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
gethostbyaddr_r(const void * a,socklen_t l,int af,struct hostent * h,char * buf,size_t buflen,struct hostent ** res,int * err)10 int 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_MEMORY:
58 case EAI_SYSTEM:
59 case EAI_FAIL:
60 *err = NO_RECOVERY;
61 return errno;
62 case 0:
63 break;
64 }
65
66 h->h_addrtype = af;
67 h->h_length = l;
68 h->h_name = h->h_aliases[0];
69 *res = h;
70 return 0;
71 }
72