1/* Copyright (C) 1999-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include "ifreq.h"
19
20
21void
22__ifreq (struct ifreq **ifreqs, int *num_ifs, int sockfd)
23{
24 int fd = sockfd;
25 struct ifconf ifc;
26 int rq_len;
27 int nifs;
28# define RQ_IFS 4
29
30 if (fd < 0)
31 fd = __opensock ();
32 if (fd < 0)
33 {
34 *num_ifs = 0;
35 *ifreqs = NULL;
36 return;
37 }
38
39 ifc.ifc_buf = NULL;
40
41 /* We may be able to get the needed buffer size directly, rather than
42 guessing. */
43 ifc.ifc_buf = NULL;
44 ifc.ifc_len = 0;
45 if (__ioctl (fd, SIOCGIFCONF, &ifc) < 0 || ifc.ifc_len == 0)
46 rq_len = RQ_IFS * sizeof (struct ifreq);
47 else
48 rq_len = ifc.ifc_len;
49
50 /* Read all the interfaces out of the kernel. */
51 ifc.ifc_len = rq_len;
52 void *newp = realloc (ifc.ifc_buf, ifc.ifc_len);
53 if (newp == NULL
54 || (ifc.ifc_buf = newp, __ioctl (fd, SIOCGIFCONF, &ifc)) < 0)
55 {
56 free (ifc.ifc_buf);
57
58 if (fd != sockfd)
59 __close (fd);
60
61 *num_ifs = 0;
62 *ifreqs = NULL;
63 return;
64 }
65
66 nifs = ifc.ifc_len / sizeof (struct ifreq);
67
68 if (fd != sockfd)
69 __close (fd);
70
71 *num_ifs = nifs;
72 *ifreqs = realloc (ifc.ifc_buf, nifs * sizeof (struct ifreq));
73}
74