1#define _GNU_SOURCE
2
3#include <sys/socket.h>
4#include <netdb.h>
5#include <string.h>
6#include <netinet/in.h>
7#include <errno.h>
8#include <inttypes.h>
9
10int gethostbyaddr_r(const void *a, socklen_t l, int af,
11 struct hostent *h, char *buf, size_t buflen,
12 struct hostent **res, int *err)
13{
14 union {
15 struct sockaddr_in sin;
16 struct sockaddr_in6 sin6;
17 } sa = { .sin.sin_family = af };
18 socklen_t sl = af==AF_INET6 ? sizeof sa.sin6 : sizeof sa.sin;
19 int i;
20
21 *res = 0;
22
23 /* Load address argument into sockaddr structure */
24 if (af==AF_INET6 && l==16) memcpy(&sa.sin6.sin6_addr, a, 16);
25 else if (af==AF_INET && l==4) memcpy(&sa.sin.sin_addr, a, 4);
26 else {
27 *err = NO_RECOVERY;
28 return EINVAL;
29 }
30
31 /* Align buffer and check for space for pointers and ip address */
32 i = (uintptr_t)buf & sizeof(char *)-1;
33 if (!i) i = sizeof(char *);
34 if (buflen <= 5*sizeof(char *)-i + l) return ERANGE;
35 buf += sizeof(char *)-i;
36 buflen -= 5*sizeof(char *)-i + l;
37
38 h->h_addr_list = (void *)buf;
39 buf += 2*sizeof(char *);
40 h->h_aliases = (void *)buf;
41 buf += 2*sizeof(char *);
42
43 h->h_addr_list[0] = buf;
44 memcpy(h->h_addr_list[0], a, l);
45 buf += l;
46 h->h_addr_list[1] = 0;
47 h->h_aliases[0] = buf;
48 h->h_aliases[1] = 0;
49
50 switch (getnameinfo((void *)&sa, sl, buf, buflen, 0, 0, 0)) {
51 case EAI_AGAIN:
52 *err = TRY_AGAIN;
53 return EAGAIN;
54 case EAI_OVERFLOW:
55 return ERANGE;
56 default:
57 case EAI_FAIL:
58 *err = NO_RECOVERY;
59 return EBADMSG;
60 case EAI_SYSTEM:
61 *err = NO_RECOVERY;
62 return errno;
63 case 0:
64 break;
65 }
66
67 h->h_addrtype = af;
68 h->h_length = l;
69 h->h_name = h->h_aliases[0];
70 *res = h;
71 return 0;
72}