[331] | 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 | }
|
---|
| 388 | key |= dprec << DAS_PREC_SHIFT;
|
---|
| 389 | key |= (15-dscope) << DAS_SCOPE_SHIFT;
|
---|
| 390 | key |= prefixlen << DAS_PREFIX_SHIFT;
|
---|
| 391 | key |= (MAXADDRS-i) << DAS_ORDER_SHIFT;
|
---|
| 392 | buf[i].sortkey = key;
|
---|
| 393 | }
|
---|
| 394 | qsort(buf, cnt, sizeof *buf, addrcmp);
|
---|
| 395 |
|
---|
| 396 | pthread_setcancelstate(cs, 0);
|
---|
| 397 |
|
---|
| 398 | return cnt;
|
---|
| 399 | }
|
---|