1#define _GNU_SOURCE
2#include <sys/socket.h>
3#include <netinet/in.h>
4#include <netdb.h>
5#include <inttypes.h>
6#include <errno.h>
7#include <string.h>
8#include <stdlib.h>
9
10int getservbyport_r(int port, const char *prots,
11 struct servent *se, char *buf, size_t buflen, struct servent **res)
12{
13 int i;
14 struct sockaddr_in sin = {
15 .sin_family = AF_INET,
16 .sin_port = port,
17 };
18
19 if (!prots) {
20 int r = getservbyport_r(port, "tcp", se, buf, buflen, res);
21 if (r) r = getservbyport_r(port, "udp", se, buf, buflen, res);
22 return r;
23 }
24 *res = 0;
25
26 /* Align buffer */
27 i = (uintptr_t)buf & sizeof(char *)-1;
28 if (!i) i = sizeof(char *);
29 if (buflen <= 3*sizeof(char *)-i)
30 return ERANGE;
31 buf += sizeof(char *)-i;
32 buflen -= sizeof(char *)-i;
33
34 if (strcmp(prots, "tcp") && strcmp(prots, "udp")) return EINVAL;
35
36 se->s_port = port;
37 se->s_proto = (char *)prots;
38 se->s_aliases = (void *)buf;
39 buf += 2*sizeof(char *);
40 buflen -= 2*sizeof(char *);
41 se->s_aliases[1] = 0;
42 se->s_aliases[0] = se->s_name = buf;
43
44 switch (getnameinfo((void *)&sin, sizeof sin, 0, 0, buf, buflen,
45 strcmp(prots, "udp") ? 0 : NI_DGRAM)) {
46 case EAI_MEMORY:
47 case EAI_SYSTEM:
48 return ENOMEM;
49 case EAI_OVERFLOW:
50 return ERANGE;
51 default:
52 return ENOENT;
53 case 0:
54 break;
55 }
56
57 /* A numeric port string is not a service record. */
58 if (strtol(buf, 0, 10)==ntohs(port)) return ENOENT;
59
60 *res = se;
61 return 0;
62}