Head

GCC Code Coverage Report

Directory:	./		Exec	Total	Coverage
File:	usr.sbin/dhcpd/bpf.c	Lines:	0	94	0.0 %
Date:	2017-11-13	Branches:	0	46	0.0 %


/*	$OpenBSD: bpf.c,v 1.19 2017/04/19 05:36:12 natano Exp $	*/

/* BPF socket interface code, originally contributed by Archie Cobbs. */

/*
 * Copyright (c) 1995, 1996, 1998, 1999
 * The Internet Software Consortium.    All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of The Internet Software Consortium nor the names
 *    of its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
 * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * This software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */

#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>

#include <arpa/inet.h>

#include <net/bpf.h>
#include <net/if.h>

#include <netinet/if_ether.h>
#include <netinet/in.h>

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "dhcp.h"
#include "tree.h"
#include "dhcpd.h"
#include "log.h"

ssize_t send_packet	 (struct interface_info *, struct dhcp_packet *,
    size_t, struct in_addr, struct sockaddr_in *, struct hardware *);

/*
 * Called by get_interface_list for each interface that's discovered.
 * Opens a packet filter for each interface and adds it to the select
 * mask.
 */
int
if_register_bpf(struct interface_info *info)
{
	int sock;

	if ((sock = open("/dev/bpf", O_RDWR)) == -1)
		fatal("Can't open bpf device");

	/* Set the BPF device to point at this interface. */
	if (ioctl(sock, BIOCSETIF, info->ifp) == -1)
		fatal("Can't attach interface %s to bpf device", info->name);

	info->send_packet = send_packet;
	return (sock);
}

void
if_register_send(struct interface_info *info)
{
	/*
	 * If we're using the bpf API for sending and receiving, we
	 * don't need to register this interface twice.
	 */
	info->wfdesc = info->rfdesc;
}

/*
 * Packet read filter program: 'ip and udp and dst port bootps'
 */
struct bpf_insn dhcp_bpf_filter[] = {
	/* Make sure this is an IP packet... */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),

	/* Make sure it's a UDP packet... */
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),

	/* Make sure this isn't a fragment... */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),

	/* Get the IP header length... */
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),

	/* Make sure it's to the right port... */
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),

	/* If we passed all the tests, ask for the whole packet. */
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),

	/* Otherwise, drop it. */
	BPF_STMT(BPF_RET+BPF_K, 0),
};

int dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn);


/*
 * Packet write filter program:
 * 'ip and udp and src port bootps and dst port (bootps or bootpc)'
 */
struct bpf_insn dhcp_bpf_wfilter[] = {
	/* Make sure this is an IP packet... */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 11),

	/* Make sure it's a UDP packet... */
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 9),

	/* Make sure this isn't a fragment... */
	BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 7, 0),

	/* Get the IP header length... */
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),

	/* Make sure it's from the right port... */
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 4),

	/* Make sure it is to the right ports ... */
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, CLIENT_PORT, 1, 0),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),

	/* If we passed all the tests, ask for the whole packet. */
	BPF_STMT(BPF_RET+BPF_K, (u_int)-1),

	/* Otherwise, drop it. */
	BPF_STMT(BPF_RET+BPF_K, 0),
};

int dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn);

void
if_register_receive(struct interface_info *info)
{
	struct bpf_version v;
	struct bpf_program p;
	int flag = 1, sz, cmplt = 0;

	/* Open a BPF device and hang it on this interface... */
	info->rfdesc = if_register_bpf(info);

	/* Make sure the BPF version is in range... */
	if (ioctl(info->rfdesc, BIOCVERSION, &v) == -1)
		fatal("Can't get BPF version");

	if (v.bv_major != BPF_MAJOR_VERSION ||
	    v.bv_minor < BPF_MINOR_VERSION)
		fatalx("Kernel BPF version out of range - recompile dhcpd!");

	/*
	 * Set immediate mode so that reads return as soon as a packet
	 * comes in, rather than waiting for the input buffer to fill
	 * with packets.
	 */
	if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) == -1)
		fatal("Can't set immediate mode on bpf device");

	if (ioctl(info->rfdesc, BIOCSFILDROP, &flag) == -1)
		fatal("Can't set filter-drop mode on bpf device");

	/* make sure kernel fills in the source ethernet address */
	if (ioctl(info->rfdesc, BIOCSHDRCMPLT, &cmplt) == -1)
		fatal("Can't set header complete flag on bpf device");

