mirror of
https://gitlab.isc.org/isc-projects/dhcp
synced 2025-08-31 14:25:41 +00:00
Complete rewrite of Archie Cobbs' low-level packet assembly code; add packet disassembly code
This commit is contained in:
Ted Lemon
377
common/packet.c
377
common/packet.c
@@ -1,180 +1,253 @@
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/* packet.c
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static void IpChecksum(struct ip *ip);
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static void UdpChecksum(struct ip *ip);
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static u_int32_t Checksum(u_int16_t *buf, int nwords);
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Packet assembly code, originally contributed by Archie Cobbs. */
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struct raw_packet
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/*
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* Copyright (c) 1995, 1996 The Internet Software Consortium.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
|
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
|
||||
* notice, this list of conditions and the following disclaimer.
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||||
* 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.
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||||
* 3. Neither the name of The Internet Software Consortium nor the names
|
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* of its contributors may be used to endorse or promote products derived
|
||||
* from this software without specific prior written permission.
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||||
*
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||||
* 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,
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||||
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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||||
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This software has been written for the Internet Software Consortium
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* by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
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||||
* 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''.
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*/
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#ifndef lint
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static char copyright[] =
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"@(#) Copyright (c) 1996 The Internet Software Consortium. All rights reserved.\n";
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#endif /* not lint */
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#include "dhcpd.h"
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#include <sys/ioctl.h>
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#include <net/if_dl.h>
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#include <netinet/in_systm.h>
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#include <netinet/ip.h>
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#include <netinet/udp.h>
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#include <netinet/if_ether.h>
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static u_int32_t checksum PROTO ((unsigned char *, int, u_int32_t));
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static u_int32_t wrapsum PROTO ((u_int32_t));
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/* Assemble an hardware header... */
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/* XXX currently only supports ethernet; doesn't check for other types. */
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void assemble_hw_header (interface, buf, bufix, to)
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struct interface_info *interface;
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unsigned char *buf;
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int *bufix;
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struct hardware *to;
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{
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u_int16_t space;
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struct ether_header en_hdr;
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struct ip ip;
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struct udphdr udp;
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struct dhcp_packet dhcp;
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};
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struct ether_header eh;
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int sendpkt (in_packet, raw, len, to, tolen)
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struct packet *in_packet;
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struct dhcp_packet *raw;
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size_t len;
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struct sockaddr *to;
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int tolen;
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if (to)
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memcpy (eh.ether_dhost, to -> haddr, sizeof eh.ether_dhost);
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else
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memset (eh.ether_dhost, 0xff, sizeof (eh.ether_shost));
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if (interface -> hw_address.hlen == sizeof (eh.ether_shost))
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memcpy (eh.ether_shost, interface -> hw_address.haddr,
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sizeof (eh.ether_shost));
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else
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memset (eh.ether_shost, 0x00, sizeof (eh.ether_shost));
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eh.ether_type = htons (ETHERTYPE_IP);
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memcpy (&buf [*bufix], &eh, sizeof eh);
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*bufix += sizeof eh;
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}
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/* UDP header and IP header assembled together for convenience. */
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void assemble_udp_ip_header (interface, buf, bufix, addr, port, data, len)
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struct interface_info *interface;
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unsigned char *buf;
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int *bufix;
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u_int32_t addr;
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u_int16_t port;
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unsigned char *data;
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int len;
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{
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int i, k;
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struct iaddr dest;
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struct subnet *subnet;
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struct raw_packet out_packet;
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struct raw_packet *const pkt = &out_packet;
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struct ip ip;
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struct udphdr udp;
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/* Find local subnet, or else forward to gateway */
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/* Fill out the IP header */
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ip.ip_v = 4;
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ip.ip_hl = 5;
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ip.ip_tos = IPTOS_LOWDELAY;
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ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
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ip.ip_id = 0;
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ip.ip_off = 0;
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ip.ip_ttl = 16;
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ip.ip_p = IPPROTO_UDP;
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ip.ip_sum = 0;
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memcpy (&ip.ip_src, interface -> address.iabuf, 4);
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ip.ip_dst.s_addr = addr;
