1/* Copyright (C) 1999-2021 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Andreas Jaeger <aj@suse.de>.
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 "ifreq.h"
20
21
22void
23__ifreq (struct ifreq **ifreqs, int *num_ifs, int sockfd)
24{
25 int fd = sockfd;
26 struct ifconf ifc;
27 int rq_len;
28 int nifs;
29# define RQ_IFS 4
30
31 if (fd < 0)
32 fd = __opensock ();
33 if (fd < 0)
34 {
35 *num_ifs = 0;
36 *ifreqs = NULL;
37 return;
38 }
39
40 ifc.ifc_buf = NULL;
41
42 /* We may be able to get the needed buffer size directly, rather than
43 guessing. */
44 ifc.ifc_buf = NULL;
45 ifc.ifc_len = 0;
46 if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 || ifc.ifc_len == 0)
47 rq_len = RQ_IFS * sizeof (struct ifreq);
48 else
49 rq_len = ifc.ifc_len;
50
51 /* Read all the interfaces out of the kernel. */
52 ifc.ifc_len = rq_len;
53 void *newp = realloc (ifc.ifc_buf, ifc.ifc_len);
54 if (newp == NULL
55 || (ifc.ifc_buf = newp, __ioctl (fd, SIOCGIFCONF, &ifc)) < 0)
56 {
57 free (ifc.ifc_buf);
58
59 if (fd != sockfd)
60 __close (fd);
61
62 *num_ifs = 0;
63 *ifreqs = NULL;
64 return;
65 }
66
67 nifs = ifc.ifc_len / sizeof (struct ifreq);
68
69 if (fd != sockfd)
70 __close (fd);
71
72 *num_ifs = nifs;
73 *ifreqs = realloc (ifc.ifc_buf, nifs * sizeof (struct ifreq));
74}
75