{"id":1998,"date":"2019-03-08T14:04:43","date_gmt":"2019-03-08T06:04:43","guid":{"rendered":"http:\/\/ufqi.com\/blog\/?p=1998"},"modified":"2019-03-10T19:37:27","modified_gmt":"2019-03-10T11:37:27","slug":"devops-iptables-ddos-tablefull","status":"publish","type":"post","link":"https:\/\/ufqi.com\/blog\/devops-iptables-ddos-tablefull\/","title":{"rendered":"DevOps: \u4e00\u4f8b\u9ad8\u8d1f\u8f7d\u591a\u5e76\u53d1\u670d\u52a1\u5668\u8fde\u63a5\u6c60\u6ee1\u7684\u5f02\u5e38\u6392\u89e3\u8fc7\u7a0b"},"content":{"rendered":"

\u4eca\u5929\u662f\u4e09\u516b\u56fd\u9645\u5987\u5973\u8282, \u4e5f\u662f\u4e2d\u56fd\u519c\u5386\u4e8c\u6708\u4e8c\/\u9f99\u62ac\u5934\u7684\u8282\u65e5\uff0c\u606d\u795d\u5973\u540c\u80de\u8282\u65e5\u5feb\u4e50\uff01\u606d\u795d\u4e2d\u56fd\u5584\u826f\u7684\u4eba\u4eec\u90fd\u62ac\u5934\u89c1\u559c!<\/p>\n

\u597d\u4e00\u9635\u5b50\u6ca1\u66f4\u65b0Blog\uff0c\u4eca\u5929\u4e5f\u501f\u8fd9\u559c\u6c14\u51b2\u5237\u4e00\u4e0b\u5f80\u65e5\u7684\u9634\u973e\uff0c\u7ecf\u8fc7\u591a\u65e5\u7684\u89c2\u5bdf\uff0c\u7ec8\u4e8e\u627e\u5230\u8fd9\u9635\u5b50\u201c\u6709\u798f\u65b0\u95fb\u201d\u9ad8\u8d1f\u8f7d\u591a\u5e76\u53d1\u670d\u52a1\u5668\u7684\u5f02\u5e38\u62a5\u9519\u80cc\u540e\u7684\u539f\u56e0\u4e4b\u4e00\u3002\u6b64\u524d\u5728Blog\u4e2d\u9891\u7e41\u89c2\u6d4b\u5230 GWA2 PHP Memcached\u7684\u62a5\u9519\uff0c\u5e76\u4e14\u5728\u4ee3\u7801\u5c42\u9762\u8fdb\u884c\u4e86\u591a\u6b21\u8c03\u4f18\uff0c\u95ee\u9898\u6682\u65f6\u5f97\u5230\u7f13\u89e3\uff0c\u6df1\u5c42\u5e76\u672a\u6df1\u7a76\u51fa\u4e2a\u6240\u4ee5\u7136\u3002<\/p>\n

\n

\u201cGWA2 PHP Memcached\u81ea\u52a8\u8ffd\u52a0\u670d\u52a1\u5668\u8fde\u63a5\uff1f\u4e00\u4f8b\u7f13\u5b58\u670d\u52a1\u88ab\u51fb\u7a7f\u7684\u5f02\u5e38\u5206\u6790\u201d\uff0c\u00a0-R\/52SP<\/a>\u00a0 \u3002<\/p>\n<\/blockquote>\n

\u5728\u8fdb\u884c\u65e5\u5e38\u670d\u52a1\u5668\u72b6\u6001\u5de1\u68c0\u65f6\uff0c\u5148\u662f\u53d1\u73b0 Apache \u5728\u6570\u65e5\u7684\u6301\u7eed\u8fd0\u884c\u4e2d\uff0c\u4f1a\u6709 segmentation fault \u5bfc\u81f4\u7684\u6b7b\u6389\uff0c\u4e8e\u662f\u5bf9 Apache 2.4.x \u8fdb\u884c\u5347\u7ea7\u5230\u6700\u65b0\u7248\u7684\u64cd\u4f5c\uff0c\u7136\u800c\u52a0\u4e86\u4fdd\u62a4\u63aa\u65bd\u3002\u5c3d\u7ba1\u5076\u5c14\u6709 Apache child \u6709 segmentation fault\u9000\u51fa\uff0c\u4f46\u6574\u4e2a\u670d\u52a1\u987d\u5f3a\u7684\u6d3b\u7740.<\/p>\n

