bpf.c revision a3a2260384a906e1674c7498c2f479e9f37bc503 
1/*
2 * dhcpcd - DHCP client daemon
3 * Copyright (c) 2006-2011 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
51int
52open_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
130eexit:
131	free(iface->buffer);
132	iface->buffer = NULL;
133	close(fd);
134	return -1;
135}
136
137ssize_t
138send_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. */
161ssize_t
162get_raw_packet(struct interface *iface, int protocol,
163    void *data, ssize_t len, int *partialcsum)
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	if (partialcsum != NULL)
176		*partialcsum = 0; /* Not supported on BSD */
177
178	for (;;) {
179		if (iface->buffer_len == 0) {
180			bytes = read(fd, iface->buffer, iface->buffer_size);
181			if (bytes == -1)
182				return errno == EAGAIN ? 0 : -1;
183			else if ((size_t)bytes < sizeof(packet))
184				return -1;
185			iface->buffer_len = bytes;
186			iface->buffer_pos = 0;
187		}
188		bytes = -1;
189		memcpy(&packet, iface->buffer + iface->buffer_pos,
190		    sizeof(packet));
191		if (packet.bh_caplen != packet.bh_datalen)
192			goto next; /* Incomplete packet, drop. */
193		if (iface->buffer_pos + packet.bh_caplen + packet.bh_hdrlen >
194		    iface->buffer_len)
195			goto next; /* Packet beyond buffer, drop. */
196		payload = iface->buffer + packet.bh_hdrlen + ETHER_HDR_LEN;
197		bytes = packet.bh_caplen - ETHER_HDR_LEN;
198		if (bytes > len)
199			bytes = len;
200		memcpy(data, payload, bytes);
201next:
202		iface->buffer_pos += BPF_WORDALIGN(packet.bh_hdrlen +
203		    packet.bh_caplen);
204		if (iface->buffer_pos >= iface->buffer_len)
205			iface->buffer_len = iface->buffer_pos = 0;
206		if (bytes != -1)
207			return bytes;
208	}
209}
210