1 /*
2 * dhcpcd - DHCP client daemon
3 * Copyright (c) 2006-2008 Roy Marples <roy@marples.name>
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/types.h>
28 #include <sys/ioctl.h>
29 #include <sys/socket.h>
30 #include <sys/uio.h>
31
32 #include <net/bpf.h>
33 #include <net/if.h>
34 #include <arpa/inet.h>
35
36 #include <errno.h>
37 #include <fcntl.h>
38 #include <paths.h>
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <string.h>
42 #include <syslog.h>
43 #include <unistd.h>
44
45 #include "config.h"
46 #include "common.h"
47 #include "dhcp.h"
48 #include "net.h"
49 #include "bpf-filter.h"
50
51 int
open_socket(struct interface * iface,int protocol)52 open_socket(struct interface *iface, int protocol)
53 {
54 int fd = -1;
55 int *fdp = NULL;
56 struct ifreq ifr;
57 int buf_len = 0;
58 struct bpf_version pv;
59 struct bpf_program pf;
60 #ifdef BIOCIMMEDIATE
61 int flags;
62 #endif
63 #ifdef _PATH_BPF
64 fd = open(_PATH_BPF, O_RDWR | O_NONBLOCK);
65 #else
66 char *device;
67 int n = 0;
68
69 device = xmalloc(sizeof(char) * PATH_MAX);
70 do {
71 snprintf(device, PATH_MAX, "/dev/bpf%d", n++);
72 fd = open(device, O_RDWR | O_NONBLOCK);
73 } while (fd == -1 && errno == EBUSY);
74 free(device);
75 #endif
76
77 if (fd == -1)
78 return -1;
79
80 if (ioctl(fd, BIOCVERSION, &pv) == -1)
81 goto eexit;
82 if (pv.bv_major != BPF_MAJOR_VERSION ||
83 pv.bv_minor < BPF_MINOR_VERSION) {
84 syslog(LOG_ERR, "BPF version mismatch - recompile");
85 goto eexit;
86 }
87
88 memset(&ifr, 0, sizeof(ifr));
89 strlcpy(ifr.ifr_name, iface->name, sizeof(ifr.ifr_name));
90 if (ioctl(fd, BIOCSETIF, &ifr) == -1)
91 goto eexit;
92
93 /* Get the required BPF buffer length from the kernel. */
94 if (ioctl(fd, BIOCGBLEN, &buf_len) == -1)
95 goto eexit;
96 if (iface->buffer_size != (size_t)buf_len) {
97 free(iface->buffer);
98 iface->buffer_size = buf_len;
99 iface->buffer = xmalloc(buf_len);
100 iface->buffer_len = iface->buffer_pos = 0;
101 }
102
103 #ifdef BIOCIMMEDIATE
104 flags = 1;
105 if (ioctl(fd, BIOCIMMEDIATE, &flags) == -1)
106 goto eexit;
107 #endif
108
109 /* Install the DHCP filter */
110 if (protocol == ETHERTYPE_ARP) {
111 pf.bf_insns = UNCONST(arp_bpf_filter);
112 pf.bf_len = arp_bpf_filter_len;
113 fdp = &iface->arp_fd;
114 } else {
115 pf.bf_insns = UNCONST(dhcp_bpf_filter);
116 pf.bf_len = dhcp_bpf_filter_len;
117 fdp = &iface->raw_fd;
118 }
119 if (ioctl(fd, BIOCSETF, &pf) == -1)
120 goto eexit;
121 if (set_cloexec(fd) == -1)
122 goto eexit;
123 if (fdp) {
124 if (*fdp != -1)
125 close(*fdp);
126 *fdp = fd;
127 }
128 return fd;
129
130 eexit:
131 free(iface->buffer);
132 iface->buffer = NULL;
133 close(fd);
134 return -1;
135 }
136
137 ssize_t
send_raw_packet(const struct interface * iface,int protocol,const void * data,ssize_t len)138 send_raw_packet(const struct interface *iface, int protocol,
139 const void *data, ssize_t len)
140 {
141 struct iovec iov[2];
142 struct ether_header hw;
143 int fd;
144
145 memset(&hw, 0, ETHER_HDR_LEN);
146 memset(&hw.ether_dhost, 0xff, ETHER_ADDR_LEN);
147 hw.ether_type = htons(protocol);
148 iov[0].iov_base = &hw;
149 iov[0].iov_len = ETHER_HDR_LEN;
150 iov[1].iov_base = UNCONST(data);
151 iov[1].iov_len = len;
152 if (protocol == ETHERTYPE_ARP)
153 fd = iface->arp_fd;
154 else
155 fd = iface->raw_fd;
156 return writev(fd, iov, 2);
157 }
158
159 /* BPF requires that we read the entire buffer.
160 * So we pass the buffer in the API so we can loop on >1 packet. */
161 ssize_t
get_raw_packet(struct interface * iface,int protocol,void * data,ssize_t len)162 get_raw_packet(struct interface *iface, int protocol,
163 void *data, ssize_t len)
164 {
165 int fd = -1;
166 struct bpf_hdr packet;
167 ssize_t bytes;
168 const unsigned char *payload;
169
170 if (protocol == ETHERTYPE_ARP)
171 fd = iface->arp_fd;
172 else
173 fd = iface->raw_fd;
174
175 for (;;) {
176 if (iface->buffer_len == 0) {
177 bytes = read(fd, iface->buffer, iface->buffer_size);
178 if (bytes == -1)
179 return errno == EAGAIN ? 0 : -1;
180 else if ((size_t)bytes < sizeof(packet))
181 return -1;
182 iface->buffer_len = bytes;
183 iface->buffer_pos = 0;
184 }
185 bytes = -1;
186 memcpy(&packet, iface->buffer + iface->buffer_pos,
187 sizeof(packet));
188 if (packet.bh_caplen != packet.bh_datalen)
189 goto next; /* Incomplete packet, drop. */
190 if (iface->buffer_pos + packet.bh_caplen + packet.bh_hdrlen >
191 iface->buffer_len)
192 goto next; /* Packet beyond buffer, drop. */
193 payload = iface->buffer + packet.bh_hdrlen + ETHER_HDR_LEN;
194 bytes = packet.bh_caplen - ETHER_HDR_LEN;
195 if (bytes > len)
196 bytes = len;
197 memcpy(data, payload, bytes);
198 next:
199 iface->buffer_pos += BPF_WORDALIGN(packet.bh_hdrlen +
200 packet.bh_caplen);
201 if (iface->buffer_pos >= iface->buffer_len)
202 iface->buffer_len = iface->buffer_pos = 0;
203 if (bytes != -1)
204 return bytes;
205 }
206 }
207