\u540e\u7eed\u51e0\u65e5\u7684\u8fde\u7eed\u89c2\u6d4b\u4e2d\uff0cApache\u6682\u65e0\u5f02\u5e38\u6b7b\u6389\uff0c\u800c GWA2 PHP Memcached\u518d\u6b21\u5f00\u59cb\u62a5\u9519\uff0c\u62a5\u9519\u4fe1\u606f\u4e3a\u552f\u4e00\u7684 127.0.0.1\/11211 \u670d\u52a1\u88ab\u6807\u8bb0\u4e3a DEAD (error code: 35). \u7136\u800c\u5728\u7ec8\u7aef\u7528 telnet \u8fdb\u884c\u624b\u5de5\u6a21\u62df\u65f6\uff0cmemcached\u7684\u670d\u52a1\u53c8\u662f\u6b63\u5e38\u7684\uff0c\u8fd9\u662f\u4e3a\u4f55\uff1f\u65f6\u597d\u65f6\u574f\uff0c\u968f\u673a\u51fa\u9519\u5417\uff1f<\/p>\n

\u8fd1\u65e5\u7ee7\u7eed\u63a2\u6d4b\uff0c\u5728\u6700\u8fd1\u7684\u4e00\u6b21\u670d\u52a1\u5668\u4e0a\u5c1d\u8bd5\u4f7f\u7528 ping ufqi.com \u65f6\uff0c\u547d\u4ee4\u884c\u5f00\u59cb\u62a5\u9519\u8bf4 sendmeg not permitted… \u4e8e\u662f\u4e00\u4f8b\u670d\u52a1\u5668\u64cd\u4f5c\u7cfb\u7edf\u5c42\u9762\u7684\u95ee\u9898\u88ab\u66dd\u9732\u51fa\u6765\u3002<\/p>\n

ping\u547d\u4ee4\u7684\u65e0\u6cd5\u6267\u884c\uff0c\u53ef\u80fd\u662f\u7f51\u7edc\u914d\u7f6e\u6216\u64cd\u4f5c\u7cfb\u7edf\u5f02\u5e38\uff0c\u5faa\u7740\u8fd9\u4e2a\u601d\u8def\uff0c\u6211\u4eec\u4f7f\u7528 journalctl -f \u547d\u4ee4\uff0c\u5f88\u5feb\u770b\u5230 kernel\u5c42\u7684\u62a5\u9519\u4fe1\u606f\uff1a<\/p>\n

\n

Mar 08 04:43:06 srv21 kernel: nf_conntrack: nf_conntrack: table full, dropping packet
Mar 08 04:43:06 srv21 kernel: nf_conntrack: nf_conntrack: table full, dropping packet
Mar 08 04:43:06 srv21 kernel: nf_conntrack: nf_conntrack: table full, dropping packet<\/p>\n<\/blockquote>\n

\u539f\u6765\u662f\u7cfb\u7edf\u7684\u7f51\u7edc\u8fde\u63a5\u6c60\u51fa\u73b0\u4e86\u95ee\u9898\uff01\u5173\u4e8e \u201cnf_conntrack: table full, dropping packet\u201d \u8fd9\u91cc\u00a0-R\/u2SR<\/a>\u00a0<\/b>\u6709\u8be6\u7ec6\u7684\u89e3\u91ca\u3002\u00a0\u7b80\u5355\u5730\u8bf4\uff0c\u64cd\u4f5c\u7cfb\u7edf\u96c6\u6210\u4e86 Netfilter \u9632\u706b\u5899\u670d\u52a1\uff0c\u57fa\u4e8e iptables \u7684\u64cd\u4f5c\u7cfb\u7edf\u7684\u8fde\u63a5\u7ba1\u7406\u5668\u4e2d\uff0c\u6709\u56db\u4e2a table\uff08\u8868\uff09 \u548c\u4e94\u4e2a chain\uff08\u94fe\uff09\u3002<\/p>\n


