1 | #define _GNU_SOURCE
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2 | #include <sys/socket.h>
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3 | #include <netinet/in.h>
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4 | #include <netdb.h>
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5 | #include <inttypes.h>
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6 | #include <errno.h>
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7 | #include <string.h>
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8 | #include <stdlib.h>
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9 |
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10 | int getservbyport_r(int port, const char *prots,
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11 | struct servent *se, char *buf, size_t buflen, struct servent **res)
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12 | {
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13 | int i;
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14 | struct sockaddr_in sin = {
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15 | .sin_family = AF_INET,
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16 | .sin_port = port,
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17 | };
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18 |
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19 | if (!prots) {
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20 | int r = getservbyport_r(port, "tcp", se, buf, buflen, res);
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21 | if (r) r = getservbyport_r(port, "udp", se, buf, buflen, res);
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22 | return r;
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23 | }
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24 | *res = 0;
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25 |
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26 | /* Align buffer */
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27 | i = (uintptr_t)buf & sizeof(char *)-1;
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28 | if (!i) i = sizeof(char *);
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29 | if (buflen < 3*sizeof(char *)-i)
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30 | return ERANGE;
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31 | buf += sizeof(char *)-i;
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32 | buflen -= sizeof(char *)-i;
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33 |
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34 | if (strcmp(prots, "tcp") && strcmp(prots, "udp")) return EINVAL;
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35 |
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36 | se->s_port = port;
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37 | se->s_proto = (char *)prots;
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38 | se->s_aliases = (void *)buf;
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39 | buf += 2*sizeof(char *);
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40 | buflen -= 2*sizeof(char *);
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41 | se->s_aliases[1] = 0;
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42 | se->s_aliases[0] = se->s_name = buf;
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43 |
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44 | switch (getnameinfo((void *)&sin, sizeof sin, 0, 0, buf, buflen,
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45 | strcmp(prots, "udp") ? 0 : NI_DGRAM)) {
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46 | case EAI_MEMORY:
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47 | case EAI_SYSTEM:
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48 | return ENOMEM;
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49 | default:
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50 | return ENOENT;
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51 | case 0:
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52 | break;
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53 | }
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54 |
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55 | /* A numeric port string is not a service record. */
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56 | if (strtol(buf, 0, 10)==ntohs(port)) return ENOENT;
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57 |
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58 | *res = se;
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59 | return 0;
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60 | }
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