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GCC Code Coverage Report

Directory:	./		Exec	Total	Coverage
File:	usr.sbin/dhcrelay/bpf.c	Lines:	0	98	0.0 %
Date:	2017-11-13	Branches:	0	54	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/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>

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

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

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

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

/*
 * 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;

	/* Open the BPF device */
	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->ifr) == -1)
		fatal("Can't attach interface %s to bpf device", info->name);

	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 filter program: 'ip and udp and dst port CLIENT_PORT'
 */
struct bpf_insn dhcp_bpf_sfilter[] = {
	/* 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, CLIENT_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_sfilter_len = sizeof(dhcp_bpf_sfilter) / sizeof(struct bpf_insn);

/*
 * Packet filter program: 'ip and udp and dst port SERVER_PORT'
 */
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 filter program: encapsulated 'ip and udp and dst port SERVER_PORT'
 */
struct bpf_insn dhcp_bpf_efilter[] = {
	/* Make sure this is an encapsulated AF_INET packet... */
	BPF_STMT(BPF_LD + BPF_W + BPF_ABS, 0),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, AF_INET << 24, 0, 10),

	/* Make sure it's an IPIP packet... */
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 21),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_IPIP, 0, 8),

	/* Make sure it's an encapsulated UDP packet... */
	BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 41),
	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, 38),
	BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),

	/* Get the IP header length... */
	BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 32),

	/* Make sure it's to the right port... */
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 34),
	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_efilter_len = sizeof(dhcp_bpf_efilter) / sizeof(struct bpf_insn);

/*
 * Packet write filter program: 'ip and udp and src port CLIENT_PORT'
 */
struct bpf_insn dhcp_bpf_swfilter[] = {
	/* 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 from the right port... */
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
	BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, CLIENT_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_swfilter_len = sizeof(dhcp_bpf_swfilter) /
	sizeof(struct bpf_insn);

/*
 * Packet write filter program: 'ip and udp and src port SERVER_PORT'
 */
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, 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 from the right port... */
	BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
	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, int isserver)
{
	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");

	/* 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. */
	if (isserver) {
		p.bf_len = dhcp_bpf_sfilter_len;
		p.bf_insns = dhcp_bpf_sfilter;
	} else if (info->hw_address.htype == HTYPE_IPSEC_TUNNEL) {
		p.bf_len = dhcp_bpf_efilter_len;
		p.bf_insns = dhcp_bpf_efilter;
	} else {
		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. */
	if (isserver) {
		p.bf_len = dhcp_bpf_swfilter_len;
		p.bf_insns = dhcp_bpf_swfilter;
	} else {
		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 packet_ctx *pc)
{
	unsigned char buf[256];
	struct iovec iov[2];
	ssize_t bufp;
	int result;

	result = -1;

	if (interface->hw_address.htype == HTYPE_IPSEC_TUNNEL) {
		socklen_t slen = pc->pc_dst.ss_len;
		result = sendto(server_fd, raw, len, 0,
		    (struct sockaddr *)&pc->pc_dst, slen);
		goto done;
	}

	/* Assemble the headers... */
	if ((bufp = assemble_hw_header(buf, sizeof(buf), 0, pc,
	    interface->hw_address.htype)) == -1)
		goto done;
	if ((bufp = assemble_udp_ip_header(buf, sizeof(buf), bufp, pc,
	    (unsigned char *)raw, len)) == -1)
		goto done;

	/* 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);
 done:
	if (result == -1)
		log_warn("send_packet");
	return (result);
}

ssize_t
receive_packet(struct interface_info *interface, unsigned char *buf,
    size_t len, struct packet_ctx *pc)
{
	int length = 0;
	ssize_t 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 += 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_len, interface->rbuf_offset, pc,
		    interface->hw_address.htype);

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

		/* Decode the IP and UDP headers... */
		offset = decode_udp_ip_header(interface->rbuf,
		    interface->rbuf_len, offset, pc);

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

		hdr.bh_caplen -= offset - interface->rbuf_offset;
		interface->rbuf_offset = 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 += hdr.bh_caplen;
			continue;
		}