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/* Checksum the IP header... */
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ip.ip_sum = wrapsum (checksum ((unsigned char *)&ip, sizeof ip, 0));
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/* Copy the ip header into the buffer... */
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memcpy (&buf [*bufix], &ip, sizeof ip);
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*bufix += sizeof ip;
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dest.len = 4;
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memcpy(&dest.iabuf, &((struct sockaddr_in *) to)->sin_addr, dest.len);
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if ((subnet = find_subnet(dest)) == NULL)
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return(sendto(in_packet->client_sock, raw, len, 0, to, tolen));
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/* Fill out the UDP header */
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udp.uh_sport = htons (67); /* XXX */
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udp.uh_dport = port; /* XXX */
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udp.uh_ulen = htons(sizeof(udp) + len);
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memset (&udp.uh_sum, 0, sizeof udp.uh_sum);
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/* Find interface corresponding to subnet */
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/* Compute UDP checksums, including the ``pseudo-header'', the UDP
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header and the data. */
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for (i = 0; i < num_ifaces; i++)
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{
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for (k = 0; k < subnet->net.len
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&& (dest.iabuf[k] & subnet->netmask.iabuf[k])
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== (subnet->net.iabuf[k] & subnet->netmask.iabuf[k]);
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k++);
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if (k == subnet->net.len)
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break;
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udp.uh_sum =
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wrapsum (checksum ((unsigned char *)&udp, sizeof udp,
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checksum (data, len,
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checksum ((unsigned char *)
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&ip.ip_src,
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sizeof ip.ip_src,
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IPPROTO_UDP +
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(u_int32_t)
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ntohs (udp.uh_ulen)))));
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/* Copy the udp header into the buffer... */
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memcpy (&buf [*bufix], &udp, sizeof udp);
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*bufix += sizeof udp;
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}
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/* Decode a hardware header... */
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/* XXX currently only supports ethernet; doesn't check for other types. */
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size_t decode_hw_header (interface, buf, bufix, from)
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struct interface_info *interface;
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unsigned char *buf;
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int bufix;
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struct hardware *from;
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{
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struct ether_header eh;
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memcpy (&eh, buf +bufix, sizeof eh);
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memcpy (from -> haddr, eh.ether_shost, sizeof (eh.ether_shost));
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from -> htype = ETHERTYPE_IP;
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from -> hlen = sizeof eh.ether_shost;
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return sizeof eh;
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}
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/* UDP header and IP header decoded together for convenience. */
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size_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
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struct interface_info *interface;
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unsigned char *buf;
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int bufix;
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struct sockaddr_in *from;
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unsigned char *data;
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int len;
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{
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struct ip *ip;
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struct udphdr *udp;
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u_int32_t ip_len = (buf [bufix] & 0xf) << 2;
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u_int32_t sum, usum;
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/* Check the IP header checksum - it should be zero. */
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if (wrapsum (checksum (buf + bufix, ip_len, 0))) {
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note ("Bad IP checksum: %x",
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wrapsum (checksum (buf + bufix, sizeof ip, 0)));
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}
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if (i == num_ifaces)
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return(sendto(in_packet->client_sock, raw, len, 0, to, tolen));
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/* EtherNet header */
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/* Copy out the IP source address... */
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ip = (struct ip *)(buf + bufix);
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memcpy (&from -> sin_addr, &ip -> ip_src, 4);
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memset(pkt->en_hdr.ether_dhost, 0xff, sizeof(pkt->en_hdr.ether_dhost));
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memset(pkt->en_hdr.ether_shost, 0x00, sizeof(pkt->en_hdr.ether_shost));
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pkt->en_hdr.ether_type = ETHERTYPE_IP;
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/* Compute UDP checksums, including the ``pseudo-header'', the UDP
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header and the data. If the UDP checksum field is zero, we're
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not supposed to do a checksum. */
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/* IP header (except for checksum) */
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udp = (struct udphdr *)(buf + bufix + ip_len);
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if (!data) {
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data = buf + bufix + ip_len + sizeof *udp;
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len -= ip_len + sizeof *udp;
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}
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pkt->ip.ip_v = 4;
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pkt->ip.ip_hl = 5;
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pkt->ip.ip_tos = IPTOS_LOWDELAY;
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pkt->ip.ip_len = htons(sizeof(pkt->ip) + sizeof(pkt->udp) + len);
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pkt->ip.ip_id = 0;
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pkt->ip.ip_off = 0;
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pkt->ip.ip_ttl = 16;
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pkt->ip.ip_p = IPPROTO_UDP;
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pkt->ip.ip_sum = 0;
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pkt->ip.ip_src = if_list[i].address;
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inet_aton("255.255.255.255", &pkt->ip.ip_dst);
