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 <net/if.h>
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5 | #include <arpa/inet.h>
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6 | #include <ctype.h>
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7 | #include <stdlib.h>
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8 | #include <string.h>
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9 | #include <fcntl.h>
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10 | #include <unistd.h>
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11 | #include <pthread.h>
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12 | #include <errno.h>
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13 | #include "lookup.h"
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14 | #include "stdio_impl.h"
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15 | #include "syscall.h"
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16 |
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17 | static int is_valid_hostname(const char *host)
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18 | {
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19 | const unsigned char *s;
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20 | if (strnlen(host, 255)-1 >= 254 || mbstowcs(0, host, 0) == -1) return 0;
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21 | for (s=(void *)host; *s>=0x80 || *s=='.' || *s=='-' || isalnum(*s); s++);
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22 | return !*s;
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23 | }
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24 |
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25 | static int name_from_null(struct address buf[static 2], const char *name, int family, int flags)
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26 | {
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27 | int cnt = 0;
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28 | if (name) return 0;
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29 | if (flags & AI_PASSIVE) {
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30 | if (family != AF_INET6)
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31 | buf[cnt++] = (struct address){ .family = AF_INET };
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32 | /*if (family != AF_INET)
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33 | buf[cnt++] = (struct address){ .family = AF_INET6 };*/
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34 | } else {
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35 | if (family != AF_INET6)
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36 | buf[cnt++] = (struct address){ .family = AF_INET, .addr = { 127,0,0,1 } };
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37 | /*if (family != AF_INET)
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38 | buf[cnt++] = (struct address){ .family = AF_INET6, .addr = { [15] = 1 } };*/
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39 | }
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40 | return cnt;
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41 | }
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42 |
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43 | static int name_from_numeric(struct address buf[static 1], const char *name, int family)
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44 | {
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45 | return __lookup_ipliteral(buf, name, family);
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46 | }
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47 |
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48 | static int name_from_hosts(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
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49 | {
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50 | char line[512];
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51 | size_t l = strlen(name);
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52 | int cnt = 0, badfam = 0;
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53 | unsigned char _buf[1032];
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54 | FILE _f, *f = __fopen_rb_ca("/etc/hosts", &_f, _buf, sizeof _buf);
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55 | if (!f) switch (errno) {
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56 | case ENOENT:
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57 | case ENOTDIR:
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58 | case EACCES:
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59 | return 0;
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60 | default:
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61 | return EAI_SYSTEM;
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62 | }
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63 | while (fgets(line, sizeof line, f) && cnt < MAXADDRS) {
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64 | char *p, *z;
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65 |
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66 | if ((p=strchr(line, '#'))) *p++='\n', *p=0;
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67 | for(p=line+1; (p=strstr(p, name)) &&
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68 | (!isspace(p[-1]) || !isspace(p[l])); p++);
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69 | if (!p) continue;
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70 |
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71 | /* Isolate IP address to parse */
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72 | for (p=line; *p && !isspace(*p); p++);
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73 | *p++ = 0;
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74 | switch (name_from_numeric(buf+cnt, line, family)) {
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75 | case 1:
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76 | cnt++;
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77 | break;
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78 | case 0:
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79 | continue;
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80 | default:
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81 | badfam = EAI_NONAME;
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82 | continue;
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83 | }
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84 |
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85 | /* Extract first name as canonical name */
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86 | for (; *p && isspace(*p); p++);
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87 | for (z=p; *z && !isspace(*z); z++);
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88 | *z = 0;
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89 | if (is_valid_hostname(p)) memcpy(canon, p, z-p+1);
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90 | }
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91 | __fclose_ca(f);
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92 | return cnt ? cnt : badfam;
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93 | }
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94 |
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95 | struct dpc_ctx {
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96 | struct address *addrs;
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97 | char *canon;
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98 | int cnt;
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99 | };
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100 |
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101 | int __dns_parse(const unsigned char *, int, int (*)(void *, int, const void *, int, const void *), void *);
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102 | int __dn_expand(const unsigned char *, const unsigned char *, const unsigned char *, char *, int);
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103 | int __res_mkquery(int, const char *, int, int, const unsigned char *, int, const unsigned char*, unsigned char *, int);
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104 | int __res_msend_rc(int, const unsigned char *const *, const int *, unsigned char *const *, int *, int, const struct resolvconf *);
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105 |
