Android DNS 代碼分析
Android DNS 代碼都在bionic/libc/netbsd中
(雖然netbsd 是個(gè)廢棄的項(xiàng)目，但dns功能部分代碼被 Android用上了)
netbsd 代碼晦澀難懂，只有一邊寫程序，一邊打log驗(yàn)證
照抄了一個(gè)簡(jiǎn)單程序， 在android 下面用 mmm 編譯可以得到 py_getaddr 可執(zhí)行文件， 用adb 登陸到 devices 再到 system/bin 下去執(zhí)行
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payne@payne-desktop:~/njb/getaddr$ cat py_getaddr.c #include <stdio.h>#include <stdlib.h>#include <sys socket.h="">#include <netinet in.h="">#include <netdb.h>#include <string.h>int main(int argc, char **argv){if (argc != 2) {fprintf(stderr, "Usage: %s hostnamen",argv[1]);exit(1); }struct addrinfo *answer, hint, *curr;char ipstr[16]; bzero(&hint, sizeof(hint));hint.ai_family = AF_INET;hint.ai_socktype = SOCK_STREAM;int ret = getaddrinfo(argv[1], NULL, &hint, &answer);if (ret != 0) {fprintf(stderr,"getaddrinfo: &sn",gai_strerror(ret));exit(1);}for (curr = answer; curr != NULL; curr = curr->ai_next) {inet_ntop(AF_INET,&(((struct sockaddr_in *)(curr->ai_addr))->sin_addr),ipstr, 16);printf("%sn", ipstr);}freeaddrinfo(answer);exit(0);}</string.h></netdb.h></netinet></sys></stdlib.h></stdio.h> |
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cat Android.mk LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_SRC_FILES:= py_getaddr.cLOCAL_MODULE := py_getaddrLOCAL_STATIC_LIBRARIES := libcutils libcinclude $(BUILD_EXECUTABLE) |
到運(yùn)行 py_getadd sohu.com 的時(shí)候， 調(diào)用過程如下
_files_getaddrinfo 是讀取/system/etc/hosts 檢索<喎�"http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">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"http://www.2cto.com/uploadfile/Collfiles/20141126/20141126084453260.png" alt="">
運(yùn)行程序和 log 的打印結(jié)果如下：
py_getaddr sohu.com
======================= _files_getaddrinfo
======================= _dns_getaddrinfo
=========== getaddrinfo cp 8.8.8.8, subf 53
================ res_searchN sohu.com
================ res_querydomainN name sohu.com, domain (null)
================ res_queryN sohu.com
;; res_nmkquery(QUERY, sohu.com, IN, A)
================getanswer sohu.com
220.181.90.240
123.125.116.19
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