868\u793a\u8be5\u6e90ip\u7684\u4e0a\u6b21tcp\u901a\u8baf\u7684timestamp \u5927\u4e8e \u672c\u6b21tcp<\/p>\n<p>&nbsp;<\/p>\n<p>\u5206\u6790\uff1a\u4e3b\u673aclient1\u548cclient2\u901a\u8fc7NAT\u7f51\u5173\uff081\u4e2aip\u5730\u5740\uff09\u8bbf\u95eeserverN\uff0c\u7531\u4e8etimestamp\u65f6\u95f4\u4e3a\u7cfb\u7edf\u542f\u52a8\u5230\u5f53\u524d\u7684\u65f6\u95f4\uff0c\u56e0\u6b64\uff0cclient1\u548cclient2\u7684timestamp\u4e0d\u76f8\u540c\uff1b\u6839\u636e\u4e0a\u8ff0syn\u5305\u5904\u7406\u6e90\u7801\uff0c\u5728tcp_tw_recycle\u548ctcp_timestamps\u540c\u65f6\u5f00\u542f\u7684\u6761\u4ef6\u4e0b\uff0ctimestamp\u5927\u7684\u4e3b\u673a\u8bbf\u95eeserverN\u6210\u529f\uff0c\u800ctimestmap\u5c0f\u7684\u4e3b\u673a\u8bbf\u95ee\u5931\u8d25\uff1b<\/p>\n<p>&nbsp;<\/p>\n<p>\u53c2\u6570\uff1a\/proc\/sys\/net\/ipv4\/tcp_timestamps &#8211; \u63a7\u5236timestamp\u9009\u9879\u5f00\u542f\/\u5173\u95ed<\/p>\n<p>\/proc\/sys\/net\/ipv4\/tcp_tw_recycle &#8211; \u51cf\u5c11timewait socket\u91ca\u653e\u7684\u8d85\u65f6\u65f6\u95f4<\/p>\n<p>&nbsp;<\/p>\n<ol start=\"3\">\n<li>\u89e3\u51b3\u65b9\u6cd5<\/li>\n<\/ol>\n<p>echo 0 > \/proc\/sys\/net\/ipv4\/tcp_tw_recycle;<\/p>\n<p>tcp_tw_recycle\u9ed8\u8ba4\u662f\u5173\u95ed\u7684\uff0c\u6709\u4e0d\u5c11\u670d\u52a1\u5668\uff0c\u4e3a\u4e86\u63d0\u9ad8\u6027\u80fd\uff0c\u5f00\u542f\u4e86\u8be5\u9009\u9879\uff1b<\/p>\n<p>\u4e3a\u4e86\u89e3\u51b3\u4e0a\u8ff0\u95ee\u9898\uff0c\u4e2a\u4eba\u5efa\u8bae\u5173\u95edtcp_tw_recycle\u9009\u9879\uff0c\u800c\u4e0d\u662ftimestamp\uff1b\u56e0\u4e3a \u5728tcp timestamp\u5173\u95ed\u7684\u6761\u4ef6\u4e0b\uff0c\u5f00\u542ftcp_tw_recycle\u662f\u4e0d\u8d77\u4f5c\u7528\u7684\uff1b\u800ctcp timestamp\u53ef\u4ee5\u72ec\u7acb\u5f00\u542f\u5e76\u8d77\u4f5c\u7528\u3002<\/p>\n<p>\u6e90\u7801\u51fd\u6570\uff1a\u00a0 tcp_time_wait()<\/p>\n<p>\u6e90\u7801\u7247\u6bb5\uff1a<\/p>\n<p>if (tcp_death_row.sysctl_tw_recycle &#038;&#038; tp->rx_opt.ts_recent_stamp)<\/p>\n<p>recycle_ok = icsk->icsk_af_ops->remember_stamp(sk);<\/p>\n<p>&#8230;&#8230;<\/p>\n<p>if (timeo < rto)<\/p>\n<p>timeo = rto;<\/p>\n<p>&nbsp;<\/p>\n<p>if (recycle_ok) {<\/p>\n<p>tw->tw_timeout = rto;<\/p>\n<p>} else {<\/p>\n<p>tw->tw_timeout = TCP_TIMEWAIT_LEN;<\/p>\n<p>if (state == TCP_TIME_WAIT)<\/p>\n<p>timeo = TCP_TIMEWAIT_LEN;<\/p>\n<p>}<\/p>\n<p>&nbsp;<\/p>\n<p>inet_twsk_schedule(tw, &#038;tcp_death_row, timeo,<\/p>\n<p>TCP_TIMEWAIT_LEN);<\/p>\n<p>&nbsp;<\/p>\n<p>timestamp\u548ctw_recycle\u540c\u65f6\u5f00\u542f\u7684\u6761\u4ef6\u4e0b\uff0ctimewait\u72b6\u6001socket\u91ca\u653e\u7684\u8d85\u65f6\u65f6\u95f4\u548crto\u76f8\u5173\uff1b\u5426\u5219\uff0c\u8d85\u65f6\u65f6\u95f4\u4e3aTCP_TIMEWAIT_LEN\uff0c\u537360s\uff1b<\/p>\n<p>&nbsp;<\/p>\n<p>\u5185\u6838\u8bf4\u660e\u6587\u6863 \u5bf9\u8be5\u53c2\u6570\u7684\u4ecb\u7ecd\u5982\u4e0b\uff1a<\/p>\n<p>tcp_tw_recycle &#8211; BOOLEAN<\/p>\n<p>Enable fast recycling TIME-WAIT sockets. Default value is 0.<\/p>\n<p>It should not be changed without advice\/request of technical<\/p>\n<p>experts.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<table cellspacing=\"0\" cellpadding=\"0\">\n<tbody>\n<tr>\n<td id=\"postmessage_395\"><strong>\u7c7b\u4f3c\u7684\u6545\u969c\u573a\u666f\uff1a<\/strong>\n\u51e0\u53f0\u901a\u8fc7NAT\u8bbf\u95ee\u4e00\u53f0\u670d\u52a1\u5668\uff0c\u670d\u52a1\u5668\u4e0a\u5f00\u542f\u4e86tcp_tw_recycle\u7528\u4e8eTIME_WAIT\u7684\u5feb\u901f\u56de\u6536<strong>\u6545\u969c\u73b0\u8c61\u548c\u5206\u6790\u6b65\u9aa4\uff1a<\/strong>\n1) \u901a\u8fc7NAT\u51fa\u53e3\u7684\u5ba2\u6237\u7aef\u7ecf\u5e38\u8bf7\u6c42Web\u670d\u52a1\u5668\u65e0\u54cd\u5e94\uff0ctelnet\u670d\u52a1\u5668\u7aef\u53e3\u4e0d\u901a\uff0c\u4f46\u662f\u53ef\u4ee5ping\u901a\u3002\u540c\u4e00\u673a\u623f\uff0c\u6709\u72ec\u7acbIP\u5730\u5740\u7684\u670d\u52a1\u5668\u4e0d\u5b58\u5728\u8fd9\u6837\u7684\u95ee\u9898\uff1b\n2) \u5728\u670d\u52a1\u5668\u6293\u5305\uff0c\u53d1\u73b0\u670d\u52a1\u7aef\u53ef\u4ee5\u6536\u5230\u5ba2\u6237\u7aef\u7684SYN\u8bf7\u6c42\uff0c\u4f46\u662f\u6ca1\u6709\u56de\u5e94SYN,ACK\uff0c\u4e5f\u5c31\u662f\u8bf4\u5185\u6838\u76f4\u63a5\u5c06\u5305\u4e22\u5f03\u4e86\u3002\n\n<strong>\u89e3\u51b3\u65b9\u6cd5\uff1a<\/strong>\n1) \u5173\u95ed\u670d\u52a1\u5176\u7aef\u7684tcp_timestamps\uff0c\u6545\u969c\u89e3\u51b3\uff0c\u4f46\u662f\u8fd9\u4e48\u505a\u5b58\u5728\u5b89\u5168\u548c\u6027\u80fd\u9690\u60a3\uff1b\n2) \u5173\u95edtcp_tw_recycle\uff0c\u6545\u969c\u4e5f\u53ef\u4ee5\u89e3\u51b3\u3002\u63a8\u8350NAT\u73af\u5883\u4e0b\u7684\u673a\u5668\u4e0d\u8981\u5f00\u542f\u8be5\u9009\u9879\uff1b\n3) \u4e5f\u5c31\u662f\u8bf4\u8fd9\u4e24\u4e2a\u53c2\u6570\u4e0d\u53ef\u80fd\u540c\u65f6\u542f\u7528\u3002\n\n<strong>\u540e\u8bb0\uff1a<\/strong>\n1) \u5f53tcp_tw_recycle\u548ctcp_timestamps\u540c\u65f6\u6253\u5f00\u65f6\u4f1a\u6fc0\u6d3bTCP\u7684\u4e00\u79cd\u9690\u85cf\u5c5e\u6027\uff1a\u7f13\u5b58\u8fde\u63a5\u7684\u65f6\u95f4\u6233\u300260\u79d2\u5185\uff0c\u540c\u4e00\u6e90IP\u7684\u540e\u7eed\u8bf7\u6c42\u7684\u65f6\u95f4\u6233\u5c0f\u4e8e\u7f13\u5b58\u4e2d\u7684\u65f6\u95f4\u6233\uff0c\u5185\u6838\u5c31\u4f1a\u4e22\u5f03\u8be5\u8bf7\u6c42\u3002NAT\u53ea\u6539IP\u5730\u5740\u4fe1\u606f\uff0c\u4f46\u4e0d\u4f1a\u6539\u53d8timestamp<strong>\uff08TCP\u7684\u65f6\u95f4\u6233\u4e0d\u662f\u7cfb\u7edf\u65f6\u95f4\uff0c\u800c\u662f\u7cfb\u7edf\u542f\u52a8\u7684\u65f6\u95f4uptime\uff0c\u6240\u4ee5\u4e24\u53f0\u673a\u5668\u7684\u7684TCP\u65f6\u95f4\u6233\u4e00\u81f4\u7684\u53ef\u80fd\u6027\u5f88\u5c0f\uff09<\/strong>\uff0c\u6240\u4ee5\u5f88\u5bb9\u6613\u9020\u6210\u8fde\u63a5\u5931\u8d25\u7684\u60c5\u51b5\u3002\n\n2) TIME_WAIT\u72b6\u6001\u662f\u7528\u4e8e\u4fdd\u969c\u8fde\u63a5\u6b63\u5e38\u5173\u95ed\u7684\uff0c\u5e76\u4e0d\u4f1a\u6d88\u8017\u8fc7\u591a\u8d44\u6e90\u3002\u5728\u9ad8\u5e76\u53d1\u73af\u5883\u4e2dtcp_tw_recycle\u548ctcp_tw_reuse\u7ecf\u5e38\u88ab\u6253\u5f00\u7528\u6237\u5feb\u901f\u56de\u6536\u548c\u91cd\u7528TIME_WAIT\u72b6\u6001\u7684socket\uff0c\u5728\u8d44\u6e90\u6709\u9650\u7684\u60c5\u51b5\u4e0b\u8fd9\u4e48\u591a\u4e5f\u65e0\u53ef\u539a\u975e\uff0c\u4e0d\u8fc7\u4e5f\u5e94\u8be5\u77e5\u9053\u8fd9\u4e48\u505a\u4f1a\u5e26\u6765\u7684\u540e\u679c\u3002<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<header>\n<h1><\/h1>\n<h1>\u8bb0\u4e00\u6b21TIME_WAIT\u7f51\u7edc\u6545\u969c<\/h1>\n<\/header>\n<div>\n\n\u6700\u8fd1\u53d1\u73b0\u4e00\u4e2aPHP\u811a\u672c\u65f6\u5e38\u51fa\u73b0\u8fde\u4e0d\u4e0a\u670d\u52a1\u5668\u7684\u73b0\u8c61\uff0c\u8c03\u8bd5\u4e86\u4e00\u4e0b\uff0c\u53d1\u73b0\u662fTIME_WAIT\u72b6\u6001\u8fc7\u591a\u9020\u6210\u7684\uff0c\u672c\u6587\u7b80\u8981\u4ecb\u7ecd\u4e00\u4e0b\u89e3\u51b3\u95ee\u9898\u7684\u8fc7\u7a0b\u3002\n\n\u00a0\n\n\u9047\u5230\u8fd9\u7c7b\u95ee\u9898\uff0c\u6211\u4e60\u60ef\u4e8e\u5148\u7528strace\u547d\u4ee4\u8ddf\u8e2a\u4e86\u4e00\u4e0b\u770b\u770b\uff1a\n<pre>shell> strace php \/path\/to\/file\nEADDRNOTAVAIL (Cannot assign requested