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106 | #define RR_A 1
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107 | #define RR_CNAME 5
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108 | #define RR_AAAA 28
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109 |
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110 | static int dns_parse_callback(void *c, int rr, const void *data, int len, const void *packet)
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111 | {
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112 | char tmp[256];
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113 | struct dpc_ctx *ctx = c;
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114 | if (ctx->cnt >= MAXADDRS) return -1;
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115 | switch (rr) {
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116 | case RR_A:
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117 | if (len != 4) return -1;
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118 | ctx->addrs[ctx->cnt].family = AF_INET;
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119 | ctx->addrs[ctx->cnt].scopeid = 0;
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120 | memcpy(ctx->addrs[ctx->cnt++].addr, data, 4);
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121 | break;
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122 | case RR_AAAA:
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123 | if (len != 16) return -1;
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124 | ctx->addrs[ctx->cnt].family = AF_INET6;
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125 | ctx->addrs[ctx->cnt].scopeid = 0;
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126 | memcpy(ctx->addrs[ctx->cnt++].addr, data, 16);
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127 | break;
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128 | case RR_CNAME:
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129 | if (__dn_expand(packet, (const unsigned char *)packet + 512,
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130 | data, tmp, sizeof tmp) > 0 && is_valid_hostname(tmp))
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131 | strcpy(ctx->canon, tmp);
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132 | break;
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133 | }
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134 | return 0;
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135 | }
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136 |
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137 | static int name_from_dns(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, const struct resolvconf *conf)
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138 | {
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139 | unsigned char qbuf[2][280], abuf[2][512];
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140 | const unsigned char *qp[2] = { qbuf[0], qbuf[1] };
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141 | unsigned char *ap[2] = { abuf[0], abuf[1] };
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142 | int qlens[2], alens[2];
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143 | int i, nq = 0;
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144 | struct dpc_ctx ctx = { .addrs = buf, .canon = canon };
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145 | static const struct { int af; int rr; } afrr[2] = {
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146 | { .af = AF_INET6, .rr = RR_A },
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147 | { .af = AF_INET, .rr = RR_AAAA },
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148 | };
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149 |
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150 | for (i=0; i<2; i++) {
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151 | if (family != afrr[i].af) {
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152 | qlens[nq] = __res_mkquery(0, name, 1, afrr[i].rr,
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153 | 0, 0, 0, qbuf[nq], sizeof *qbuf);
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154 | if (qlens[nq] == -1)
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155 | return EAI_NONAME;
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156 | nq++;
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157 | }
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158 | }
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159 |
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160 | if (__res_msend_rc(nq, qp, qlens, ap, alens, sizeof *abuf, conf) < 0)
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161 | return EAI_SYSTEM;
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162 |
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163 | for (i=0; i<nq; i++)
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164 | __dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
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165 |
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166 | if (ctx.cnt) return ctx.cnt;
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167 | if (alens[0] < 4 || (abuf[0][3] & 15) == 2) return EAI_AGAIN;
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168 | if ((abuf[0][3] & 15) == 0) return EAI_NONAME;
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169 | if ((abuf[0][3] & 15) == 3) return 0;
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170 | return EAI_FAIL;
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171 | }
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172 |
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173 | static int name_from_dns_search(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family)
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174 | {
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175 | char search[256];
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176 | struct resolvconf conf;
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177 | size_t l, dots;
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178 | char *p, *z;
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179 |
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180 | if (__get_resolv_conf(&conf, search, sizeof search) < 0) return -1;
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181 |
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182 | /* Count dots, suppress search when >=ndots or name ends in
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183 | * a dot, which is an explicit request for global scope. */
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184 | for (dots=l=0; name[l]; l++) if (name[l]=='.') dots++;
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185 | if (dots >= conf.ndots || name[l-1]=='.') *search = 0;
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186 |
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187 | /* This can never happen; the caller already checked length. */
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188 | if (l >= 256) return EAI_NONAME;
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189 |
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190 | /* Name with search domain appended is setup in canon[]. This both
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191 | * provides the desired default canonical name (if the requested
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192 | * name is not a CNAME record) and serves as a buffer for passing
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193 | * the full requested name to name_from_dns. */
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194 | memcpy(canon, name, l);
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195 | canon[l] = '.';
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196 |
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197 | for (p=search; *p; p=z) {
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198 | for (; isspace(*p); p++);
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199 | for (z=p; *z && !isspace(*z); z++);
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200 | if (z==p) break;
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201 | if (z-p < 256 - l - 1) {
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202 | memcpy(canon+l+1, p, z-p);
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203 | canon[z-p+1+l] = 0;
