1/* Copyright (C) 1996-2020 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <errno.h>
20#include <netinet/ether.h>
21#include <netinet/if_ether.h>
22#include <string.h>
23
24#include <nss/nsswitch.h>
25
26
27/* Type of the lookup function we need here. */
28typedef int (*lookup_function) (const struct ether_addr *, struct etherent *,
29 char *, size_t, int *);
30
31int
32ether_ntohost (char *hostname, const struct ether_addr *addr)
33{
34 static service_user *startp;
35 static lookup_function start_fct;
36 service_user *nip;
37 union
38 {
39 lookup_function f;
40 void *ptr;
41 } fct;
42 int no_more;
43 enum nss_status status = NSS_STATUS_UNAVAIL;
44 struct etherent etherent;
45
46 if (startp == NULL)
47 {
48 no_more = __nss_ethers_lookup2 (&nip, "getntohost_r", NULL, &fct.ptr);
49 if (no_more)
50 startp = (service_user *) -1;
51 else
52 {
53 startp = nip;
54 start_fct = fct.f;
55 }
56 }
57 else
58 {
59 fct.f = start_fct;
60 no_more = (nip = startp) == (service_user *) -1;
61 }
62
63 while (no_more == 0)
64 {
65 char buffer[1024];
66
67 status = (*fct.f) (addr, &etherent, buffer, sizeof buffer, &errno);
68
69 no_more = __nss_next2 (&nip, "getntohost_r", NULL, &fct.ptr, status, 0);
70 }
71
72 if (status == NSS_STATUS_SUCCESS)
73 /* XXX This is a potential cause of trouble because the size of
74 the HOSTNAME buffer is not known but the interface does not
75 provide this information. */
76 strcpy (hostname, etherent.e_name);
77
78 return status == NSS_STATUS_SUCCESS ? 0 : -1;
79}
80