address)<\/pre>\n\u4ece\u5b57\u9762\u7ed3\u679c\u770b\u4f3c\u4e4e\u662f\u7f51\u7edc\u8d44\u6e90\u76f8\u5173\u95ee\u9898\u3002\u8fd9\u91cc\u987a\u4fbf\u4ecb\u7ecd\u4e00\u70b9\u5c0f\u6280\u5de7\uff1a\u5728\u8c03\u8bd5\u7684\u65f6\u5019\u4e00\u822c\u662f\u4ece\u540e\u5f80\u524d\u770bstrace\u547d\u4ee4\u7684\u7ed3\u679c\uff0c\u8fd9\u6837\u66f4\u5bb9\u6613\u627e\u5230\u6709\u4ef7\u503c\u7684\u4fe1\u606f\u3002\n\n\u67e5\u770b\u4e00\u4e0b\u5f53\u524d\u7684\u7f51\u7edc\u8fde\u63a5\u60c5\u51b5\uff0c\u7ed3\u679c\u53d1\u73b0TIME_WAIT\u6570\u975e\u5e38\u5927\uff1a\n<pre>shell> netstat -ant | awk '\n    {++s[$NF]} END {for(k in s) print k,s[k]}\n'<\/pre>\n\u8865\u5145\u4e00\u4e0b\uff0c\u540cnetstat\u76f8\u6bd4\uff0css\u8981\u5feb\u5f88\u591a\uff1a\n<pre>shell> ss -ant | awk '\n    {++s[$1]} END {for(k in s) print k,s[k]}\n'<\/pre>\n\u91cd\u590d\u4e86\u51e0\u6b21\u6d4b\u8bd5\uff0c\u7ed3\u679c\u6bcf\u6b21\u51fa\u95ee\u9898\u7684\u65f6\u5019\uff0cTIME_WAIT\u90fd\u7b49\u4e8e28233\uff0c\u8fd9\u771f\u662f\u4e00\u4e2a\u9b54\u6cd5\u6570\u5b57\uff01\u5b9e\u9645\u539f\u56e0\u5f88\u7b80\u5355\uff0c\u5b83\u53d6\u51b3\u4e8e\u4e00\u4e2a\u5185\u6838\u53c2\u6570net.ipv4.ip_local_port_range\uff1a\n<pre>shell> sysctl -a | grep port\nnet.ipv4.ip_local_port_range = 32768 61000<\/pre>\n\u56e0\u4e3a\u7aef\u53e3\u8303\u56f4\u662f\u4e00\u4e2a\u95ed\u533a\u95f4\uff0c\u6240\u4ee5\u5b9e\u9645\u53ef\u7528\u7684\u7aef\u53e3\u6570\u91cf\u662f\uff1a\n<pre>shell> echo $((61000-32768+1))\n28233<\/pre>\n\u95ee\u9898\u5206\u6790\u5230\u8fd9\u91cc\u57fa\u672c\u5c31\u6e05\u6670\u4e86\uff0c\u89e3\u51b3\u65b9\u5411\u4e5f\u660e\u786e\u4e86\uff0c\u5185\u5bb9\u6240\u9650\uff0c\u8fd9\u91cc\u5c31\u4e0d\u8bf4\u5982\u4f55\u4f18\u5316\u7a0b\u5e8f\u4ee3\u7801\u4e86\uff0c\u53ea\u662f\u4ece\u7cfb\u7edf\u65b9\u9762\u6765\u9610\u8ff0\u5982\u4f55\u89e3\u51b3\u95ee\u9898\uff0c\u65e0\u975e\u5c31\u662f\u4ee5\u4e0b\u4e24\u4e2a\u65b9\u9762\uff1a\n\n\u9996\u5148\u662f\u589e\u52a0\u672c\u5730\u53ef\u7528\u7aef\u53e3\u6570\u91cf\u3002\u8fd9\u70b9\u53ef\u4ee5\u7528\u4ee5\u4e0b\u547d\u4ee4\u6765\u5b9e\u73b0\uff1a\n<pre>shell> sysctl net.ipv4.ip_local_port_range=\"10240 61000\"<\/pre>\n\u5176\u6b21\u662f\u51cf\u5c11TIME_WAIT\u8fde\u63a5\u72b6\u6001\u3002\u7f51\u7edc\u4e0a\u5df2\u7ecf\u6709\u4e0d\u5c11\u76f8\u5173\u7684\u4ecb\u7ecd\uff0c\u5927\u591a\u662f\u5efa\u8bae\uff1a\n<pre>shell> sysctl net.ipv4.tcp_tw_reuse=1\nshell> sysctl