	/* Get the required BPF buffer length from the kernel. */
	if (ioctl(info->rfdesc, BIOCGBLEN, &sz) == -1)
		fatal("Can't get bpf buffer length");
	info->rbuf_max = sz;
	info->rbuf = malloc(info->rbuf_max);
	if (!info->rbuf)
		fatalx("Can't allocate %lu bytes for bpf input buffer.",
		    (unsigned long)info->rbuf_max);
	info->rbuf_offset = 0;
	info->rbuf_len = 0;

	/* Set up the bpf filter program structure. */
	p.bf_len = dhcp_bpf_filter_len;
	p.bf_insns = dhcp_bpf_filter;

	if (ioctl(info->rfdesc, BIOCSETF, &p) == -1)
		fatal("Can't install packet filter program");

	/* Set up the bpf write filter program structure. */
	p.bf_len = dhcp_bpf_wfilter_len;
	p.bf_insns = dhcp_bpf_wfilter;

	if (ioctl(info->rfdesc, BIOCSETWF, &p) == -1)
		fatal("Can't install write filter program");

	/* make sure these settings cannot be changed after dropping privs */
	if (ioctl(info->rfdesc, BIOCLOCK) == -1)
		fatal("Failed to lock bpf descriptor");
}

ssize_t
send_packet(struct interface_info *interface, struct dhcp_packet *raw,
    size_t len, struct in_addr from, struct sockaddr_in *to,
    struct hardware *hto)
{
	unsigned char buf[256];
	struct iovec iov[2];
	ssize_t result;
	int bufp = 0;

	/* Assemble the headers... */
	assemble_hw_header(interface, buf, &bufp, hto);
	assemble_udp_ip_header(interface, buf, &bufp, from.s_addr,
	    to->sin_addr.s_addr, to->sin_port, (unsigned char *)raw, len);

	/* Fire it off */
	iov[0].iov_base = (char *)buf;
	iov[0].iov_len = bufp;
	iov[1].iov_base = (char *)raw;
	iov[1].iov_len = len;

	result = writev(interface->wfdesc, iov, 2);
	if (result == -1)
		log_warn("send_packet");
	return (result);
}

ssize_t
receive_packet(struct interface_info *interface, unsigned char *buf,
    size_t len, struct sockaddr_in *from, struct hardware *hfrom)
{
	int length = 0, offset = 0;
	struct bpf_hdr hdr;

	/*
	 * All this complexity is because BPF doesn't guarantee that
	 * only one packet will be returned at a time.  We're getting
	 * what we deserve, though - this is a terrible abuse of the BPF
	 * interface.  Sigh.
	 */

	/* Process packets until we get one we can return or until we've
	 * done a read and gotten nothing we can return...
	 */
	do {
		/* If the buffer is empty, fill it. */
		if (interface->rbuf_offset >= interface->rbuf_len) {
			length = read(interface->rfdesc, interface->rbuf,
			    interface->rbuf_max);
			if (length <= 0)
				return (length);
			interface->rbuf_offset = 0;
			interface->rbuf_len = length;
		}

		/*
		 * If there isn't room for a whole bpf header, something
		 * went wrong, but we'll ignore it and hope it goes
		 * away... XXX
		 */
		if (interface->rbuf_len - interface->rbuf_offset <
		    sizeof(hdr)) {
			interface->rbuf_offset = interface->rbuf_len;
			continue;
		}

		/* Copy out a bpf header... */
		memcpy(&hdr, &interface->rbuf[interface->rbuf_offset],
		    sizeof(hdr));

		/*
		 * If the bpf header plus data doesn't fit in what's
		 * left of the buffer, stick head in sand yet again...
		 */
		if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen >
		    interface->rbuf_len) {
			interface->rbuf_offset = interface->rbuf_len;
			continue;
		}

		/*
		 * If the captured data wasn't the whole packet, or if
		 * the packet won't fit in the input buffer, all we can
		 * do is drop it.
		 */
		if (hdr.bh_caplen != hdr.bh_datalen) {
			interface->rbuf_offset = BPF_WORDALIGN(
			    interface->rbuf_offset + hdr.bh_hdrlen +
			    hdr.bh_caplen);
			continue;
		}

		/* Skip over the BPF header... */
		interface->rbuf_offset += hdr.bh_hdrlen;

		/* Decode the physical header... */
		offset = decode_hw_header(interface->rbuf +
		    interface->rbuf_offset, hdr.bh_caplen, hfrom);

		/*
		 * If a physical layer checksum failed (dunno of any
		 * physical layer that supports this, but WTH), skip
		 * this packet.
		 */
		if (offset < 0) {
			interface->rbuf_offset = BPF_WORDALIGN(
			    interface->rbuf_offset + hdr.bh_caplen);
			continue;
		}
		interface->rbuf_offset += offset;
		hdr.bh_caplen -= offset;