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usum = udp -> uh_sum;
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udp -> uh_sum = 0;
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sum = wrapsum (checksum ((unsigned char *)udp, sizeof *udp,
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checksum (data, len,
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checksum ((unsigned char *)
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&ip -> ip_src,
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sizeof ip -> ip_src,
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IPPROTO_UDP +
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(u_int32_t)
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ntohs (udp -> uh_ulen)))));
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/* UDP header */
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if (usum && usum != sum) {
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note ("Bad udp checksum: %x %x", usum, sum);
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return -1;
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}
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pkt->udp.uh_sport = htons(67); /* XXX! */
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pkt->udp.uh_dport = in_packet->client_port;
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pkt->udp.uh_ulen = htons(sizeof(pkt->udp) + len);
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pkt->udp.uh_sum = 0;
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/* Copy out the port... */
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memcpy (&from -> sin_port, &udp -> uh_sport, sizeof udp -> uh_sport);
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/* DHCP packet */
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pkt->dhcp = *raw;
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/* Compute checksums */
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UdpChecksum(&pkt->ip);
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IpChecksum(&pkt->ip);
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/* Fire it off */
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if (write(if_list[i].bpf, &pkt->en_hdr,
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ntohs(pkt->ip.ip_len) + sizeof(pkt->en_hdr)) < 0)
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warn ("Can't deliver packet: write: %m");
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return(0);
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return ip_len + sizeof *udp;
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}
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/*
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* UdpChecksum()
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*
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* Recompute a UDP checksum on a packet
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*
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* UDP pseudo-header (prot = IPPROTO_UDP = 17):
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*
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* | source IP address |
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* | dest. IP address |
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* | zero | prot | UDP leng |
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*
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*/
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/* Compute the easy part of the checksum on a range of bytes. */
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static void
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UdpChecksum(struct ip *ip)
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static u_int32_t checksum (unsigned char *buf, int nbytes, u_int32_t sum)
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{
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struct udphdr *udp = (struct udphdr *) ((long *) ip + ip->ip_hl);
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u_int32_t sum;
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int i;
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/* Pad with zero */
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if (ntohs(udp->uh_ulen) & 0x1)
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*((u_char *) udp + ntohs(udp->uh_ulen)) = 0;
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/* Do pseudo-header first */
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sum = Checksum((u_int16_t *) &ip->ip_src, 4);
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sum += (u_int16_t) IPPROTO_UDP;
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sum += (u_int16_t) ntohs(udp->uh_ulen);
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/* Now do UDP packet itself */
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udp->uh_sum = 0;
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sum += Checksum((u_int16_t *) udp,
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((u_int16_t) ntohs(udp->uh_ulen) + 1) >> 1);
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/* Flip it & stick it */
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sum = (sum >> 16) + (sum & 0xFFFF);
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sum += (sum >> 16);
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sum = ~sum;
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udp->uh_sum = htons(sum);
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/* Checksum all the pairs of bytes first... */
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for (i = 0; i < (nbytes & ~1); i += 2)
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sum += (u_int16_t) ntohs(*((u_int16_t *)buf)++);
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/* If there's a single byte left over, checksum it, too. Network
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byte order is big-endian, so the remaining byte is the high byte. */
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if (i < nbytes) {
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sum += (*buf) << 8;
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}
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return sum;
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}
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|
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/*
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* IpChecksum()
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*
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* Recompute an IP header checksum
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*
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*/
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/* Fold the upper sixteen bits of the checksum down into the lower bits,
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complement the sum, and then put it into network byte order. */
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static void
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IpChecksum(struct ip *ip)
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static u_int32_t wrapsum (u_int32_t sum)
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{
|
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u_int32_t sum;
|
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|
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/* Sum up IP header words */
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ip->ip_sum = 0;
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sum = Checksum((u_int16_t *) ip, ip->ip_hl * 2);
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/* Flip it & stick it */
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sum = (sum >> 16) + (sum & 0xFFFF);
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sum += (sum >> 16);
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sum = ~sum;
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ip->ip_sum = htons(sum);
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}
|
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|
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/*
|
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* Checksum()
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*
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* Do the one's complement sum thing over a range of words
|
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* Ideally, this should get replaced by an assembly version.
