1 | #include <sys/socket.h>
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2 | #include <netinet/in.h>
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3 | #include <netdb.h>
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4 | #include <arpa/inet.h>
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5 | #include <stdint.h>
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6 | #include <string.h>
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7 | #include <poll.h>
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8 | #include <time.h>
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9 | #include <ctype.h>
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10 | #include <unistd.h>
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11 | #include <errno.h>
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12 | #include <pthread.h>
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13 | #include "stdio_impl.h"
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14 | #include "syscall.h"
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15 | #include "lookup.h"
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16 |
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17 | static void cleanup(void *p)
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18 | {
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19 | __syscall(SYS_close, (intptr_t)p);
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20 | }
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21 |
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22 | static unsigned long mtime()
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23 | {
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24 | struct timespec ts;
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25 | clock_gettime(CLOCK_REALTIME, &ts);
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26 | return (unsigned long)ts.tv_sec * 1000
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27 | + ts.tv_nsec / 1000000;
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28 | }
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29 |
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30 | int __res_msend_rc(int nqueries, const unsigned char *const *queries,
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31 | const int *qlens, unsigned char *const *answers, int *alens, int asize,
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32 | const struct resolvconf *conf)
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33 | {
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34 | int fd;
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35 | int timeout, attempts, retry_interval, servfail_retry;
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36 | union {
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37 | struct sockaddr_in sin;
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38 | struct sockaddr_in6 sin6;
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39 | } sa = {0}, ns[MAXNS] = {{0}};
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40 | socklen_t sl = sizeof sa.sin;
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41 | int nns = 0;
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42 | int family = AF_INET;
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43 | int rlen;
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44 | int next;
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45 | int i, j;
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46 | int cs;
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47 | struct pollfd pfd;
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48 | unsigned long t0, t1, t2;
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49 |
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50 | pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
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51 |
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52 | timeout = 1000*conf->timeout;
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53 | attempts = conf->attempts;
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54 |
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55 | for (nns=0; nns<conf->nns; nns++) {
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56 | const struct address *iplit = &conf->ns[nns];
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57 | if (iplit->family == AF_INET) {
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58 | memcpy(&ns[nns].sin.sin_addr, iplit->addr, 4);
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59 | ns[nns].sin.sin_port = htons(53);
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60 | ns[nns].sin.sin_family = AF_INET;
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61 | } else {
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62 | sl = sizeof sa.sin6;
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63 | memcpy(&ns[nns].sin6.sin6_addr, iplit->addr, 16);
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64 | ns[nns].sin6.sin6_port = htons(53);
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65 | ns[nns].sin6.sin6_scope_id = iplit->scopeid;
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66 | ns[nns].sin6.sin6_family = family = AF_INET6;
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67 | }
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68 | }
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69 |
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70 | /* Get local address and open/bind a socket */
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71 | sa.sin.sin_family = family;
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72 | fd = socket(family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
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73 |
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74 | /* Handle case where system lacks IPv6 support */
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75 | if (fd < 0 && family == AF_INET6 && errno == EAFNOSUPPORT) {
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76 | fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0);
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77 | family = AF_INET;
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78 | }
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79 | if (fd < 0 || bind(fd, (void *)&sa, sl) < 0) {
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80 | if (fd >= 0) close(fd);
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81 | pthread_setcancelstate(cs, 0);
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82 | return -1;
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83 | }
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84 |
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85 | /* Past this point, there are no errors. Each individual query will
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86 | * yield either no reply (indicated by zero length) or an answer
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87 | * packet which is up to the caller to interpret. */
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88 |
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89 | pthread_cleanup_push(cleanup, (void *)(intptr_t)fd);
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90 | pthread_setcancelstate(cs, 0);
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91 |
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92 | /* Convert any IPv4 addresses in a mixed environment to v4-mapped */
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93 | if (family == AF_INET6) {
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94 | setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &(int){0}, sizeof 0);
