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NetBSD/usr.sbin/dhcpd/packet.c

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/* packet.c
Packet assembly code, originally contributed by Archie Cobbs. */
/*
* Copyright (c) 1995, 1996 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''.
*/
#ifndef lint
static char copyright[] =
"$Id: packet.c,v 1.2 1996/10/03 06:57:21 mrg Exp $ Copyright (c) 1996 The Internet Software Consortium. All rights reserved.\n";
#endif /* not lint */
#include "dhcpd.h"
#if defined (PACKET_ASSEMBLY) || defined (PACKET_DECODING)
#include <netinet/in_systm.h>
#ifdef __NetBSD__
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <netinet/if_ether.h>
#else
#include "includes/netinet/ip.h"
#include "includes/netinet/udp.h"
#include "includes/netinet/if_ether.h"
#endif
static u_int32_t checksum PROTO ((unsigned char *, int, u_int32_t));
static u_int32_t wrapsum PROTO ((u_int32_t));
/* Compute the easy part of the checksum on a range of bytes. */
static u_int32_t checksum (buf, nbytes, sum)
unsigned char *buf;
int nbytes;
u_int32_t sum;
{
int i;
#ifdef DEBUG_CHECKSUM
debug ("checksum (%x %d %x)", buf, nbytes, sum);
#endif
/* Checksum all the pairs of bytes first... */
for (i = 0; i < (nbytes & ~1); i += 2) {
#ifdef DEBUG_CHECKSUM_VERBOSE
debug ("sum = %x", sum);
#endif
sum += (u_int16_t) ntohs(*((u_int16_t *)buf)++);
}
/* If there's a single byte left over, checksum it, too. Network
byte order is big-endian, so the remaining byte is the high byte. */
if (i < nbytes) {
#ifdef DEBUG_CHECKSUM_VERBOSE
debug ("sum = %x", sum);
#endif
sum += (*buf) << 8;
}
return sum;
}
/* Fold the upper sixteen bits of the checksum down into the lower bits,
complement the sum, and then put it into network byte order. */
static u_int32_t wrapsum (sum)
u_int32_t sum;
{
#ifdef DEBUG_CHECKSUM
debug ("wrapsum (%x)", sum);
#endif
while (sum > 0x10000) {
sum = (sum >> 16) + (sum & 0xFFFF);
#ifdef DEBUG_CHECKSUM_VERBOSE
debug ("sum = %x", sum);
#endif
sum += (sum >> 16);
#ifdef DEBUG_CHECKSUM_VERBOSE
debug ("sum = %x", sum);
#endif
}
sum = sum ^ 0xFFFF;
#ifdef DEBUG_CHECKSUM_VERBOSE
debug ("sum = %x", sum);
#endif
#ifdef DEBUG_CHECKSUM
debug ("wrapsum returns %x", htons (sum));
#endif
return htons(sum);
}
#endif /* PACKET_ASSEMBLY || PACKET_DECODING */
#ifdef PACKET_ASSEMBLY
/* Assemble an hardware header... */
/* XXX currently only supports ethernet; doesn't check for other types. */
void assemble_hw_header (interface, buf, bufix, to)
struct interface_info *interface;
unsigned char *buf;
int *bufix;
struct hardware *to;
{
struct ether_header eh;
if (to && to -> hlen == 6) /* XXX */
memcpy (eh.ether_dhost, to -> haddr, sizeof eh.ether_dhost);
else
memset (eh.ether_dhost, 0xff, sizeof (eh.ether_dhost));
if (interface -> hw_address.hlen == sizeof (eh.ether_shost))
memcpy (eh.ether_shost, interface -> hw_address.haddr,
sizeof (eh.ether_shost));
else
memset (eh.ether_shost, 0x00, sizeof (eh.ether_shost));
#ifdef BROKEN_FREEBSD_BPF /* Fixed in FreeBSD 2.2 */
eh.ether_type = ETHERTYPE_IP;
#else
eh.ether_type = htons (ETHERTYPE_IP);
#endif
memcpy (&buf [*bufix], &eh, sizeof eh);
*bufix += sizeof eh;
}
/* UDP header and IP header assembled together for convenience. */
void assemble_udp_ip_header (interface, buf, bufix,
from, to, port, data, len)
struct interface_info *interface;
unsigned char *buf;
int *bufix;
u_int32_t from;
u_int32_t to;
u_int16_t port;
unsigned char *data;
