--- /dev/null
+/******************************************************************************
+IPv4 and IPv6 Header Checksum Code
+
+Copyright (C) 2013 Samuel Jero <sj323707@ohio.edu>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Author: Samuel Jero <sj323707@ohio.edu>
+Date: 02/2013
+******************************************************************************/
+#include <string.h>
+#include <arpa/inet.h>
+#include "checksums.h"
+
+/*Stupid Solaris*/
+#ifndef u_int32_t
+#define u_int32_t uint32_t
+#endif
+#ifndef u_int16_t
+#define u_int16_t uint16_t
+#endif
+
+//Pseudo Headers for checksums
+struct ip6_pseudo_hdr{
+ u_char src[IP6_ADDR_LEN];
+ u_char dest[IP6_ADDR_LEN];
+ unsigned int len;
+ u_char zero[3];
+ u_char nxt;
+};
+struct ip4_pseudo_hdr{
+ u_char src[IP4_ADDR_LEN];
+ u_char dest[IP4_ADDR_LEN];
+ unsigned int len;
+ u_char zero[3];
+ u_char nxt;
+};
+
+/*From http://gitorious.org/freebsd/freebsd/blobs/HEAD/sbin/dhclient/packet.c
+ * under GNU GPL*/
+u_int32_t checksum(u_char *buf, unsigned nbytes, u_int32_t sum)
+{
+ int i;
+ /* Checksum all the pairs of bytes first... */
+ for (i = 0; i < (nbytes & ~1U); i += 2) {
+ sum += (u_int16_t)ntohs(*((u_int16_t *)(buf + i)));
+ if (sum > 0xFFFF)
+ sum -= 0xFFFF;
+ }
+ /*
+ * 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[i] << 8;
+ if (sum > 0xFFFF)
+ sum -= 0xFFFF;
+ }
+ return (sum);
+}
+
+/*From http://gitorious.org/freebsd/freebsd/blobs/HEAD/sbin/dhclient/packet.c
+ * under GNU GPL*/
+u_int32_t wrapsum(u_int32_t sum)
+{
+ sum = ~sum & 0xFFFF;
+ return (htons(sum));
+}
+
+u_int16_t ipv6_pseudohdr_chksum(u_char* buff, int len, u_char* dest, u_char* src, int type){
+ struct ip6_pseudo_hdr hdr;
+
+ //create pseudo header
+ memset(&hdr, 0, sizeof(struct ip6_pseudo_hdr));
+ memcpy(hdr.src, src, IP6_ADDR_LEN);
+ memcpy(hdr.dest, dest, IP6_ADDR_LEN);
+ hdr.nxt=type;
+ hdr.len=htonl(len);
+
+ //calculate total checksum
+ return wrapsum(checksum((unsigned char*)&hdr,sizeof(struct ip6_pseudo_hdr),checksum(buff,len,0)));
+}
+
+u_int16_t ipv4_pseudohdr_chksum(u_char* buff, int len, u_char* dest, u_char* src, int type){
+ struct ip4_pseudo_hdr hdr;
+
+ //create pseudo header
+ memset(&hdr, 0, sizeof(struct ip4_pseudo_hdr));
+ memcpy(hdr.src, src, IP4_ADDR_LEN);
+ memcpy(hdr.dest, dest, IP4_ADDR_LEN);
+ hdr.nxt=type;
+ hdr.len=htonl(len);
+
+ //calculate total checksum
+ return wrapsum(checksum((u_char*)&hdr,sizeof(struct ip4_pseudo_hdr),checksum(buff,len,0)));
+}
+
+u_int16_t ipv4_chksum(u_char* buff, int len){
+ return wrapsum(checksum(buff,len,0));
+}