1 /* getifaddrs -- get names and addresses of all network interfaces
2 Copyright (C) 2002-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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 <ifaddrs.h>
20 #include <net/if.h>
21 #include <sys/socket.h>
22 #include <sys/ioctl.h>
23 #include <unistd.h>
24 #include <stdlib.h>
25 #include <string.h>
26 #include <errno.h>
27 #include <netinet/in.h>
28
29 #include "ifreq.h"
30
31 /* Create a linked list of `struct ifaddrs' structures, one for each
32 network interface on the host machine. If successful, store the
33 list in *IFAP and return 0. On errors, return -1 and set `errno'. */
34 int
35 __getifaddrs (struct ifaddrs **ifap)
36 {
37 /* This implementation handles only IPv4 interfaces.
38 The various ioctls below will only work on an AF_INET socket.
39 Some different mechanism entirely must be used for IPv6. */
40 int fd = __socket (AF_INET, SOCK_DGRAM, 0);
41 struct ifreq *ifreqs;
42 int nifs;
43
44 if (fd < 0)
45 return -1;
46
47 __ifreq (&ifreqs, &nifs, fd);
48 if (ifreqs == NULL) /* XXX doesn't distinguish error vs none */
49 {
50 __close (fd);
51 return -1;
52 }
53
54 /* Now we have the list of interfaces and each one's address.
55 Put it into the expected format and fill in the remaining details. */
56 if (nifs == 0)
57 *ifap = NULL;
58 else
59 {
60 struct
61 {
62 struct ifaddrs ia;
63 struct sockaddr addr, netmask, broadaddr;
64 char name[IF_NAMESIZE];
65 } *storage;
66 struct ifreq *ifr;
67 int i;
68
69 storage = malloc (nifs * sizeof storage[0]);
70 if (storage == NULL)
71 {
72 __close (fd);
73 __if_freereq (ifreqs, nifs);
74 return -1;
75 }
76
77 i = 0;
78 ifr = ifreqs;
79 do
80 {
81 /* Fill in pointers to the storage we've already allocated. */
82 storage[i].ia.ifa_next = &storage[i + 1].ia;
83 storage[i].ia.ifa_addr = &storage[i].addr;
84
85 /* Now copy the information we already have from SIOCGIFCONF. */
86 storage[i].ia.ifa_name = strncpy (storage[i].name, ifr->ifr_name,
87 sizeof storage[i].name);
88 storage[i].addr = ifr->ifr_addr;
89
90 /* The SIOCGIFCONF call filled in only the name and address.
91 Now we must also ask for the other information we need. */
92
93 if (__ioctl (fd, SIOCGIFFLAGS, ifr) < 0)
94 break;
95 storage[i].ia.ifa_flags = ifr->ifr_flags;
96
97 ifr->ifr_addr = storage[i].addr;
98
99 if (__ioctl (fd, SIOCGIFNETMASK, ifr) < 0)
100 storage[i].ia.ifa_netmask = NULL;
101 else
102 {
103 storage[i].ia.ifa_netmask = &storage[i].netmask;
104 storage[i].netmask = ifr->ifr_netmask;
105 }
106
107 if (ifr->ifr_flags & IFF_BROADCAST)
108 {
109 ifr->ifr_addr = storage[i].addr;
110 if (__ioctl (fd, SIOCGIFBRDADDR, ifr) < 0)
111 storage[i].ia.ifa_broadaddr = NULL;
112 {
113 storage[i].ia.ifa_broadaddr = &storage[i].broadaddr;
114 storage[i].broadaddr = ifr->ifr_broadaddr;
115 }
116 }
117 else if (ifr->ifr_flags & IFF_POINTOPOINT)
118 {
119 ifr->ifr_addr = storage[i].addr;
120 if (__ioctl (fd, SIOCGIFDSTADDR, ifr) < 0)
121 storage[i].ia.ifa_broadaddr = NULL;
122 else
123 {
124 storage[i].ia.ifa_broadaddr = &storage[i].broadaddr;
125 storage[i].broadaddr = ifr->ifr_dstaddr;
126 }
127 }
128 else
129 storage[i].ia.ifa_broadaddr = NULL;
130
131 storage[i].ia.ifa_data = NULL; /* Nothing here for now. */
132
133 ifr = __if_nextreq (ifr);
134 } while (++i < nifs);
135 if (i < nifs) /* Broke out early on error. */
136 {
137 __close (fd);
138 free (storage);
139 __if_freereq (ifreqs, nifs);
140 return -1;
141 }
142
143 storage[i - 1].ia.ifa_next = NULL;
144
145 *ifap = &storage[0].ia;
146
147 __close (fd);
148 __if_freereq (ifreqs, nifs);
149 }
150
151 return 0;
152 }
153 weak_alias (__getifaddrs, getifaddrs)
154 libc_hidden_def (__getifaddrs)
155 #ifndef getifaddrs
156 libc_hidden_weak (getifaddrs)
157 #endif
158
159 void
160 __freeifaddrs (struct ifaddrs *ifa)
161 {
162 free (ifa);
163 }
164 weak_alias (__freeifaddrs, freeifaddrs)
165 libc_hidden_def (__freeifaddrs)
166 libc_hidden_weak (freeifaddrs)