int len;
{
struct ip ip;
struct udphdr udp;
/* Fill out the IP header */
ip.ip_v = 4;
ip.ip_hl = 5;
ip.ip_tos = IPTOS_LOWDELAY;
ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
ip.ip_id = 0;
ip.ip_off = 0;
ip.ip_ttl = 16;
ip.ip_p = IPPROTO_UDP;
ip.ip_sum = 0;
ip.ip_src.s_addr = from;
ip.ip_dst.s_addr = to;
/* Checksum the IP header... */
ip.ip_sum = wrapsum (checksum ((unsigned char *)&ip, sizeof ip, 0));
/* Copy the ip header into the buffer... */
memcpy (&buf [*bufix], &ip, sizeof ip);
*bufix += sizeof ip;
/* Fill out the UDP header */
udp.uh_sport = server_port; /* XXX */
udp.uh_dport = port; /* XXX */
udp.uh_ulen = htons(sizeof(udp) + len);
memset (&udp.uh_sum, 0, sizeof udp.uh_sum);
/* Compute UDP checksums, including the ``pseudo-header'', the UDP
header and the data. */
#if 0
udp.uh_sum =
wrapsum (checksum ((unsigned char *)&udp, sizeof udp,
checksum (data, len,
checksum ((unsigned char *)
&ip.ip_src,
sizeof ip.ip_src,
IPPROTO_UDP +
(u_int32_t)
ntohs (udp.uh_ulen)))));
#endif
/* Copy the udp header into the buffer... */
memcpy (&buf [*bufix], &udp, sizeof udp);
*bufix += sizeof udp;
}
#endif /* PACKET_ASSEMBLY */
#ifdef PACKET_DECODING
/* Decode a hardware header... */
/* XXX currently only supports ethernet; doesn't check for other types. */
size_t decode_hw_header (interface, buf, bufix, from)
struct interface_info *interface;
unsigned char *buf;
int bufix;
struct hardware *from;
{
struct ether_header eh;
memcpy (&eh, buf + bufix, sizeof eh);
#ifdef USERLAND_FILTER
if (ntohs (eh.ether_type) != ETHERTYPE_IP)
return -1;
#endif
memcpy (from -> haddr, eh.ether_shost, sizeof (eh.ether_shost));
from -> htype = ARPHRD_ETHER;
from -> hlen = sizeof eh.ether_shost;
return sizeof eh;
}
/* UDP header and IP header decoded together for convenience. */
size_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
struct interface_info *interface;
unsigned char *buf;
int bufix;
struct sockaddr_in *from;
unsigned char *data;
int len;
{
struct ip *ip;
struct udphdr *udp;
u_int32_t ip_len = (buf [bufix] & 0xf) << 2;
u_int32_t sum, usum;
ip = (struct ip *)(buf + bufix);
udp = (struct udphdr *)(buf + bufix + ip_len);
#ifdef USERLAND_FILTER
/* Is it a UDP packet? */
if (ip -> ip_p != IPPROTO_UDP)
return -1;
/* Is it to the port we're serving? */
if (udp -> uh_dport != server_port)
return -1;
#endif /* USERLAND_FILTER */
/* Check the IP header checksum - it should be zero. */
if (wrapsum (checksum (buf + bufix, ip_len, 0))) {
note ("Bad IP checksum: %x",
wrapsum (checksum (buf + bufix, sizeof *ip, 0)));
return -1;
}
/* Copy out the IP source address... */
memcpy (&from -> sin_addr, &ip -> ip_src, 4);
/* Compute UDP checksums, including the ``pseudo-header'', the UDP
header and the data. If the UDP checksum field is zero, we're
not supposed to do a checksum. */
if (!data) {
data = buf + bufix + ip_len + sizeof *udp;
len -= ip_len + sizeof *udp;
}
#if 0
usum = udp -> uh_sum;
udp -> uh_sum = 0;
sum = wrapsum (checksum ((unsigned char *)udp, sizeof *udp,
checksum (data, len,
checksum ((unsigned char *)
&ip -> ip_src,
sizeof ip -> ip_src,
IPPROTO_UDP +
(u_int32_t)
ntohs (udp -> uh_ulen)))));
if (usum && usum != sum) {
note ("Bad udp checksum: %x %x", usum, sum);
return -1;
}
#endif
/* Copy out the port... */
memcpy (&from -> sin_port, &udp -> uh_sport, sizeof udp -> uh_sport);
return ip_len + sizeof *udp;
}
#endif /* PACKET_DECODING */
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