		/* Decode the IP and UDP headers... */
		offset = decode_udp_ip_header(interface->rbuf +
		    interface->rbuf_offset, hdr.bh_caplen, from);

		/* If the IP or UDP checksum was bad, skip the packet... */
		if (offset < 0) {
			interface->rbuf_offset = BPF_WORDALIGN(
			    interface->rbuf_offset + hdr.bh_caplen);
			continue;
		}
		interface->rbuf_offset += offset;
		hdr.bh_caplen -= offset;

		/*
		 * If there's not enough room to stash the packet data,
		 * we have to skip it (this shouldn't happen in real
		 * life, though).
		 */
		if (hdr.bh_caplen > len) {
			interface->rbuf_offset = BPF_WORDALIGN(
			    interface->rbuf_offset + hdr.bh_caplen);
			continue;
		}

		/* Copy out the data in the packet... */
		memcpy(buf, interface->rbuf + interface->rbuf_offset,
		    hdr.bh_caplen);
		interface->rbuf_offset = BPF_WORDALIGN(interface->rbuf_offset +
		    hdr.bh_caplen);
		return (hdr.bh_caplen);
	} while (!length);
	return (0);
}


Generated by: GCOVR (Version 3.3)

Line	Branch	Exec	Source
1			/* $OpenBSD: bpf.c,v 1.19 2017/04/19 05:36:12 natano Exp $ */
2
3			/* BPF socket interface code, originally contributed by Archie Cobbs. */
4
5			/*
6			* Copyright (c) 1995, 1996, 1998, 1999
7			* The Internet Software Consortium. All rights reserved.
8			*
9			* Redistribution and use in source and binary forms, with or without
10			* modification, are permitted provided that the following conditions
11			* are met:
12			*
13			* 1. Redistributions of source code must retain the above copyright
14			* notice, this list of conditions and the following disclaimer.
15			* 2. Redistributions in binary form must reproduce the above copyright
16			* notice, this list of conditions and the following disclaimer in the
17			* documentation and/or other materials provided with the distribution.
18			* 3. Neither the name of The Internet Software Consortium nor the names
19			* of its contributors may be used to endorse or promote products derived
20			* from this software without specific prior written permission.
21			*
22			* THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
23			* CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
24			* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
25			* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
26			* DISCLAIMED. IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
27			* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28			* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
29			* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
30			* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
31			* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
32			* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
33			* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34			* SUCH DAMAGE.
35			*
36			* This software has been written for the Internet Software Consortium
37			* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
38			* Enterprises. To learn more about the Internet Software Consortium,
39			* see ``http://www.vix.com/isc''. To learn more about Vixie
40			* Enterprises, see ``http://www.vix.com''.
41			*/
42
43			#include <sys/ioctl.h>
44			#include <sys/types.h>
45			#include <sys/socket.h>
46
47			#include <arpa/inet.h>
48
49			#include <net/bpf.h>
50			#include <net/if.h>
51
52			#include <netinet/if_ether.h>
53			#include <netinet/in.h>
54
55			#include <errno.h>
56			#include <fcntl.h>
57			#include <stdio.h>
58			#include <stdlib.h>
59			#include <string.h>
60			#include <unistd.h>
61
62			#include "dhcp.h"
63			#include "tree.h"
64			#include "dhcpd.h"
65			#include "log.h"
66
67			ssize_t send_packet (struct interface_info , struct dhcp_packet ,
68			size_t, struct in_addr, struct sockaddr_in , struct hardware );
69
70			/*
71			* Called by get_interface_list for each interface that's discovered.
72			* Opens a packet filter for each interface and adds it to the select
73			* mask.
74			*/
75			int
76			if_register_bpf(struct interface_info *info)
77			{
78			int sock;
79
80			if ((sock = open("/dev/bpf", O_RDWR)) == -1)
81			fatal("Can't open bpf device");
82
83			/* Set the BPF device to point at this interface. */
84			if (ioctl(sock, BIOCSETIF, info->ifp) == -1)
85			fatal("Can't attach interface %s to bpf device", info->name);
86
87			info->send_packet = send_packet;
88			return (sock);
89			}
90
91			void
92			if_register_send(struct interface_info *info)
93			{
94			/*
95			* If we're using the bpf API for sending and receiving, we
96			* don't need to register this interface twice.
97			*/
98			info->wfdesc = info->rfdesc;
99			}
100
101			/*
102			* Packet read filter program: 'ip and udp and dst port bootps'
103			*/