|
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*/
|
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|
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static u_int32_t
|
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Checksum(u_int16_t *buf, int nwords)
|
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{
|
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u_int32_t sum = 0;
|
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|
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while (nwords--)
|
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sum += (u_int16_t) ntohs(*buf++);
|
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return(sum);
|
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while (sum > 0x10000) {
|
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sum = (sum >> 16) + (sum & 0xFFFF);
|
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sum += (sum >> 16);
|
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}
|
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sum = ~sum;
|
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|
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return htons(sum);
|
||||
}
|
||||
|
||||
|
||||
377
packet.c
377
packet.c
@@ -1,180 +1,253 @@
|
||||
/* packet.c
|
||||
|
||||
static void IpChecksum(struct ip *ip);
|
||||
static void UdpChecksum(struct ip *ip);
|
||||
static u_int32_t Checksum(u_int16_t *buf, int nwords);
|
||||
Packet assembly code, originally contributed by Archie Cobbs. */
|
||||
|
||||
struct raw_packet
|
||||
/*
|
||||
* 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[] =
|
||||
"@(#) Copyright (c) 1996 The Internet Software Consortium. All rights reserved.\n";
|
||||
#endif /* not lint */
|
||||
|
||||
#include "dhcpd.h"
|
||||
#include <sys/ioctl.h>
|
||||
|
||||
#include <net/if_dl.h>
|
||||
#include <netinet/in_systm.h>
|
||||
#include <netinet/ip.h>
|
||||
#include <netinet/udp.h>
|
||||
#include <netinet/if_ether.h>
|
||||
|
||||
static u_int32_t checksum PROTO ((unsigned char *, int, u_int32_t));
|
||||
static u_int32_t wrapsum PROTO ((u_int32_t));
|
||||
|
||||
/* 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;
|
||||
{
|
||||
u_int16_t space;
|
||||
struct ether_header en_hdr;
|
||||
struct ip ip;
|
||||
struct udphdr udp;
|
||||
struct dhcp_packet dhcp;
|
||||
};
|
||||
struct ether_header eh;
|
||||
|
||||
int sendpkt (in_packet, raw, len, to, tolen)
|
||||
struct packet *in_packet;
|
||||
struct dhcp_packet *raw;
|
||||
size_t len;
|
||||
struct sockaddr *to;
|
||||
int tolen;
|
||||
if (to)
|
||||
memcpy (eh.ether_dhost, to -> haddr, sizeof eh.ether_dhost);
|
||||
else
|
||||
memset (eh.ether_dhost, 0xff, sizeof (eh.ether_shost));
|
||||
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));
|
||||
eh.ether_type = htons (ETHERTYPE_IP);
|
||||
|
||||
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, addr, port, data, len)
|
||||
struct interface_info *interface;
|
||||
unsigned char *buf;
|
||||
int *bufix;
|
||||
u_int32_t addr;
|
||||
u_int16_t port;
|
||||
unsigned char *data;
|
||||
int len;
|
||||
{
|
||||
int i, k;
|
||||
struct iaddr dest;
|
||||
struct subnet *subnet;
|
||||
struct raw_packet out_packet;
|
||||
struct raw_packet *const pkt = &out_packet;
|
||||
struct ip ip;
|
