X-Git-Url: http://sjero.net/git/?p=ltp2tcp;a=blobdiff_plain;f=checksums.c;fp=checksums.c;h=ab295907ca750848a4501dee22ab13289e09bdd9;hp=0000000000000000000000000000000000000000;hb=1e87d36e278f025744a728a854a81c1a01fecc57;hpb=415ee2322fe2a27adcd10e5db2871699fc4f4f07

diff --git a/checksums.c b/checksums.c
new file mode 100644
index 0000000..ab29590
--- /dev/null
+++ b/checksums.c
@@ -0,0 +1,112 @@
+/******************************************************************************
+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));
+}