Simplify in_cksum() and squelch one more warning.

sn_packets.c:66:32: warning: passing argument 1 of 'in_cksum' from
  incompatible pointer type [-Wincompatible-pointer-types]

Packet data comes as a sequence of bytes rather than 16-bit words, so
take is as bytes and reconstruct the words as necessary.  Also replace
host byte order pointer type casting with explicit network byte order in
the words.  Lose a few variables as well.  Drop "register" because it no
longer is necessary with modern compilers and it certainly has nothing
to do with endianness.  This function may have other problems, which
should be easier to see and to fix now.  Use unsigned char in a few
places to match the new prototype.

Author: infrastation

src/sn_generation.c

@@ -211,7 +211,7 @@ sp_help_ip->TTL = 69;
 sp_help_ip->protocol = proto;
 sp_help_ip->source = sp->source;
 sp_help_ip->destination =  sp->dest;
-sp_help_ip->checksum=in_cksum((unsigned short *) (sp->buffer),
+sp_help_ip->checksum=in_cksum(sp->buffer,
 						SP_IP_HEAD_BASE+sp->IP_optlen);
 #ifdef DEBUG
 	printf("IP header fixed...\n");
@@ -220,7 +220,7 @@ sp_help_ip->checksum=in_cksum((unsigned short *) (sp->buffer),
 
 static void sp_fix_TCP_packet (struct sp_data_exchange *sp)
 {
-char sp_pseudo_ip_construct[MTU];
+unsigned char sp_pseudo_ip_construct[MTU];
 struct TCP_header *sp_help_tcp;
 struct pseudo_IP_header *sp_help_pseudo;
 int i;
@@ -245,7 +245,7 @@ sp_help_pseudo->protocol = 6;
 sp_help_pseudo->TCP_UDP_len = htons(sp->datalen+SP_TCP_HEAD_BASE+sp->TCP_optlen);
 
 memcpy(sp_pseudo_ip_construct+12, sp_help_tcp, sp->TCP_optlen+sp->datalen+SP_TCP_HEAD_BASE);
-sp_help_tcp->checksum=in_cksum((unsigned short *) sp_pseudo_ip_construct,
+sp_help_tcp->checksum=in_cksum(sp_pseudo_ip_construct,
 				  sp->datalen+12+SP_TCP_HEAD_BASE+sp->TCP_optlen);
 #ifdef DEBUG
 	printf("TCP header fixed...\n");
@@ -260,7 +260,7 @@ static void transmit_TCP (int sp_fd, char *sp_data,
                            _32_bit sp_seq, _32_bit sp_ack,
                            unsigned short sp_flags)
 {
-char sp_buffer[1500];
+unsigned char sp_buffer[1500];
 struct sp_data_exchange sp_struct;
 
 bzero(sp_buffer,1500);
@@ -295,7 +295,7 @@ sp_send_packet(&sp_struct, 6);
 
 static void sp_fix_UDP_packet (struct sp_data_exchange *sp)
 {
-char sp_pseudo_ip_construct[MTU];
+unsigned char sp_pseudo_ip_construct[MTU];
 struct UDP_header *sp_help_udp;
 struct pseudo_IP_header *sp_help_pseudo;
 int i;
@@ -317,7 +317,7 @@ sp_help_pseudo->protocol = 17;
 sp_help_pseudo->TCP_UDP_len = htons(sp->datalen+SP_UDP_HEAD_BASE);
 
 memcpy(sp_pseudo_ip_construct+12, sp_help_udp, sp->datalen+SP_UDP_HEAD_BASE);
-sp_help_udp->checksum=in_cksum((unsigned short *) sp_pseudo_ip_construct,
+sp_help_udp->checksum=in_cksum(sp_pseudo_ip_construct,
 						     sp->datalen+12+SP_UDP_HEAD_BASE);
 #ifdef DEBUG
 	printf("UDP header fixed...\n");
@@ -329,7 +329,7 @@ static void transmit_UDP (int sp_fd, char *sp_data,
 		           _32_bit sp_source, unsigned short sp_source_port,
 			   _32_bit sp_dest, unsigned short sp_dest_port)
 {
-char sp_buffer[1500];
+unsigned char sp_buffer[1500];
 struct sp_data_exchange sp_struct;
 bzero(sp_buffer,1500);
 

src/sn_packets.c

@@ -11,29 +11,23 @@ extern int PROTO_HEAD;
 extern char NO_CHKSUM;
 
 /* This routine stolen from ping.c */
-unsigned short in_cksum(unsigned short *addr,int len)
+unsigned short in_cksum(const unsigned char *addr,int nleft)
 {
-register int nleft = len;   /* leave this alone.. my opinion is that the   */
-register unsigned short *w = addr;
-                            /* register is needed to make it work for both */
-register int sum = 0;       /* BIG and LITTLE endian machines              */
-unsigned short answer = 0;
-                        /* but then again, who am I to make such statement */
+int sum = 0;
 
 while (nleft > 1)
         {
-        sum += *w++;
+        sum += *addr++ << 8;
+        sum += *addr++;
         nleft -= 2;
         }
 if (nleft == 1)
         {
-        *(unsigned char *)(&answer) = *(unsigned char *)w ;
-        sum += answer;
+        sum += *addr++;
         }
 sum = (sum >> 16) + (sum & 0xffff);
 sum += (sum >> 16);
-answer = ~sum;
-return(answer);
+return(~sum);
 }
 
 int unwrap_packet (unsigned char *sp, struct unwrap *unwrapped)

src/sn_packets.h

@@ -3,7 +3,7 @@
 #ifndef _SN_PACKETS_H_
 #define _SN_PACKETS_H_
 
-extern unsigned short in_cksum(unsigned short *,int);
+extern unsigned short in_cksum(const unsigned char *,int);
 extern int unwrap_packet (const unsigned char *, struct unwrap *);
 
 #endif

src/sn_structs.h

@@ -86,7 +86,7 @@ struct sp_data_exchange {
         _32_bit dest;   unsigned short dest_port;
         _32_bit seq, ack;
         unsigned short flags;
-        char *buffer;               /* work buffer */
+        unsigned char *buffer;     /* work buffer */
         int IP_optlen;             /* IP options length in bytes  */
         int TCP_optlen;            /* TCP options length in bytes */
         };