1 /* Determine whether interfaces use native transport. Linux version.
2 Copyright (C) 2007-2023 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 <assert.h>
20 #include <errno.h>
21 #include <ifaddrs.h>
22 #include <stddef.h>
23 #include <stdint.h>
24 #include <stdlib.h>
25 #include <string.h>
26 #include <time.h>
27 #include <unistd.h>
28 #include <net/if.h>
29 #include <net/if_arp.h>
30 #include <sys/ioctl.h>
31
32 #include <asm/types.h>
33 #include <linux/netlink.h>
34 #include <linux/rtnetlink.h>
35
36 #include <not-cancel.h>
37
38 #include "netlinkaccess.h"
39
40 void
41 __check_native (uint32_t a1_index, int *a1_native,
42 uint32_t a2_index, int *a2_native)
43 {
44 int fd = __socket (PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
45
46 struct sockaddr_nl nladdr;
47 memset (&nladdr, '\0', sizeof (nladdr));
48 nladdr.nl_family = AF_NETLINK;
49
50 socklen_t addr_len = sizeof (nladdr);
51
52 if (fd < 0)
53 return;
54
55 /* Netlink requires that user buffer needs to be either 8kb or page size
56 (whichever is bigger), however this has been changed over time and now
57 8Kb is sufficient (check NLMSG_DEFAULT_SIZE on Linux
58 linux/include/linux/netlink.h). */
59 const size_t buf_size = 8192;
60 char *buf = malloc (buf_size);
61
62 if (buf == NULL)
63 goto out;
64
65 if (__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) != 0
66 || __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) != 0)
67 goto out;
68
69 pid_t pid = nladdr.nl_pid;
70 struct req
71 {
72 struct nlmsghdr nlh;
73 struct rtgenmsg g;
74 /* struct rtgenmsg consists of a single byte. This means there
75 are three bytes of padding included in the REQ definition.
76 We make them explicit here. */
77 char pad[3];
78 } req;
79
80 req.nlh.nlmsg_len = sizeof (req);
81 req.nlh.nlmsg_type = RTM_GETLINK;
82 req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
83 req.nlh.nlmsg_pid = 0;
84 req.nlh.nlmsg_seq = time_now ();
85 req.g.rtgen_family = AF_UNSPEC;
86
87 assert (sizeof (req) - offsetof (struct req, pad) == 3);
88 memset (req.pad, '\0', sizeof (req.pad));
89
90 memset (&nladdr, '\0', sizeof (nladdr));
91 nladdr.nl_family = AF_NETLINK;
92
93 struct iovec iov = { buf, buf_size };
94
95 if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
96 (struct sockaddr *) &nladdr,
97 sizeof (nladdr))) < 0)
98 goto out;
99
100 bool done = false;
101 do
102 {
103 struct msghdr msg =
104 {
105 .msg_name = (void *) &nladdr,
106 .msg_namelen = sizeof (nladdr),
107 .msg_iov = &iov,
108 .msg_iovlen = 1,
109 .msg_control = NULL,
110 .msg_controllen = 0,
111 .msg_flags = 0
112 };
113
114 ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
115 __netlink_assert_response (fd, read_len);
116 if (read_len < 0)
117 goto out;
118
119 if (msg.msg_flags & MSG_TRUNC)
120 goto out;
121
122 struct nlmsghdr *nlmh;
123 for (nlmh = (struct nlmsghdr *) buf;
124 NLMSG_OK (nlmh, (size_t) read_len);
125 nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
126 {
127 if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
128 || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
129 continue;
130
131 if (nlmh->nlmsg_type == RTM_NEWLINK)
132 {
133 struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlmh);
134 int native = (ifim->ifi_type != ARPHRD_TUNNEL6
135 && ifim->ifi_type != ARPHRD_TUNNEL
136 && ifim->ifi_type != ARPHRD_SIT);
137
138 if (a1_index == ifim->ifi_index)
139 {
140 *a1_native = native;
141 a1_index = 0xffffffffu;
142 }
143 if (a2_index == ifim->ifi_index)
144 {
145 *a2_native = native;
146 a2_index = 0xffffffffu;
147 }
148
149 if (a1_index == 0xffffffffu
150 && a2_index == 0xffffffffu)
151 goto out;
152 }
153 else if (nlmh->nlmsg_type == NLMSG_DONE)
154 /* We found the end, leave the loop. */
155 done = true;
156 }
157 }
158 while (! done);
159
160 out:
161 __close_nocancel_nostatus (fd);
162 free (buf);
163 }