		/* Copy out the data in the packet... */
		memcpy(buf, interface->rbuf + interface->rbuf_offset,
		    hdr.bh_caplen);
		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/types.h>
44			#include <sys/ioctl.h>
45			#include <sys/socket.h>
46
47			#include <net/bpf.h>
48			#include <net/if.h>
49
50			#include <netinet/in.h>
51			#include <netinet/if_ether.h>
52
53			#include <errno.h>
54			#include <fcntl.h>
55			#include <stdio.h>
56			#include <stdlib.h>
57			#include <string.h>
58			#include <unistd.h>
59
60			#include "dhcp.h"
61			#include "dhcpd.h"
62			#include "log.h"
63
64			/*
65			* Called by get_interface_list for each interface that's discovered.
66			* Opens a packet filter for each interface and adds it to the select
67			* mask.
68			*/
69			int
70			if_register_bpf(struct interface_info *info)
71			{
72			int sock;
73
74			/* Open the BPF device */
75			if ((sock = open("/dev/bpf", O_RDWR)) == -1)
76			fatal("Can't open bpf device");
77
78			/* Set the BPF device to point at this interface. */
79			if (ioctl(sock, BIOCSETIF, &info->ifr) == -1)
80			fatal("Can't attach interface %s to bpf device", info->name);
81
82			return (sock);
83			}
84
85			void
86			if_register_send(struct interface_info *info)
87			{
88			/*
89			* If we're using the bpf API for sending and receiving, we
90			* don't need to register this interface twice.
91			*/
92			info->wfdesc = info->rfdesc;
93			}
94
95			/*
96			* Packet filter program: 'ip and udp and dst port CLIENT_PORT'
97			*/
98			struct bpf_insn dhcp_bpf_sfilter[] = {
99			/* Make sure this is an IP packet... */
100			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
101			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
102
103			/* Make sure it's a UDP packet... */
104			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
105			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
106
107			/* Make sure this isn't a fragment... */
108			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
109			BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
110
111			/* Get the IP header length... */
112			BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
113
114			/* Make sure it's to the right port... */
115			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
116			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, CLIENT_PORT, 0, 1),
117
118			/* If we passed all the tests, ask for the whole packet. */
119			BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
120
121			/* Otherwise, drop it. */
122			BPF_STMT(BPF_RET+BPF_K, 0),
123			};
124
125			int dhcp_bpf_sfilter_len = sizeof(dhcp_bpf_sfilter) / sizeof(struct bpf_insn);
126
127			/*
128			* Packet filter program: 'ip and udp and dst port SERVER_PORT'
129			*/
130			struct bpf_insn dhcp_bpf_filter[] = {
131			/* Make sure this is an IP packet... */
132			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
133			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
134
135			/* Make sure it's a UDP packet... */
136			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
137			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
138
139			/* Make sure this isn't a fragment... */
140			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
141			BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
142
143			/* Get the IP header length... */
144			BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
145
146			/* Make sure it's to the right port... */
147			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 16),
148			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
149
150			/* If we passed all the tests, ask for the whole packet. */
151			BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
152
153			/* Otherwise, drop it. */
154			BPF_STMT(BPF_RET+BPF_K, 0),
155			};
156
157			int dhcp_bpf_filter_len = sizeof(dhcp_bpf_filter) / sizeof(struct bpf_insn);
158
159			/*
160			* Packet filter program: encapsulated 'ip and udp and dst port SERVER_PORT'
161			*/
162			struct bpf_insn dhcp_bpf_efilter[] = {
163			/* Make sure this is an encapsulated AF_INET packet... */
164			BPF_STMT(BPF_LD + BPF_W + BPF_ABS, 0),
165			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, AF_INET << 24, 0, 10),
166
167			/* Make sure it's an IPIP packet... */
168			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 21),
169			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_IPIP, 0, 8),
170
171			/* Make sure it's an encapsulated UDP packet... */
172			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 41),
173			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
174
175			/* Make sure this isn't a fragment... */
176			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 38),
177			BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
178
179			/* Get the IP header length... */
180			BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 32),
181
182			/* Make sure it's to the right port... */
183			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 34),