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204 | int cnt = name_from_dns(buf, canon, canon, family, &conf);
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205 | if (cnt) return cnt;
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206 | }
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207 | }
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208 |
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209 | canon[l] = 0;
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210 | return name_from_dns(buf, canon, name, family, &conf);
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211 | }
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212 |
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213 | static const struct policy {
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214 | unsigned char addr[16];
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215 | unsigned char len, mask;
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216 | unsigned char prec, label;
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217 | } defpolicy[] = {
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218 | { "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\1", 15, 0xff, 50, 0 },
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219 | { "\0\0\0\0\0\0\0\0\0\0\xff\xff", 11, 0xff, 35, 4 },
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220 | { "\x20\2", 1, 0xff, 30, 2 },
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221 | { "\x20\1", 3, 0xff, 5, 5 },
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222 | { "\xfc", 0, 0xfe, 3, 13 },
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223 | #if 0
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224 | /* These are deprecated and/or returned to the address
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225 | * pool, so despite the RFC, treating them as special
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226 | * is probably wrong. */
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227 | { "", 11, 0xff, 1, 3 },
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228 | { "\xfe\xc0", 1, 0xc0, 1, 11 },
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229 | { "\x3f\xfe", 1, 0xff, 1, 12 },
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230 | #endif
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231 | /* Last rule must match all addresses to stop loop. */
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232 | { "", 0, 0, 40, 1 },
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233 | };
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234 |
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235 | static const struct policy *policyof(const struct in6_addr *a)
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236 | {
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237 | int i;
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238 | for (i=0; ; i++) {
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239 | if (memcmp(a->s6_addr, defpolicy[i].addr, defpolicy[i].len))
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240 | continue;
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241 | if ((a->s6_addr[defpolicy[i].len] & defpolicy[i].mask)
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242 | != defpolicy[i].addr[defpolicy[i].len])
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243 | continue;
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244 | return defpolicy+i;
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245 | }
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246 | }
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247 |
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248 | static int labelof(const struct in6_addr *a)
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249 | {
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250 | return policyof(a)->label;
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251 | }
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252 |
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253 | static int scopeof(const struct in6_addr *a)
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254 | {
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255 | if (IN6_IS_ADDR_MULTICAST(a)) return a->s6_addr[1] & 15;
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256 | if (IN6_IS_ADDR_LINKLOCAL(a)) return 2;
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257 | if (IN6_IS_ADDR_LOOPBACK(a)) return 2;
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258 | if (IN6_IS_ADDR_SITELOCAL(a)) return 5;
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259 | return 14;
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260 | }
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261 |
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262 | static int prefixmatch(const struct in6_addr *s, const struct in6_addr *d)
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263 | {
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264 | /* FIXME: The common prefix length should be limited to no greater
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265 | * than the nominal length of the prefix portion of the source
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266 | * address. However the definition of the source prefix length is
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267 | * not clear and thus this limiting is not yet implemented. */
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268 | unsigned i;
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269 | for (i=0; i<128 && !((s->s6_addr[i/8]^d->s6_addr[i/8])&(128>>(i%8))); i++);
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270 | return i;
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271 | }
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272 |
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273 | #define DAS_USABLE 0x40000000
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274 | #define DAS_MATCHINGSCOPE 0x20000000
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275 | #define DAS_MATCHINGLABEL 0x10000000
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276 | #define DAS_PREC_SHIFT 20
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277 | #define DAS_SCOPE_SHIFT 16
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278 | #define DAS_PREFIX_SHIFT 8
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279 | #define DAS_ORDER_SHIFT 0
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280 |
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281 | static int addrcmp(const void *_a, const void *_b)
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282 | {
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283 | const struct address *a = _a, *b = _b;
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284 | return b->sortkey - a->sortkey;
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285 | }
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286 |
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287 | int __lookup_name(struct address buf[static MAXADDRS], char canon[static 256], const char *name, int family, int flags)
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288 | {
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289 | int cnt = 0, i, j;
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290 |
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291 | *canon = 0;
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292 | if (name) {
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293 | /* reject empty name and check len so it fits into temp bufs */
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294 | size_t l = strnlen(name, 255);
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295 | if (l-1 >= 254)
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296 | return EAI_NONAME;
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297 | memcpy(canon, name, l+1);
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298 | }
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299 |
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300 | /* Procedurally, a request for v6 addresses with the v4-mapped
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301 | * flag set is like a request for unspecified family, followed
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302 | * by filtering of the results. */
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303 | if (flags & AI_V4MAPPED) {
