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#define _GNU_SOURCE
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
#include <netinet/in.h>
#include <errno.h>
#include <inttypes.h>
int gethostbyaddr_r(const void *a, socklen_t l, int af,
struct hostent *h, char *buf, size_t buflen,
struct hostent **res, int *err)
{
union {
struct sockaddr_in sin;
struct sockaddr_in6 sin6;
} sa = { .sin.sin_family = af };
socklen_t sl = af==AF_INET6 ? sizeof sa.sin6 : sizeof sa.sin;
int i;
*res = 0;
/* Load address argument into sockaddr structure */
if (af==AF_INET6 && l==16) memcpy(&sa.sin6.sin6_addr, a, 16);
else if (af==AF_INET && l==4) memcpy(&sa.sin.sin_addr, a, 4);
else {
*err = NO_RECOVERY;
return EINVAL;
}
/* Align buffer and check for space for pointers and ip address */
i = (uintptr_t)buf & sizeof(char *)-1;
if (!i) i = sizeof(char *);
if (buflen <= 5*sizeof(char *)-i + l) return ERANGE;
buf += sizeof(char *)-i;
buflen -= 5*sizeof(char *)-i + l;
h->h_addr_list = (void *)buf;
buf += 2*sizeof(char *);
h->h_aliases = (void *)buf;
buf += 2*sizeof(char *);
h->h_addr_list[0] = buf;
memcpy(h->h_addr_list[0], a, l);
buf += l;
h->h_addr_list[1] = 0;
h->h_aliases[0] = buf;
h->h_aliases[1] = 0;
switch (getnameinfo((void *)&sa, sl, buf, buflen, 0, 0, 0)) {
case EAI_AGAIN:
*err = TRY_AGAIN;
return EAGAIN;
case EAI_OVERFLOW:
return ERANGE;
default:
case EAI_MEMORY:
case EAI_SYSTEM:
case EAI_FAIL:
*err = NO_RECOVERY;
return errno;
case 0:
break;
}
h->h_addrtype = af;
h->h_name = h->h_aliases[0];
*res = h;
return 0;
}
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