Fig1. Iptables 4 tables and 5 chains<\/p>\n

\n

Tables: categorized by different operations to data packets.<\/strong><\/p>\n

raw<\/code>: highest priority, only appied to\u00a0PREROUTING<\/code>\u00a0and\u00a0OUTPUT<\/code>\u00a0chain. When we don\u2019t need to do NAT, we can use RAW table to increase performance.<\/p>\n

mangle<\/code>: modify certain data packet<\/p>\n

nat<\/code>: NAT, port mapping, address mapping<\/p>\n

filter<\/code>: filter<\/p>\n

Chains: categorized by different hooks.<\/strong><\/p>\n

PREROUTING<\/code>: packet before going to route table<\/p>\n

INPUT<\/code>: after packet passing route table, destination is current machine<\/p>\n

FORWARDING<\/code>: after packet passing route table, destination is not current machine<\/p>\n

OUTPUT<\/code>: packet comes from current machine and to outside<\/p>\n

POSTROUTIONG<\/code>: packet before going to network interface<\/p>\n<\/blockquote>\n

\u5f53\u64cd\u4f5c\u7cfb\u7edf\u5904\u7406 TCP\/IP \u8fde\u63a5\u76f8\u5173\u6a21\u5757\u51fa\u9519\u65f6\uff0c\u6240\u6709\u57fa\u4e8e\u8fde\u63a5\u7684\u670d\u52a1\u90fd\u4f1a\u62a5\u51fa\u5f02\u5e38\u3002\u8fd9\u662f\u6b64\u524d\u5728\u4ee3\u7801\u5c42\u65e0\u8bba\u5982\u4f55\u4f18\u5316\u90fd\u6ca1\u529e\u6cd5\u89e3\u51b3OSI\u5206\u5c42\u4e2d\u66f4\u5e95\u5c42\u7684\u95ee\u9898\u3002<\/p>\n

\u64cd\u4f5c\u7cfb\u7edf\u9ed8\u8ba4\u7684\u5e76\u53d1\u8fde\u63a5\u6570\u4e3a 65535\uff0c \u901a\u8fc7\u547d\u4ee4\uff1acat \/proc\/sys\/net\/netfilter\/nf_conntrack_max\u00a0 \u53ef\u4ee5\u67e5\u770b\u5230\u3002 \u5982\u679c\u901a\u8fc7\u547d\u4ee4\u00a0cat \/proc\/sys\/net\/netfilter\/nf_conntrack_count \u83b7\u5f97\u5230\u7684\u6570\u5b57\u7b49\u4e8e max \u7684\u6700\u5927\u503c\u65f6\uff0c\u6b64\u65f6\u518d\u6709\u65b0\u521b\u5efa\u8fde\u63a5\u7684\u9700\u6c42\u5c31\u4f1a\u62a5\u9519\uff0c\u5f53\u521b\u5efa\u8fde\u63a5\u5931\u8d25\u65f6\uff0c\u57fa\u4e8e\u5176\u4e0a\u7684\u6240\u6709\u5e94\u7528\u90fd\u5c06\u5931\u8d25\uff0c\u800c\u8fd9\u4e9b\u5728\u4ee3\u7801\u5c42\u5e76\u4e0d\u5bb9\u6613\u89e3\u51b3\u3002\u63a8\u8350\u7684\u00a0\/proc\/sys\/net\/netfilter\/nf_conntrack_max \u503c\u7684\u8ba1\u7b97\u516c\u5f0f\uff1a CONNTRACK_MAX = RAMSIZE (in bytes) \/ 16384 \/ (ARCH \/ 32) \uff0c \u5982\u00a08GB RAM in x86_64 OS,\u00a0\u00a0max =\u00a08*1024^3\/16384\/2=262144 \u3002<\/code><\/p>\n

\u5f53\u4e00\u53f0\u7e41\u5fd9\u7684\u670d\u52a1\u5668\u7684\u8fde\u63a5\u6570\u8d85\u8fc7\u9ed8\u8ba4\u503c\u65f6\uff0c\u9700\u8981\u901a\u8fc7\u4fee\u6539\u00a0\/proc\/sys\/net\/netfilter\/nf_conntrack_max\u00a0 \u6765\u4f7f\u5f97\u7cfb\u7edf\u80fd\u591f\u63a5\u6536\u66f4\u591a\u8fde\u63a5\u8fdb\u6765\u3002<\/p>\n