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304 | if (family == AF_INET6) family = AF_UNSPEC;
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305 | else flags -= AI_V4MAPPED;
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306 | }
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307 |
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308 | /* Try each backend until there's at least one result. */
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309 | cnt = name_from_null(buf, name, family, flags);
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310 | if (!cnt) cnt = name_from_numeric(buf, name, family);
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311 | if (!cnt && !(flags & AI_NUMERICHOST)) {
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312 | cnt = name_from_hosts(buf, canon, name, family);
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313 | if (!cnt) cnt = name_from_dns_search(buf, canon, name, family);
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314 | }
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315 | if (cnt<=0) return cnt ? cnt : EAI_NONAME;
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316 |
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317 | /* Filter/transform results for v4-mapped lookup, if requested. */
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318 | if (flags & AI_V4MAPPED) {
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319 | if (!(flags & AI_ALL)) {
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320 | /* If any v6 results exist, remove v4 results. */
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321 | for (i=0; i<cnt && buf[i].family != AF_INET6; i++);
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322 | if (i<cnt) {
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323 | for (j=0; i<cnt; i++) {
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324 | if (buf[i].family == AF_INET6)
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325 | buf[j++] = buf[i];
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326 | }
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327 | cnt = i = j;
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328 | }
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329 | }
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330 | /* Translate any remaining v4 results to v6 */
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331 | for (i=0; i<cnt; i++) {
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332 | if (buf[i].family != AF_INET) continue;
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333 | memcpy(buf[i].addr+12, buf[i].addr, 4);
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334 | memcpy(buf[i].addr, "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
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335 | buf[i].family = AF_INET6;
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336 | }
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337 | }
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338 |
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339 | /* No further processing is needed if there are fewer than 2
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340 | * results or if there are only IPv4 results. */
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341 | if (cnt<2 || family==AF_INET) return cnt;
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342 | for (i=0; i<cnt; i++) if (buf[i].family != AF_INET) break;
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343 | if (i==cnt) return cnt;
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344 |
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345 | int cs;
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346 | pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
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347 |
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348 | /* The following implements a subset of RFC 3484/6724 destination
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349 | * address selection by generating a single 31-bit sort key for
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350 | * each address. Rules 3, 4, and 7 are omitted for having
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351 | * excessive runtime and code size cost and dubious benefit.
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352 | * So far the label/precedence table cannot be customized. */
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353 | for (i=0; i<cnt; i++) {
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354 | int key = 0;
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355 | struct sockaddr_in6 sa, da = {
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356 | .sin6_family = AF_INET6,
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357 | .sin6_scope_id = buf[i].scopeid,
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358 | .sin6_port = 65535
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359 | };
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360 | if (buf[i].family == AF_INET6) {
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361 | memcpy(da.sin6_addr.s6_addr, buf[i].addr, 16);
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362 | } else {
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363 | memcpy(da.sin6_addr.s6_addr,
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364 | "\0\0\0\0\0\0\0\0\0\0\xff\xff", 12);
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365 | memcpy(da.sin6_addr.s6_addr+12, buf[i].addr, 4);
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366 | }
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367 | const struct policy *dpolicy = policyof(&da.sin6_addr);
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368 | int dscope = scopeof(&da.sin6_addr);
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369 | int dlabel = dpolicy->label;
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370 | int dprec = dpolicy->prec;
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371 | int prefixlen = 0;
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372 | int fd = socket(AF_INET6, SOCK_DGRAM|SOCK_CLOEXEC, IPPROTO_UDP);
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373 | if (fd >= 0) {
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374 | if (!connect(fd, (void *)&da, sizeof da)) {
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375 | key |= DAS_USABLE;
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376 | if (!getsockname(fd, (void *)&sa,
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377 | &(socklen_t){sizeof sa})) {
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378 | if (dscope == scopeof(&sa.sin6_addr))
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379 | key |= DAS_MATCHINGSCOPE;
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380 | if (dlabel == labelof(&sa.sin6_addr))
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381 | key |= DAS_MATCHINGLABEL;
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382 | prefixlen = prefixmatch(&sa.sin6_addr,
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383 | &da.sin6_addr);
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384 | }
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385 | }
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386 | close(fd);
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387 | }
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388 | key |= dprec << DAS_PREC_SHIFT;
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389 | key |= (15-dscope) << DAS_SCOPE_SHIFT;
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390 | key |= prefixlen << DAS_PREFIX_SHIFT;
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391 | key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
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392 | buf[i].sortkey = key;
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393 | }
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394 | qsort(buf, cnt, sizeof *buf, addrcmp);
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395 |
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396 | pthread_setcancelstate(cs, 0);
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397 |
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398 | return cnt;
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399 | }
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