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
40void
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 bool use_malloc = false;
52
53 if (fd < 0)
54 return;
55
56 if (__bind (fd, (struct sockaddr *) &nladdr, sizeof (nladdr)) != 0
57 || __getsockname (fd, (struct sockaddr *) &nladdr, &addr_len) != 0)
58 goto out;
59
60 pid_t pid = nladdr.nl_pid;
61 struct req
62 {
63 struct nlmsghdr nlh;
64 struct rtgenmsg g;
65 /* struct rtgenmsg consists of a single byte. This means there
66 are three bytes of padding included in the REQ definition.
67 We make them explicit here. */
68 char pad[3];
69 } req;
70
71 req.nlh.nlmsg_len = sizeof (req);
72 req.nlh.nlmsg_type = RTM_GETLINK;
73 req.nlh.nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
74 req.nlh.nlmsg_pid = 0;
75 req.nlh.nlmsg_seq = time_now ();
76 req.g.rtgen_family = AF_UNSPEC;
77
78 assert (sizeof (req) - offsetof (struct req, pad) == 3);
79 memset (req.pad, '\0', sizeof (req.pad));
80
81 memset (&nladdr, '\0', sizeof (nladdr));
82 nladdr.nl_family = AF_NETLINK;
83
84#ifdef PAGE_SIZE
85 /* Help the compiler optimize out the malloc call if PAGE_SIZE
86 is constant and smaller or equal to PTHREAD_STACK_MIN/4. */
87 const size_t buf_size = PAGE_SIZE;
88#else
89 const size_t buf_size = __getpagesize ();
90#endif
91 char *buf;
92
93 if (__libc_use_alloca (buf_size))
94 buf = alloca (buf_size);
95 else
96 {
97 buf = malloc (buf_size);
98 if (buf != NULL)
99 use_malloc = true;
100 else
101 goto out;
102 }
103
104 struct iovec iov = { buf, buf_size };
105
106 if (TEMP_FAILURE_RETRY (__sendto (fd, (void *) &req, sizeof (req), 0,
107 (struct sockaddr *) &nladdr,
108 sizeof (nladdr))) < 0)
109 goto out;
110
111 bool done = false;
112 do
113 {
114 struct msghdr msg =
115 {
116 .msg_name = (void *) &nladdr,
117 .msg_namelen = sizeof (nladdr),
118 .msg_iov = &iov,
119 .msg_iovlen = 1,
120 .msg_control = NULL,
121 .msg_controllen = 0,
122 .msg_flags = 0
123 };
124
125 ssize_t read_len = TEMP_FAILURE_RETRY (__recvmsg (fd, &msg, 0));
126 __netlink_assert_response (fd, read_len);
127 if (read_len < 0)
128 goto out;
129
130 if (msg.msg_flags & MSG_TRUNC)
131 goto out;
132
133 struct nlmsghdr *nlmh;
134 for (nlmh = (struct nlmsghdr *) buf;
135 NLMSG_OK (nlmh, (size_t) read_len);
136 nlmh = (struct nlmsghdr *) NLMSG_NEXT (nlmh, read_len))
137 {
138 if (nladdr.nl_pid != 0 || (pid_t) nlmh->nlmsg_pid != pid
139 || nlmh->nlmsg_seq != req.nlh.nlmsg_seq)
140 continue;
141
142 if (nlmh->nlmsg_type == RTM_NEWLINK)
143 {
144 struct ifinfomsg *ifim = (struct ifinfomsg *) NLMSG_DATA (nlmh);
145 int native = (ifim->ifi_type != ARPHRD_TUNNEL6
146 && ifim->ifi_type != ARPHRD_TUNNEL
147 && ifim->ifi_type != ARPHRD_SIT);
148
149 if (a1_index == ifim->ifi_index)
150 {
151 *a1_native = native;
152 a1_index = 0xffffffffu;
153 }
154 if (a2_index == ifim->ifi_index)
155 {
156 *a2_native = native;
157 a2_index = 0xffffffffu;
158 }
159
160 if (a1_index == 0xffffffffu
161 && a2_index == 0xffffffffu)
162 goto out;
163 }
164 else if (nlmh->nlmsg_type == NLMSG_DONE)
165 /* We found the end, leave the loop. */
166 done = true;
167 }
168 }
169 while (! done);
170
171out:
172 __close_nocancel_nostatus (fd);
173
174 if (use_malloc)
175 free (buf);
176}
177