||||
struct udphdr udp;
|
||||
|
||||
/* Find local subnet, or else forward to gateway */
|
||||
/* 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;
|
||||
memcpy (&ip.ip_src, interface -> address.iabuf, 4);
|
||||
ip.ip_dst.s_addr = addr;
|
||||
|
||||
/* 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;
|
||||
|
||||
dest.len = 4;
|
||||
memcpy(&dest.iabuf, &((struct sockaddr_in *) to)->sin_addr, dest.len);
|
||||
if ((subnet = find_subnet(dest)) == NULL)
|
||||
return(sendto(in_packet->client_sock, raw, len, 0, to, tolen));
|
||||
/* Fill out the UDP header */
|
||||
udp.uh_sport = htons (67); /* XXX */
|
||||
udp.uh_dport = port; /* XXX */
|
||||
udp.uh_ulen = htons(sizeof(udp) + len);
|
||||
memset (&udp.uh_sum, 0, sizeof udp.uh_sum);
|
||||
|
||||
/* Find interface corresponding to subnet */
|
||||
/* Compute UDP checksums, including the ``pseudo-header'', the UDP
|
||||
header and the data. */
|
||||
|
||||
for (i = 0; i < num_ifaces; i++)
|
||||
{
|
||||
for (k = 0; k < subnet->net.len
|
||||
&& (dest.iabuf[k] & subnet->netmask.iabuf[k])
|
||||
== (subnet->net.iabuf[k] & subnet->netmask.iabuf[k]);
|
||||
k++);
|
||||
if (k == subnet->net.len)
|
||||
break;
|
||||
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)))));
|
||||
|
||||
/* Copy the udp header into the buffer... */
|
||||
memcpy (&buf [*bufix], &udp, sizeof udp);
|
||||
*bufix += sizeof udp;
|
||||
}
|
||||
|
||||
/* 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);
|
||||
|
||||
memcpy (from -> haddr, eh.ether_shost, sizeof (eh.ether_shost));
|
||||
from -> htype = ETHERTYPE_IP;
|
||||
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;
|
||||
|
||||
/* 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)));
|
||||
}
|
||||
if (i == num_ifaces)
|
||||
return(sendto(in_packet->client_sock, raw, len, 0, to, tolen));
|
||||
|
||||
/* EtherNet header */
|
||||
/* Copy out the IP source address... */
|
||||
ip = (struct ip *)(buf + bufix);
|
||||
memcpy (&from -> sin_addr, &ip -> ip_src, 4);
|
||||
|
||||
memset(pkt->en_hdr.ether_dhost, 0xff, sizeof(pkt->en_hdr.ether_dhost));
|
||||
memset(pkt->en_hdr.ether_shost, 0x00, sizeof(pkt->en_hdr.ether_shost));
|
||||
pkt->en_hdr.ether_type = ETHERTYPE_IP;
|
||||
/* 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. */
|
||||
|
||||
/* IP header (except for checksum) */
|
||||
udp = (struct udphdr *)(buf + bufix + ip_len);
|
||||
if (!data) {
|
||||
data = buf + bufix + ip_len + sizeof *udp;
|
||||
len -= ip_len + sizeof *udp;
|
||||
}
|
||||
|
||||
pkt->ip.ip_v = 4;
|
||||
pkt->ip.ip_hl = 5;
|
||||
pkt->ip.ip_tos = IPTOS_LOWDELAY;
|
||||
pkt->ip.ip_len = htons(sizeof(pkt->ip) + sizeof(pkt->udp) + len);
|
||||
pkt->ip.ip_id = 0;
|
||||
pkt->ip.ip_off = 0;
|
||||
pkt->ip.ip_ttl = 16;
|
||||
pkt->ip.ip_p = IPPROTO_UDP;
|
||||
pkt->ip.ip_sum = 0;
|
||||
pkt->ip.ip_src = if_list[i].address;
|
||||
inet_aton("255.255.255.255", &pkt->ip.ip_dst);
|
||||
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)))));
|
||||
|
||||
/* UDP header */
|
||||
if (usum && usum != sum) {
|
||||
note ("Bad udp checksum: %x %x", usum, sum);
|
||||
return -1;
|
||||
}
|
||||
|
||||
pkt->udp.uh_sport = htons(67); /* XXX! */
|
||||
pkt->udp.uh_dport = in_packet->client_port;
|
||||
pkt->udp.uh_ulen = htons(sizeof(pkt->udp) + len);