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95 | for (i=0; i<nns; i++) {
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96 | if (ns[i].sin.sin_family != AF_INET) continue;
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97 | memcpy(ns[i].sin6.sin6_addr.s6_addr+12,
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98 | &ns[i].sin.sin_addr, 4);
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99 | memcpy(ns[i].sin6.sin6_addr.s6_addr,
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100 | "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
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101 | ns[i].sin6.sin6_family = AF_INET6;
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102 | ns[i].sin6.sin6_flowinfo = 0;
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103 | ns[i].sin6.sin6_scope_id = 0;
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104 | }
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105 | }
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106 |
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107 | memset(alens, 0, sizeof *alens * nqueries);
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108 |
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109 | pfd.fd = fd;
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110 | pfd.events = POLLIN;
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111 | retry_interval = timeout / attempts;
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112 | next = 0;
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113 | t0 = t2 = mtime();
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114 | t1 = t2 - retry_interval;
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115 |
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116 | for (; t2-t0 < timeout; t2=mtime()) {
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117 | if (t2-t1 >= retry_interval) {
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118 | /* Query all configured namservers in parallel */
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119 | for (i=0; i<nqueries; i++)
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120 | if (!alens[i])
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121 | for (j=0; j<nns; j++)
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122 | sendto(fd, queries[i],
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123 | qlens[i], MSG_NOSIGNAL,
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124 | (void *)&ns[j], sl);
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125 | t1 = t2;
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126 | servfail_retry = 2 * nqueries;
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127 | }
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128 |
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129 | /* Wait for a response, or until time to retry */
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130 | if (poll(&pfd, 1, t1+retry_interval-t2) <= 0) continue;
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131 |
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132 | while ((rlen = recvfrom(fd, answers[next], asize, 0,
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133 | (void *)&sa, (socklen_t[1]){sl})) >= 0) {
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134 |
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135 | /* Ignore non-identifiable packets */
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136 | if (rlen < 4) continue;
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137 |
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138 | /* Ignore replies from addresses we didn't send to */
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139 | for (j=0; j<nns && memcmp(ns+j, &sa, sl); j++);
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140 | if (j==nns) continue;
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141 |
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142 | /* Find which query this answer goes with, if any */
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143 | for (i=next; i<nqueries && (
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144 | answers[next][0] != queries[i][0] ||
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145 | answers[next][1] != queries[i][1] ); i++);
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146 | if (i==nqueries) continue;
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147 | if (alens[i]) continue;
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148 |
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149 | /* Only accept positive or negative responses;
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150 | * retry immediately on server failure, and ignore
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151 | * all other codes such as refusal. */
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152 | switch (answers[next][3] & 15) {
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153 | case 0:
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154 | case 3:
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155 | break;
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156 | case 2:
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157 | if (servfail_retry && servfail_retry--)
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158 | sendto(fd, queries[i],
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159 | qlens[i], MSG_NOSIGNAL,
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160 | (void *)&ns[j], sl);
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161 | default:
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162 | continue;
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163 | }
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164 |
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165 | /* Store answer in the right slot, or update next
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166 | * available temp slot if it's already in place. */
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167 | alens[i] = rlen;
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168 | if (i == next)
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169 | for (; next<nqueries && alens[next]; next++);
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170 | else
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171 | memcpy(answers[i], answers[next], rlen);
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172 |
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173 | if (next == nqueries) goto out;
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174 | }
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175 | }
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176 | out:
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177 | pthread_cleanup_pop(1);
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178 |
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179 | return 0;
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180 | }
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181 |
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182 | int __res_msend(int nqueries, const unsigned char *const *queries,
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183 | const int *qlens, unsigned char *const *answers, int *alens, int asize)
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184 | {
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185 | struct resolvconf conf;
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186 | if (__get_resolv_conf(&conf, 0, 0) < 0) return -1;
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187 | return __res_msend_rc(nqueries, queries, qlens, answers, alens, asize, &conf);
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188 | }
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