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- /* $Id: checksum.c 1895 2007-08-22 04:24:33Z aturner $ */
- /*
- * Copyright (c) 2006 Aaron Turner.
- * Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com>
- * 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 names of the copyright owners 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 ``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 AUTHORS OR COPYRIGHT HOLDERS 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 code is heavily based on (some might even say stolen from) Mike Shiffman's
- * checksumming code from Libnet 1.1.3
- */
-
- #include "config.h"
- #include "tcpedit-int.h"
- #include "checksum.h"
- static int do_checksum_math(u_int16_t *, int);
- /**
- * Returns -1 on error and 0 on success, 1 on warn
- */
- int
- do_checksum(tcpedit_t *tcpedit, u_int8_t *data, int proto, int len) {
- ipv4_hdr_t *ipv4;
- ipv6_hdr_t *ipv6;
- tcp_hdr_t *tcp;
- udp_hdr_t *udp;
- icmpv4_hdr_t *icmp;
- int ip_hl;
- int sum;
-
- sum = 0;
- ipv4 = NULL;
- ipv6 = NULL;
- assert(data);
-
- if (len <= 0) {
- tcpedit_seterr(tcpedit, "%s", "length of data must be > 0");
- return TCPEDIT_ERROR;
- }
-
- ipv4 = (ipv4_hdr_t *)data;
- if (ipv4->ip_v == 6) {
- ipv6 = (ipv6_hdr_t *)data;
- ipv4 = NULL;
- ip_hl = 40;
- } else {
- ip_hl = ipv4->ip_hl << 2;
- }
-
- switch (proto) {
-
- case IPPROTO_TCP:
- tcp = (tcp_hdr_t *)(data + ip_hl);
- #ifdef STUPID_SOLARIS_CHECKSUM_BUG
- tcp->th_sum = tcp->th_off << 2;
- return (TCPEDIT_OK);
- #endif
- tcp->th_sum = 0;
-
- /* Note, we do both src & dst IP's at the same time, that's why the
- * length is 2x a single IP
- */
- if (ipv6 != NULL) {
- sum = do_checksum_math((u_int16_t *)&ipv6->ip_src, 32);
- } else {
- sum = do_checksum_math((u_int16_t *)&ipv4->ip_src, 8);
- }
- sum += ntohs(IPPROTO_TCP + len);
- sum += do_checksum_math((u_int16_t *)tcp, len);
- tcp->th_sum = CHECKSUM_CARRY(sum);
- break;
-
- case IPPROTO_UDP:
- udp = (udp_hdr_t *)(data + ip_hl);
- udp->uh_sum = 0;
- if (ipv6 != NULL) {
- sum = do_checksum_math((u_int16_t *)&ipv6->ip_src, 32);
- } else {
- sum = do_checksum_math((u_int16_t *)&ipv4->ip_src, 8);
- }
- sum += ntohs(IPPROTO_UDP + len);
- sum += do_checksum_math((u_int16_t *)udp, len);
- udp->uh_sum = CHECKSUM_CARRY(sum);
- break;
-
- case IPPROTO_ICMP:
- icmp = (icmpv4_hdr_t *)(data + ip_hl);
- icmp->icmp_sum = 0;
- if (ipv6 != NULL) {
- sum = do_checksum_math((u_int16_t *)&ipv6->ip_src, 32);
- icmp->icmp_sum = CHECKSUM_CARRY(sum);
- }
- sum += do_checksum_math((u_int16_t *)icmp, len);
- icmp->icmp_sum = CHECKSUM_CARRY(sum);
- break;
-
-
- case IPPROTO_IP:
- ipv4->ip_sum = 0;
- sum = do_checksum_math((u_int16_t *)data, ip_hl);
- ipv4->ip_sum = CHECKSUM_CARRY(sum);
- break;
-
-
- case IPPROTO_IGMP:
- case IPPROTO_GRE:
- case IPPROTO_OSPF:
- case IPPROTO_OSPF_LSA:
- case IPPROTO_VRRP:
- case TCPR_PROTO_CDP:
- case TCPR_PROTO_ISL:
- default:
- tcpedit_setwarn(tcpedit, "Unsupported protocol for checksum: 0x%x", proto);
- return TCPEDIT_WARN;
- }
-
- return TCPEDIT_OK;
- }
- /**
- * code to do a ones-compliment checksum
- */
- static int
- do_checksum_math(u_int16_t *data, int len)
- {
- int sum = 0;
- union {
- u_int16_t s;
- u_int8_t b[2];
- } pad;
-
- while (len > 1) {
- sum += *data++;
- len -= 2;
- }
-
- if (len == 1) {
- pad.b[0] = *(u_int8_t *)data;
- pad.b[1] = 0;
- sum += pad.s;
- }
-
- return (sum);
- }
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