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
9int getservbyport_r(int port, const char *prots,
10	struct servent *se, char *buf, size_t buflen, struct servent **res)
11{
12	int i;
13	struct sockaddr_in sin = {
14		.sin_family = AF_INET,
15		.sin_port = port,
16	};
17
18	if (!prots) {
19		int r = getservbyport_r(port, "tcp", se, buf, buflen, res);
20		if (r) r = getservbyport_r(port, "udp", se, buf, buflen, res);
21		return r;
22	}
23	*res = 0;
24
25	/* Align buffer */
26	i = (uintptr_t)buf & sizeof(char *)-1;
27	if (!i) i = sizeof(char *);
28	if (buflen < 3*sizeof(char *)-i)
29		return ERANGE;
30	buf += sizeof(char *)-i;
31	buflen -= sizeof(char *)-i;
32
33	if (strcmp(prots, "tcp") && strcmp(prots, "udp")) return EINVAL;
34
35	se->s_port = port;
36	se->s_proto = (char *)prots;
37	se->s_aliases = (void *)buf;
38	buf += 2*sizeof(char *);
39	buflen -= 2*sizeof(char *);
40	se->s_aliases[1] = 0;
41	se->s_aliases[0] = se->s_name = buf;
42
43	switch (getnameinfo((void *)&sin, sizeof sin, 0, 0, buf, buflen,
44		strcmp(prots, "udp") ? 0 : NI_DGRAM)) {
45	case EAI_MEMORY:
46	case EAI_SYSTEM:
47		return ENOMEM;
48	default:
49		return ENOENT;
50	case 0:
51		break;
52	}
53
54	*res = se;
55	return 0;
56}
57