net.ipv4.tcp_tw_recycle=1<\/pre>\n\u6ce8\uff1a\u901a\u8fc7sysctl\u547d\u4ee4\u4fee\u6539\u5185\u6838\u53c2\u6570\uff0c\u91cd\u542f\u540e\u4f1a\u8fd8\u539f\uff0c\u8981\u60f3\u6301\u4e45\u5316\u53ef\u4ee5\u53c2\u8003\u524d\u9762\u7684\u65b9\u6cd5\u3002\n\n\u8fd9\u4e24\u4e2a\u9009\u9879\u5728\u964d\u4f4eTIME_WAIT\u6570\u91cf\u65b9\u9762\u53ef\u4ee5\u8bf4\u662f\u7acb\u7aff\u89c1\u5f71\uff0c\u4e0d\u8fc7\u5982\u679c\u4f60\u89c9\u5f97\u95ee\u9898\u5df2\u7ecf\u5b8c\u7f8e\u641e\u5b9a\u90a3\u5c31\u9519\u4e86\uff0c\u5b9e\u9645\u4e0a\u8fd9\u6837\u53ef\u80fd\u4f1a\u5f15\u5165\u4e00\u4e2a\u66f4\u590d\u6742\u7684\u7f51\u7edc\u6545\u969c\u3002\n\n\u5173\u4e8e\u5185\u6838\u53c2\u6570\u7684\u8be6\u7ec6\u4ecb\u7ecd\uff0c\u53ef\u4ee5\u53c2\u8003<a href=\"http:\/\/www.kernel.org\/doc\/Documentation\/networking\/ip-sysctl.txt\" target=\"_blank\">\u5b98\u65b9\u6587\u6863<\/a>\u3002\u6211\u4eec\u8fd9\u91cc\u7b80\u8981\u8bf4\u660e\u4e00\u4e0btcp_tw_recycle\u53c2\u6570\u3002\u5b83\u7528\u6765\u5feb\u901f\u56de\u6536TIME_WAIT\u8fde\u63a5\uff0c\u4e0d\u8fc7\u5982\u679c\u5728NAT\u73af\u5883\u4e0b\u4f1a\u5f15\u53d1\u95ee\u9898\u3002\n\n<a href=\"http:\/\/tools.ietf.org\/html\/rfc1323\" target=\"_blank\">RFC1323<\/a>\u4e2d\u6709\u5982\u4e0b\u4e00\u6bb5\u63cf\u8ff0\uff1a\n<blockquote>An additional mechanism could be added to the TCP, a per-host\u00a0cache of the last timestamp received from any connection.\u00a0This value could then be used in the\u00a0<a href=\"http:\/\/tools.ietf.org\/html\/rfc1323#page-17\" target=\"_blank\">PAWS<\/a>\u00a0mechanism to reject\u00a0old duplicate segments from earlier incarnations of the\u00a0connection, if the timestamp clock can be guaranteed to have\u00a0ticked at least once since the old connection was open. This\u00a0would require that the TIME-WAIT delay plus the RTT together\u00a0must be at least one tick of the sender\u2019s timestamp clock.\u00a0Such an extension is not part of the proposal of this RFC.<\/blockquote>\n\u5927\u6982\u610f\u601d\u662f\u8bf4TCP\u6709\u4e00\u79cd\u884c\u4e3a\uff0c\u53ef\u4ee5\u7f13\u5b58\u6bcf\u4e2a\u8fde\u63a5\u6700\u65b0\u7684\u65f6\u95f4\u6233\uff0c\u540e\u7eed\u8bf7\u6c42\u4e2d\u5982\u679c\u65f6\u95f4\u6233\u5c0f\u4e8e\u7f13\u5b58\u7684\u65f6\u95f4\u6233\uff0c\u5373\u89c6\u4e3a\u65e0\u6548\uff0c\u76f8\u5e94\u7684\u6570\u636e\u5305\u4f1a\u88ab\u4e22\u5f03\u3002\n\nLinux\u662f\u5426\u542f\u7528\u8fd9\u79cd\u884c\u4e3a\u53d6\u51b3\u4e8etcp_timestamps\u548ctcp_tw_recycle\uff0c\u56e0\u4e3atcp_timestamps\u7f3a\u7701\u5c31\u662f\u5f00\u542f\u7684\uff0c\u6240\u4ee5\u5f53tcp_tw_recycle\u88ab\u5f00\u542f\u540e\uff0c\u5b9e\u9645\u4e0a\u8fd9\u79cd\u884c\u4e3a\u5c31\u88ab\u6fc0\u6d3b\u4e86\uff0c\u5f53\u5ba2\u6237\u7aef\u6216\u670d\u52a1\u7aef\u4ee5NAT\u65b9\u5f0f\u6784\u5efa\u7684\u65f6\u5019\u5c31\u53ef\u80fd\u51fa\u73b0\u95ee\u9898\uff0c\u4e0b\u9762\u4ee5\u5ba2\u6237\u7aefNAT\u4e3a\u4f8b\u6765\u8bf4\u660e\uff1a\n\n\u5f53\u591a\u4e2a\u5ba2\u6237\u7aef\u901a\u8fc7NAT\u65b9\u5f0f\u8054\u7f51\u5e76\u4e0e\u670d\u52a1\u7aef\u4ea4\u4e92\u65f6\uff0c\u670d\u52a1\u7aef\u770b\u5230\u7684\u662f\u540c\u4e00\u4e2aIP\uff0c\u4e5f\u5c31\u662f\u8bf4\u5bf9\u670d\u52a1\u7aef\u800c\u8a00\u8fd9\u4e9b\u5ba2\u6237\u7aef\u5b9e\u9645\u4e0a\u7b49\u540c\u4e8e\u4e00\u4e2a\uff0c\u53ef\u60dc\u7531\u4e8e\u8fd9\u4e9b\u5ba2\u6237\u7aef\u7684\u65f6\u95f4\u6233\u53ef\u80fd\u5b58\u5728\u5dee\u5f02\uff0c\u4e8e\u662f\u4e4e\u4ece\u670d\u52a1\u7aef\u7684\u89c6\u89d2\u770b\uff0c\u4fbf\u53ef\u80fd\u51fa\u73b0\u65f6\u95f4\u6233\u9519\u4e71\u7684\u73b0\u8c61\uff0c\u8fdb\u800c\u76f4\u63a5\u5bfc\u81f4\u65f6\u95f4\u6233\u5c0f\u7684\u6570\u636e\u5305\u88ab\u4e22\u5f03\u3002\u5982\u679c\u53d1\u751f\u4e86\u6b64\u7c7b\u95ee\u9898\uff0c\u5177\u4f53\u7684\u8868\u73b0\u901a\u5e38\u662f\u662f\u5ba2\u6237\u7aef\u660e\u660e\u53d1\u9001\u7684SYN\uff0c\u4f46\u670d\u52a1\u7aef\u5c31\u662f\u4e0d\u54cd\u5e94ACK\uff0c\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u4e0b\u9762\u547d\u4ee4\u6765\u786e\u8ba4\u6570\u636e\u5305\u4e0d\u65ad\u88ab\u4e22\u5f03\u7684\u73b0\u8c61\uff1a\n<pre>shell> netstat -s | grep timestamp\n... packets rejects in established connections because of timestamp<\/pre>\n\u5b89\u5168\u8d77\u89c1\uff0c\u901a\u5e38\u8981\u7981\u6b62tcp_tw_recycle\u3002\u8bf4\u5230\u8fd9\u91cc\uff0c\u5927\u5bb6\u53ef\u80fd\u4f1a\u60f3\u5230\u53e6\u4e00\u79cd\u89e3\u51b3\u65b9\u6848\uff1a\u628atcp_timestamps\u8bbe\u7f6e\u4e3a0\uff0ctcp_tw_recycle\u8bbe\u7f6e\u4e3a1\uff0c\u8fd9\u6837\u4e0d\u5c31\u53ef\u4ee5\u9c7c\u4e0e\u718a\u638c\u517c\u5f97\u4e86\u4e48\uff1f\u53ef\u60dc\u4e00\u65e6\u5173\u95ed\u4e86tcp_timestamps\uff0c\u90a3\u4e48\u5373\u4fbf\u6253\u5f00\u4e86tcp_tw_recycle\uff0c\u4e5f\u6ca1\u6709\u6548\u679c\u3002\n\n\u597d\u5728\u6211\u4eec\u8fd8\u6709\u53e6\u4e00\u4e2a\u5185\u6838\u53c2\u6570tcp_max_tw_buckets\uff08\u4e00\u822c\u7f3a\u7701\u662f180000\uff09\u53ef\u7528\uff1a\n<pre>shell> sysctl