third_party/ulib/musl/src/network/gethostbyaddr_r.c

#define _GNU_SOURCE

#include <errno.h>
#include <inttypes.h>
#include <netdb.h>
#include <netinet/in.h>
#include <string.h>
#include <sys/socket.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_length = l;
    h->h_name = h->h_aliases[0];
    *res = h;
    return 0;
}