184			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
185
186			/* If we passed all the tests, ask for the whole packet. */
187			BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
188
189			/* Otherwise, drop it. */
190			BPF_STMT(BPF_RET+BPF_K, 0),
191			};
192
193			int dhcp_bpf_efilter_len = sizeof(dhcp_bpf_efilter) / sizeof(struct bpf_insn);
194
195			/*
196			* Packet write filter program: 'ip and udp and src port CLIENT_PORT'
197			*/
198			struct bpf_insn dhcp_bpf_swfilter[] = {
199			/* Make sure this is an IP packet... */
200			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
201			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
202
203			/* Make sure it's a UDP packet... */
204			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
205			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
206
207			/* Make sure this isn't a fragment... */
208			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
209			BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
210
211			/* Get the IP header length... */
212			BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
213
214			/* Make sure it's from the right port... */
215			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
216			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, CLIENT_PORT, 0, 1),
217
218			/* If we passed all the tests, ask for the whole packet. */
219			BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
220
221			/* Otherwise, drop it. */
222			BPF_STMT(BPF_RET+BPF_K, 0),
223			};
224
225			int dhcp_bpf_swfilter_len = sizeof(dhcp_bpf_swfilter) /
226			sizeof(struct bpf_insn);
227
228			/*
229			* Packet write filter program: 'ip and udp and src port SERVER_PORT'
230			*/
231			struct bpf_insn dhcp_bpf_wfilter[] = {
232			/* Make sure this is an IP packet... */
233			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 12),
234			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
235
236			/* Make sure it's a UDP packet... */
237			BPF_STMT(BPF_LD + BPF_B + BPF_ABS, 23),
238			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
239
240			/* Make sure this isn't a fragment... */
241			BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
242			BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
243
244			/* Get the IP header length... */
245			BPF_STMT(BPF_LDX + BPF_B + BPF_MSH, 14),
246
247			/* Make sure it's from the right port... */
248			BPF_STMT(BPF_LD + BPF_H + BPF_IND, 14),
249			BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, SERVER_PORT, 0, 1),
250
251			/* If we passed all the tests, ask for the whole packet. */
252			BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
253
254			/* Otherwise, drop it. */
255			BPF_STMT(BPF_RET+BPF_K, 0),
256			};
257
258			int dhcp_bpf_wfilter_len = sizeof(dhcp_bpf_wfilter) / sizeof(struct bpf_insn);
259
260			void
261			if_register_receive(struct interface_info *info, int isserver)
262			{
263			struct bpf_version v;
264			struct bpf_program p;
265			int flag = 1, sz, cmplt = 0;
266
267			/* Open a BPF device and hang it on this interface... */
268			info->rfdesc = if_register_bpf(info);
269
270			/* Make sure the BPF version is in range... */
271			if (ioctl(info->rfdesc, BIOCVERSION, &v) == -1)
272			fatal("Can't get BPF version");
273
274			if (v.bv_major != BPF_MAJOR_VERSION \|\|
275			v.bv_minor < BPF_MINOR_VERSION)
276			fatalx("Kernel BPF version out of range - recompile dhcpd!");
277
278			/*
279			* Set immediate mode so that reads return as soon as a packet
280			* comes in, rather than waiting for the input buffer to fill
281			* with packets.
282			*/
283			if (ioctl(info->rfdesc, BIOCIMMEDIATE, &flag) == -1)
284			fatal("Can't set immediate mode on bpf device");
285
286			/* make sure kernel fills in the source ethernet address */
287			if (ioctl(info->rfdesc, BIOCSHDRCMPLT, &cmplt) == -1)
288			fatal("Can't set header complete flag on bpf device");
289
290			/* Get the required BPF buffer length from the kernel. */
291			if (ioctl(info->rfdesc, BIOCGBLEN, &sz) == -1)
292			fatal("Can't get bpf buffer length");
293			info->rbuf_max = sz;
294			info->rbuf = malloc(info->rbuf_max);
295			if (!info->rbuf)
296			fatalx("Can't allocate %lu bytes for bpf input buffer.",
297			(unsigned long)info->rbuf_max);
298			info->rbuf_offset = 0;
299			info->rbuf_len = 0;
300
301			/* Set up the bpf filter program structure. */
302			if (isserver) {
303			p.bf_len = dhcp_bpf_sfilter_len;
304			p.bf_insns = dhcp_bpf_sfilter;
305			} else if (info->hw_address.htype == HTYPE_IPSEC_TUNNEL) {
306			p.bf_len = dhcp_bpf_efilter_len;
307			p.bf_insns = dhcp_bpf_efilter;
308			} else {
309			p.bf_len = dhcp_bpf_filter_len;
310			p.bf_insns = dhcp_bpf_filter;
311			}
312			if (ioctl(info->rfdesc, BIOCSETF, &p) == -1)
313			fatal("Can't install packet filter program");
314
315			/* Set up the bpf write filter program structure. */
316			if (isserver) {
317			p.bf_len = dhcp_bpf_swfilter_len;