104			struct bpf_insn dhcp_bpf_filter[] = {
105			/* Make sure this is an IP packet... */
106			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
107			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
108
109			/* Make sure it's a UDP packet... */
110			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
111			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
112
113			/* Make sure this isn't a fragment... */
114			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
115			BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
116
117			/* Get the IP header length... */
118			BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
119
120			/* Make sure it's to the right port... */
121			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
122			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
123
124			/* If we passed all the tests, ask for the whole packet. */
125			BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
126
127			/* Otherwise, drop it. */
128			BPF_STMT(BPF_RET+BPF_K, 0),
129			};
130
131			int dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn);
132
133
134			/*
135			* Packet write filter program:
136			* 'ip and udp and src port bootps and dst port (bootps or bootpc)'
137			*/
138			struct bpf_insn dhcp_bpf_wfilter[] = {
139			/* Make sure this is an IP packet... */
140			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
141			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 11),
142
143			/* Make sure it's a UDP packet... */
144			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
145			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 9),
146
147			/* Make sure this isn't a fragment... */
148			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
149			BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 7, 0),
150
151			/* Get the IP header length... */
152			BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
153
154			/* Make sure it's from the right port... */
155			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
156			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 4),
157
158			/* Make sure it is to the right ports ... */
159			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
160			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, CLIENT_PORT, 1, 0),
161			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
162
163			/* If we passed all the tests, ask for the whole packet. */
164			BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
165
166			/* Otherwise, drop it. */
167			BPF_STMT(BPF_RET+BPF_K, 0),
168			};
169
170			int dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn);
171
172			void
173			if_register_receive(struct interface_info *info)
174			{
175			struct bpf_version v;
176			struct bpf_program p;
177			int flag = 1, sz, cmplt = 0;
178
179			/* Open a BPF device and hang it on this interface... */
180			info->rfdesc = if_register_bpf(info);
181
182			/* Make sure the BPF version is in range... */
183			if (ioctl(info->rfdesc, BIOCVERSION, &v) == -1)
184			fatal("Can't get BPF version");
185
186			if (v.bv_major != BPF_MAJOR_VERSION \|\|
187			v.bv_minor < BPF_MINOR_VERSION)
188			fatalx("Kernel BPF version out of range - recompile dhcpd!");
189
190			/*
191			* Set immediate mode so that reads return as soon as a packet
192			* comes in, rather than waiting for the input buffer to fill
193			* with packets.
194			*/
195			if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) == -1)
196			fatal("Can't set immediate mode on bpf device");
197
198			if (ioctl(info->rfdesc, BIOCSFILDROP, &flag) == -1)
199			fatal("Can't set filter-drop mode on bpf device");
200
201			/* make sure kernel fills in the source ethernet address */
202			if (ioctl(info->rfdesc, BIOCSHDRCMPLT, &cmplt) == -1)
203			fatal("Can't set header complete flag on bpf device");
204
205			/* Get the required BPF buffer length from the kernel. */
206			if (ioctl(info->rfdesc, BIOCGBLEN, &sz) == -1)
207			fatal("Can't get bpf buffer length");
208			info->rbuf_max = sz;
209			info->rbuf = malloc(info->rbuf_max);
210			if (!info->rbuf)
211			fatalx("Can't allocate %lu bytes for bpf input buffer.",
212			(unsigned long)info->rbuf_max);
213			info->rbuf_offset = 0;
214			info->rbuf_len = 0;
215
216			/* Set up the bpf filter program structure. */
217			p.bf_len = dhcp_bpf_filter_len;
218			p.bf_insns = dhcp_bpf_filter;
219
220			if (ioctl(info->rfdesc, BIOCSETF, &p) == -1)
221			fatal("Can't install packet filter program");
222
223			/* Set up the bpf write filter program structure. */
224			p.bf_len = dhcp_bpf_wfilter_len;
225			p.bf_insns = dhcp_bpf_wfilter;
226
227			if (ioctl(info->rfdesc, BIOCSETWF, &p) == -1)
228			fatal("Can't install write filter program");