net.ipv4.tcp_max_tw_buckets=10000<\/pre>\n\u901a\u8fc7\u8bbe\u7f6e\u5b83\uff0c\u7cfb\u7edf\u4f1a\u5c06\u591a\u4f59\u7684TIME_WAIT\u5220\u9664\u6389\uff0c\u6b64\u65f6\u7cfb\u7edf\u65e5\u5fd7\u91cc\u53ef\u80fd\u4f1a\u663e\u793a\uff1a\u300cTCP: time wait bucket table overflow\u300d\uff0c\u591a\u6570\u60c5\u51b5\u4e0b\u4e0d\u7528\u592a\u5728\u610f\u8fd9\u4e9b\u4fe1\u606f\u3002\n\n\u2026\n\n\u603b\u4f53\u6765\u8bf4\uff0c\u8fd9\u6b21\u7f51\u7edc\u6545\u969c\u672c\u8eab\u5e76\u6ca1\u4ec0\u4e48\u9ad8\u6df1\u4e4b\u5904\uff0c\u672c\u4e0d\u60f3\u7f57\u7f57\u55e6\u55e6\u5199\u8fd9\u4e48\u591a\uff0c\u4e0d\u8fc7\u62d4\u51fa\u841d\u535c\u5e26\u51fa\u6ce5\uff0c\u5728\u8fc7\u7a0b\u4e2d\u7275\u626f\u7684\u65b9\u65b9\u9762\u9762\u8fd8\u662f\u503c\u5f97\u5927\u5bb6\u54c1\u5473\u7684\uff0c\u4e8e\u662f\u4fbf\u6709\u4e86\u8fd9\u7bc7\u6587\u5b57\u3002\n\n<\/div>","protected":false},"excerpt":{"rendered":"<p>\u8fd1\u6765\u7ebf\u4e0a\u9646\u7eed\u51fa\u73b0\u4e86\u4e00\u4e9bconnect\u5931\u8d25\u7684\u95ee\u9898\uff0c\u7ecf\u8fc7\u5206\u6790\u8bd5\u9a8c\uff0c\u6700\u7ec8\u786e\u8ba4\u548cproc\u53c2\u6570tcp_tw_recycle\/tcp_timestamps\u76f8\u5173\uff1b \u73b0\u8c61 \u7b2c\u4e00\u4e2a\u73b0\u8c61\uff1a\u6a21\u5757A\u901a\u8fc7NAT\u7f51\u5173\u8bbf\u95ee\u670d\u52a1S\u6210&#46;&#46;&#46;<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[372,371,370],"class_list":["post-1162","post","type-post","status-publish","format-standard","hentry","category-linux","tag-tcp_max_tw_buckets","tag-tcp_timestamps","tag-tcp_tw_recycle"],"_links":{"self":[{"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/posts\/1162","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/comments?post=1162"}],"version-history":[{"count":4,"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/posts\/1162\/revisions"}],"predecessor-version":[{"id":1164,"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/posts\/1162\/revisions\/1164"}],"wp:attachment":[{"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/media?parent=1162"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/categories?post=1162"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/nick.txtcc.com\/index.php\/wp-json\/wp\/v2\/tags?post=1162"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}