\u4e34\u65f6\u4fee\u6539\uff1a
echo 524288 > \/proc\/sys\/net\/netfilter\/nf_conntrack_max
or
sysctl -w net.netfilter.nf_conntrack_max=262144
\u6c38\u4e45\u4fee\u6539\uff1a
\u5728\u00a0\/etc\/rc.d\/after.local\u00a0 \u6216\u8005\u00a0\/etc\/rc.d\/rc.local \u4e2d\u589e\u52a0\u4e0a\u8ff0\u547d\u4ee4\u884c\u8bed\u53e5\u3002<\/p>\n

\u9664\u4e86\u589e\u52a0\u00a0\/proc\/sys\/net\/netfilter\/nf_conntrack_max \u53c2\u6570\u8bbe\u5b9a\u5916\uff0c\u8fd8\u53ef\u4ee5\u901a\u8fc7\u8c03\u6574 iptables \u7684\u8868\u6216\u8005\u94fe\u4e0a\u76f8\u5173\u89c4\u5219\u6765\u8fdb\u884c\u8c03\u4f18\uff0c\u66f4\u591a\u53c2\u8003\uff1a\u00a0-R\/u2SR<\/a>\u00a0\u3002<\/b><\/p>\n

\u201c\u6709\u798f\u65b0\u95fb\u201d\uff0c \u201c\u5168\u56fd\u62db\u6295\u6807\u4fe1\u606f\u4e2d\u5fc3\u201d \u7b49\u670d\u52a1\u53c8\u53ef\u4ee5\u7545\u5feb\u5730\u8fd0\u884c\u5e76\u6709\u4fe1\u5fc3\u5730\u8fce\u63a5\u4e0b\u4e00\u6b21\u6d2a\u5cf0\u7684\u5230\u6765\u3002<\/p>\n

\u5c0f\u7ed3\uff1a
1. \u5728\u4ee3\u7801\u5c42\u5f88\u96be\u53d1\u73b0\u64cd\u4f5c\u7cfb\u7edf\u5c42\u7684\u95ee\u9898\uff0c\u53ef\u884c\u7684\u8def\u7ebf\u662f\u5206\u6790\u5e94\u7528\u5c42\u6e90\u7801\uff1b
2. \u7cfb\u7edf\u5c42\u7684\u5f02\u5e38\uff0c\u901a\u8fc7\u5177\u6709\u968f\u673a\u6027\uff0c\u6bd4\u5982\u8fde\u63a5\u6570\uff0c\u662f\u4e00\u4e2a\u52a8\u6001\u53d8\u5316\u6570\u636e\uff0c\u53ef\u80fd\u4e0b\u4e00\u79d2\u5f02\u5e38\u5c31\u6ca1\u6709\u4e86\uff0c\u65e0\u6cd5\u786e\u5b9a\u91cd\u73b0\u7684\u95ee\u9898\u4e3a troubleshooting \u5e26\u6765\u4e86\u4e00\u5b9a\u7684\u969c\u788d\u3002
\u4f46\u662f\uff0c\u5df2\u6709\u7684\u95ee\u9898\uff0c\u5728\u6ca1\u89e3\u51b3\u4e4b\u524d\uff0c\u4f1a\u518d\u6b21\u53d1\u751f\uff0c\u8fd9\u662f\u786e\u5b9a\u7684\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

\u4eca\u5929\u662f\u4e09\u516b\u56fd\u9645\u5987\u5973\u8282, \u4e5f\u662f\u4e2d\u56fd\u519c\u5386\u4e8c\u6708\u4e8c\/\u9f99\u62ac\u5934\u7684\u8282\u65e5\uff0c\u606d\u795d\u5973\u540c\u80de\u8282\u65e5\u5feb\u4e50\uff01\u606d … \u7ee7\u7eed\u9605\u8bfb →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[42,7,2],"tags":[86,303,302,304,305],"_links":{"self":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts\/1998"}],"collection":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/comments?post=1998"}],"version-history":[{"count":8,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts\/1998\/revisions"}],"predecessor-version":[{"id":2009,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts\/1998\/revisions\/2009"}],"wp:attachment":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/media?parent=1998"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/categories?post=1998"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/tags?post=1998"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}