229
230			/* make sure these settings cannot be changed after dropping privs */
231			if (ioctl(info->rfdesc, BIOCLOCK) == -1)
232			fatal("Failed to lock bpf descriptor");
233			}
234
235			ssize_t
236			send_packet(struct interface_info interface, struct dhcp_packet raw,
237			size_t len, struct in_addr from, struct sockaddr_in *to,
238			struct hardware *hto)
239			{
240			unsigned char buf[256];
241			struct iovec iov[2];
242			ssize_t result;
243			int bufp = 0;
244
245			/* Assemble the headers... */
246			assemble_hw_header(interface, buf, &bufp, hto);
247			assemble_udp_ip_header(interface, buf, &bufp, from.s_addr,
248			to->sin_addr.s_addr, to->sin_port, (unsigned char *)raw, len);
249
250			/* Fire it off */
251			iov[0].iov_base = (char *)buf;
252			iov[0].iov_len = bufp;
253			iov[1].iov_base = (char *)raw;
254			iov[1].iov_len = len;
255
256			result = writev(interface->wfdesc, iov, 2);
257			if (result == -1)
258			log_warn("send_packet");
259			return (result);
260			}
261
262			ssize_t
263			receive_packet(struct interface_info interface, unsigned char buf,
264			size_t len, struct sockaddr_in from, struct hardware hfrom)
265			{
266			int length = 0, offset = 0;
267			struct bpf_hdr hdr;
268
269			/*
270			* All this complexity is because BPF doesn't guarantee that
271			* only one packet will be returned at a time. We're getting
272			* what we deserve, though - this is a terrible abuse of the BPF
273			* interface. Sigh.
274			*/
275
276			/* Process packets until we get one we can return or until we've
277			* done a read and gotten nothing we can return...
278			*/
279			do {
280			/* If the buffer is empty, fill it. */
281			if (interface->rbuf_offset >= interface->rbuf_len) {
282			length = read(interface->rfdesc, interface->rbuf,
283			interface->rbuf_max);
284			if (length <= 0)
285			return (length);
286			interface->rbuf_offset = 0;
287			interface->rbuf_len = length;
288			}
289
290			/*
291			* If there isn't room for a whole bpf header, something
292			* went wrong, but we'll ignore it and hope it goes
293			* away... XXX
294			*/
295			if (interface->rbuf_len - interface->rbuf_offset <
296			sizeof(hdr)) {
297			interface->rbuf_offset = interface->rbuf_len;
298			continue;
299			}
300
301			/* Copy out a bpf header... */
302			memcpy(&hdr, &interface->rbuf[interface->rbuf_offset],
303			sizeof(hdr));
304
305			/*
306			* If the bpf header plus data doesn't fit in what's
307			* left of the buffer, stick head in sand yet again...
308			*/
309			if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen >
310			interface->rbuf_len) {
311			interface->rbuf_offset = interface->rbuf_len;
312			continue;
313			}
314
315			/*
316			* If the captured data wasn't the whole packet, or if
317			* the packet won't fit in the input buffer, all we can
318			* do is drop it.
319			*/
320			if (hdr.bh_caplen != hdr.bh_datalen) {
321			interface->rbuf_offset = BPF_WORDALIGN(
322			interface->rbuf_offset + hdr.bh_hdrlen +
323			hdr.bh_caplen);
324			continue;
325			}
326
327			/* Skip over the BPF header... */
328			interface->rbuf_offset += hdr.bh_hdrlen;
329
330			/* Decode the physical header... */
331			offset = decode_hw_header(interface->rbuf +
332			interface->rbuf_offset, hdr.bh_caplen, hfrom);
333
334			/*
335			* If a physical layer checksum failed (dunno of any
336			* physical layer that supports this, but WTH), skip
337			* this packet.
338			*/
339			if (offset < 0) {
340			interface->rbuf_offset = BPF_WORDALIGN(
341			interface->rbuf_offset + hdr.bh_caplen);
342			continue;
343			}
344			interface->rbuf_offset += offset;
345			hdr.bh_caplen -= offset;
346
347			/* Decode the IP and UDP headers... */
348			offset = decode_udp_ip_header(interface->rbuf +
349			interface->rbuf_offset, hdr.bh_caplen, from);
350
351			/* If the IP or UDP checksum was bad, skip the packet... */
352			if (offset < 0) {
353			interface->rbuf_offset = BPF_WORDALIGN(
354			interface->rbuf_offset + hdr.bh_caplen);
355			continue;
356			}
357			interface->rbuf_offset += offset;
358			hdr.bh_caplen -= offset;
359
360			/*
361			* If there's not enough room to stash the packet data,
362			* we have to skip it (this shouldn't happen in real
363			* life, though).
364			*/
365			if (hdr.bh_caplen > len) {
366			interface->rbuf_offset = BPF_WORDALIGN(
367			interface->rbuf_offset + hdr.bh_caplen);
368			continue;
369			}
370
371			/* Copy out the data in the packet... */
372			memcpy(buf, interface->rbuf + interface->rbuf_offset,
373			hdr.bh_caplen);
374			interface->rbuf_offset = BPF_WORDALIGN(interface->rbuf_offset +
375			hdr.bh_caplen);
376			return (hdr.bh_caplen);
377			} while (!length);
378			return (0);
379			}