|
||||
pkt->udp.uh_sum = 0;
|
||||
/* Copy out the port... */
|
||||
memcpy (&from -> sin_port, &udp -> uh_sport, sizeof udp -> uh_sport);
|
||||
|
||||
/* DHCP packet */
|
||||
|
||||
pkt->dhcp = *raw;
|
||||
|
||||
/* Compute checksums */
|
||||
|
||||
UdpChecksum(&pkt->ip);
|
||||
IpChecksum(&pkt->ip);
|
||||
|
||||
/* Fire it off */
|
||||
|
||||
if (write(if_list[i].bpf, &pkt->en_hdr,
|
||||
ntohs(pkt->ip.ip_len) + sizeof(pkt->en_hdr)) < 0)
|
||||
warn ("Can't deliver packet: write: %m");
|
||||
return(0);
|
||||
return ip_len + sizeof *udp;
|
||||
}
|
||||
|
||||
/*
|
||||
* UdpChecksum()
|
||||
*
|
||||
* Recompute a UDP checksum on a packet
|
||||
*
|
||||
* UDP pseudo-header (prot = IPPROTO_UDP = 17):
|
||||
*
|
||||
* | source IP address |
|
||||
* | dest. IP address |
|
||||
* | zero | prot | UDP leng |
|
||||
*
|
||||
*/
|
||||
/* Compute the easy part of the checksum on a range of bytes. */
|
||||
|
||||
static void
|
||||
UdpChecksum(struct ip *ip)
|
||||
static u_int32_t checksum (unsigned char *buf, int nbytes, u_int32_t sum)
|
||||
{
|
||||
struct udphdr *udp = (struct udphdr *) ((long *) ip + ip->ip_hl);
|
||||
u_int32_t sum;
|
||||
int i;
|
||||
|
||||
/* Pad with zero */
|
||||
|
||||
if (ntohs(udp->uh_ulen) & 0x1)
|
||||
*((u_char *) udp + ntohs(udp->uh_ulen)) = 0;
|
||||
|
||||
/* Do pseudo-header first */
|
||||
|
||||
sum = Checksum((u_int16_t *) &ip->ip_src, 4);
|
||||
sum += (u_int16_t) IPPROTO_UDP;
|
||||
sum += (u_int16_t) ntohs(udp->uh_ulen);
|
||||
|
||||
/* Now do UDP packet itself */
|
||||
|
||||
udp->uh_sum = 0;
|
||||
sum += Checksum((u_int16_t *) udp,
|
||||
((u_int16_t) ntohs(udp->uh_ulen) + 1) >> 1);
|
||||
|
||||
/* Flip it & stick it */
|
||||
|
||||
sum = (sum >> 16) + (sum & 0xFFFF);
|
||||
sum += (sum >> 16);
|
||||
sum = ~sum;
|
||||
|
||||
udp->uh_sum = htons(sum);
|
||||
/* Checksum all the pairs of bytes first... */
|
||||
for (i = 0; i < (nbytes & ~1); i += 2)
|
||||
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) {
|
||||
sum += (*buf) << 8;
|
||||
}
|
||||
|
||||
return sum;
|
||||
}
|
||||
|
||||
/*
|
||||
* IpChecksum()
|
||||
*
|
||||
* Recompute an IP header checksum
|
||||
*
|
||||
*/
|
||||
/* 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 void
|
||||
IpChecksum(struct ip *ip)
|
||||
static u_int32_t wrapsum (u_int32_t sum)
|
||||
{
|
||||
u_int32_t sum;
|
||||
|
||||
/* Sum up IP header words */
|
||||
|
||||
ip->ip_sum = 0;
|
||||
sum = Checksum((u_int16_t *) ip, ip->ip_hl * 2);
|
||||
|
||||
/* Flip it & stick it */
|
||||
|
||||
sum = (sum >> 16) + (sum & 0xFFFF);
|
||||
sum += (sum >> 16);
|
||||
sum = ~sum;
|
||||
|
||||
ip->ip_sum = htons(sum);
|
||||
}
|
||||
|
||||
/*
|
||||
* Checksum()
|
||||
*
|
||||
* Do the one's complement sum thing over a range of words
|
||||
* Ideally, this should get replaced by an assembly version.
|
||||
*/
|
||||
|
||||
static u_int32_t
|
||||
Checksum(u_int16_t *buf, int nwords)
|
||||
{
|
||||
u_int32_t sum = 0;
|
||||
|
||||
while (nwords--)
|
||||
sum += (u_int16_t) ntohs(*buf++);
|
||||
return(sum);
|
||||
while (sum > 0x10000) {
|
||||
sum = (sum >> 16) + (sum & 0xFFFF);
|
||||
sum += (sum >> 16);
|
||||
}
|
||||
sum = ~sum;
|
||||
|
||||
return htons(sum);
|
||||
}
|
||||
|
||||
|
||||
Reference in New Issue
Block a user