318			p.bf_insns = dhcp_bpf_swfilter;
319			} else {
320			p.bf_len = dhcp_bpf_wfilter_len;
321			p.bf_insns = dhcp_bpf_wfilter;
322			}
323
324			if (ioctl(info->rfdesc, BIOCSETWF, &p) == -1)
325			fatal("Can't install write filter program");
326
327			/* make sure these settings cannot be changed after dropping privs */
328			if (ioctl(info->rfdesc, BIOCLOCK) == -1)
329			fatal("Failed to lock bpf descriptor");
330			}
331
332			ssize_t
333			send_packet(struct interface_info *interface,
334			struct dhcp_packet raw, size_t len, struct packet_ctx pc)
335			{
336			unsigned char buf[256];
337			struct iovec iov[2];
338			ssize_t bufp;
339			int result;
340
341			result = -1;
342
343			if (interface->hw_address.htype == HTYPE_IPSEC_TUNNEL) {
344			socklen_t slen = pc->pc_dst.ss_len;
345			result = sendto(server_fd, raw, len, 0,
346			(struct sockaddr *)&pc->pc_dst, slen);
347			goto done;
348			}
349
350			/* Assemble the headers... */
351			if ((bufp = assemble_hw_header(buf, sizeof(buf), 0, pc,
352			interface->hw_address.htype)) == -1)
353			goto done;
354			if ((bufp = assemble_udp_ip_header(buf, sizeof(buf), bufp, pc,
355			(unsigned char *)raw, len)) == -1)
356			goto done;
357
358			/* Fire it off */
359			iov[0].iov_base = (char *)buf;
360			iov[0].iov_len = bufp;
361			iov[1].iov_base = (char *)raw;
362			iov[1].iov_len = len;
363
364			result = writev(interface->wfdesc, iov, 2);
365			done:
366			if (result == -1)
367			log_warn("send_packet");
368			return (result);
369			}
370
371			ssize_t
372			receive_packet(struct interface_info interface, unsigned char buf,
373			size_t len, struct packet_ctx *pc)
374			{
375			int length = 0;
376			ssize_t offset = 0;
377			struct bpf_hdr hdr;
378
379			/*
380			* All this complexity is because BPF doesn't guarantee that
381			* only one packet will be returned at a time. We're getting
382			* what we deserve, though - this is a terrible abuse of the BPF
383			* interface. Sigh.
384			*/
385
386			/* Process packets until we get one we can return or until we've
387			* done a read and gotten nothing we can return...
388			*/
389			do {
390			/* If the buffer is empty, fill it. */
391			if (interface->rbuf_offset == interface->rbuf_len) {
392			length = read(interface->rfdesc, interface->rbuf,
393			interface->rbuf_max);
394			if (length <= 0)
395			return (length);
396			interface->rbuf_offset = 0;
397			interface->rbuf_len = length;
398			}
399
400			/*
401			* If there isn't room for a whole bpf header, something
402			* went wrong, but we'll ignore it and hope it goes
403			* away... XXX
404			*/
405			if (interface->rbuf_len - interface->rbuf_offset <
406			sizeof(hdr)) {
407			interface->rbuf_offset = interface->rbuf_len;
408			continue;
409			}
410
411			/* Copy out a bpf header... */
412			memcpy(&hdr, &interface->rbuf[interface->rbuf_offset],
413			sizeof(hdr));
414
415			/*
416			* If the bpf header plus data doesn't fit in what's
417			* left of the buffer, stick head in sand yet again...
418			*/
419			if (interface->rbuf_offset + hdr.bh_hdrlen + hdr.bh_caplen >
420			interface->rbuf_len) {
421			interface->rbuf_offset = interface->rbuf_len;
422			continue;
423			}
424
425			/*
426			* If the captured data wasn't the whole packet, or if
427			* the packet won't fit in the input buffer, all we can
428			* do is drop it.
429			*/
430			if (hdr.bh_caplen != hdr.bh_datalen) {
431			interface->rbuf_offset += hdr.bh_hdrlen =
432			hdr.bh_caplen;
433			continue;
434			}
435
436			/* Skip over the BPF header... */
437			interface->rbuf_offset += hdr.bh_hdrlen;
438
439			/* Decode the physical header... */
440			offset = decode_hw_header(interface->rbuf,
441			interface->rbuf_len, interface->rbuf_offset, pc,
442			interface->hw_address.htype);
443
444			/*
445			* If decoding or a physical layer checksum failed
446			* (dunno of any physical layer that supports this, but WTH),
447			* skip this packet.
448			*/
449			if (offset < 0) {
450			interface->rbuf_offset += hdr.bh_caplen;
451			continue;
452			}
453
454			/* Decode the IP and UDP headers... */
455			offset = decode_udp_ip_header(interface->rbuf,
456			interface->rbuf_len, offset, pc);
457
458			/* If the IP or UDP checksum was bad, skip the packet... */
459			if (offset < 0) {
460			interface->rbuf_offset += hdr.bh_caplen;
461			continue;
462			}
463
464			hdr.bh_caplen -= offset - interface->rbuf_offset;
465			interface->rbuf_offset = offset;
466
467			/*
468			* If there's not enough room to stash the packet data,
469			* we have to skip it (this shouldn't happen in real
470			* life, though).
471			*/
472			if (hdr.bh_caplen > len) {
473			interface->rbuf_offset += hdr.bh_caplen;
474			continue;
475			}
476
477			/* Copy out the data in the packet... */
478			memcpy(buf, interface->rbuf + interface->rbuf_offset,
479			hdr.bh_caplen);
480			interface->rbuf_offset += hdr.bh_caplen;
481			return (hdr.bh_caplen);
482			} while (!length);
483			return (0);
484			}