1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
4  */
5 
6 #include <stdio.h>
7 #include <unistd.h>
8 #include <errno.h>
9 #include <string.h>
10 #include <linux/if_tun.h>
11 #include <net/if.h>
12 #include <sys/ioctl.h>
13 #include <sys/socket.h>
14 #include <sys/wait.h>
15 #include <sys/uio.h>
16 #include <kern_util.h>
17 #include <os.h>
18 #include "tuntap.h"
19 
20 static int tuntap_user_init(void *data, void *dev)
21 {
22 	struct tuntap_data *pri = data;
23 
24 	pri->dev = dev;
25 	return 0;
26 }
27 
28 static void tuntap_add_addr(unsigned char *addr, unsigned char *netmask,
29 			    void *data)
30 {
31 	struct tuntap_data *pri = data;
32 
33 	tap_check_ips(pri->gate_addr, addr);
34 	if ((pri->fd == -1) || pri->fixed_config)
35 		return;
36 	open_addr(addr, netmask, pri->dev_name);
37 }
38 
39 static void tuntap_del_addr(unsigned char *addr, unsigned char *netmask,
40 			    void *data)
41 {
42 	struct tuntap_data *pri = data;
43 
44 	if ((pri->fd == -1) || pri->fixed_config)
45 		return;
46 	close_addr(addr, netmask, pri->dev_name);
47 }
48 
49 struct tuntap_pre_exec_data {
50 	int stdout_fd;
51 	int close_me;
52 };
53 
54 static void tuntap_pre_exec(void *arg)
55 {
56 	struct tuntap_pre_exec_data *data = arg;
57 
58 	dup2(data->stdout_fd, 1);
59 	close(data->close_me);
60 }
61 
62 static int tuntap_open_tramp(char *gate, int *fd_out, int me, int remote,
63 			     char *buffer, int buffer_len, int *used_out)
64 {
65 	struct tuntap_pre_exec_data data;
66 	char version_buf[sizeof("nnnnn\0")];
67 	char *argv[] = { "uml_net", version_buf, "tuntap", "up", gate,
68 			 NULL };
69 	char buf[CMSG_SPACE(sizeof(*fd_out))];
70 	struct msghdr msg;
71 	struct cmsghdr *cmsg;
72 	struct iovec iov;
73 	int pid, n, err;
74 
75 	sprintf(version_buf, "%d", UML_NET_VERSION);
76 
77 	data.stdout_fd = remote;
78 	data.close_me = me;
79 
80 	pid = run_helper(tuntap_pre_exec, &data, argv);
81 
82 	if (pid < 0)
83 		return pid;
84 
85 	close(remote);
86 
87 	msg.msg_name = NULL;
88 	msg.msg_namelen = 0;
89 	if (buffer != NULL) {
90 		iov = ((struct iovec) { buffer, buffer_len });
91 		msg.msg_iov = &iov;
92 		msg.msg_iovlen = 1;
93 	}
94 	else {
95 		msg.msg_iov = NULL;
96 		msg.msg_iovlen = 0;
97 	}
98 	msg.msg_control = buf;
99 	msg.msg_controllen = sizeof(buf);
100 	msg.msg_flags = 0;
101 	n = recvmsg(me, &msg, 0);
102 	*used_out = n;
103 	if (n < 0) {
104 		err = -errno;
105 		printk(UM_KERN_ERR "tuntap_open_tramp : recvmsg failed - "
106 		       "errno = %d\n", errno);
107 		return err;
108 	}
109 	helper_wait(pid);
110 
111 	cmsg = CMSG_FIRSTHDR(&msg);
112 	if (cmsg == NULL) {
113 		printk(UM_KERN_ERR "tuntap_open_tramp : didn't receive a "
114 		       "message\n");
115 		return -EINVAL;
116 	}
117 	if ((cmsg->cmsg_level != SOL_SOCKET) ||
118 	   (cmsg->cmsg_type != SCM_RIGHTS)) {
119 		printk(UM_KERN_ERR "tuntap_open_tramp : didn't receive a "
120 		       "descriptor\n");
121 		return -EINVAL;
122 	}
123 	*fd_out = ((int *) CMSG_DATA(cmsg))[0];
124 	os_set_exec_close(*fd_out);
125 	return 0;
126 }
127 
128 static int tuntap_open(void *data)
129 {
130 	struct ifreq ifr;
131 	struct tuntap_data *pri = data;
132 	char *output, *buffer;
133 	int err, fds[2], len, used;
134 
135 	err = tap_open_common(pri->dev, pri->gate_addr);
136 	if (err < 0)
137 		return err;
138 
139 	if (pri->fixed_config) {
140 		pri->fd = os_open_file("/dev/net/tun",
141 				       of_cloexec(of_rdwr(OPENFLAGS())), 0);
142 		if (pri->fd < 0) {
143 			printk(UM_KERN_ERR "Failed to open /dev/net/tun, "
144 			       "err = %d\n", -pri->fd);
145 			return pri->fd;
146 		}
147 		memset(&ifr, 0, sizeof(ifr));
148 		ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
149 		strscpy(ifr.ifr_name, pri->dev_name, sizeof(ifr.ifr_name));
150 		if (ioctl(pri->fd, TUNSETIFF, &ifr) < 0) {
151 			err = -errno;
152 			printk(UM_KERN_ERR "TUNSETIFF failed, errno = %d\n",
153 			       errno);
154 			close(pri->fd);
155 			return err;
156 		}
157 	}
158 	else {
159 		err = socketpair(AF_UNIX, SOCK_DGRAM, 0, fds);
160 		if (err) {
161 			err = -errno;
162 			printk(UM_KERN_ERR "tuntap_open : socketpair failed - "
163 			       "errno = %d\n", errno);
164 			return err;
165 		}
166 
167 		buffer = get_output_buffer(&len);
168 		if (buffer != NULL)
169 			len--;
170 		used = 0;
171 
172 		err = tuntap_open_tramp(pri->gate_addr, &pri->fd, fds[0],
173 					fds[1], buffer, len, &used);
174 
175 		output = buffer;
176 		if (err < 0) {
177 			printk("%s", output);
178 			free_output_buffer(buffer);
179 			printk(UM_KERN_ERR "tuntap_open_tramp failed - "
180 			       "err = %d\n", -err);
181 			return err;
182 		}
183 
184 		pri->dev_name = uml_strdup(buffer);
185 		output += IFNAMSIZ;
186 		printk("%s", output);
187 		free_output_buffer(buffer);
188 
189 		close(fds[0]);
190 		iter_addresses(pri->dev, open_addr, pri->dev_name);
191 	}
192 
193 	return pri->fd;
194 }
195 
196 static void tuntap_close(int fd, void *data)
197 {
198 	struct tuntap_data *pri = data;
199 
200 	if (!pri->fixed_config)
201 		iter_addresses(pri->dev, close_addr, pri->dev_name);
202 	close(fd);
203 	pri->fd = -1;
204 }
205 
206 const struct net_user_info tuntap_user_info = {
207 	.init		= tuntap_user_init,
208 	.open		= tuntap_open,
209 	.close	 	= tuntap_close,
210 	.remove	 	= NULL,
211 	.add_address	= tuntap_add_addr,
212 	.delete_address = tuntap_del_addr,
213 	.mtu		= ETH_MAX_PACKET,
214 	.max_packet	= ETH_MAX_PACKET + ETH_HEADER_OTHER,
215 };
216