packet: move some common code out of wrapper.c and util.c

pass-1/util.c

@@ -52,43 +52,6 @@ int create_tun( const char* name )
     return fd;
 }
 
-
-// shamelessly copied from:
-// http://www.roman10.net/how-to-calculate-iptcpudp-checksumpart-2-implementation/
-unsigned short compute_checksum(unsigned short *addr, unsigned int count) {
-
-  unsigned long sum = 0;
-
-  while (count > 1) {
-    sum += * addr++;
-    count -= 2;
-  }
-
-  //if any bytes left, pad the bytes and add
-  if(count > 0) {
-    sum += ((*addr)&htons(0xFF00));
-  }
-
-  //Fold sum to 16 bits: add carrier to result
-  while (sum>>16) {
-      sum = (sum & 0xffff) + (sum >> 16);
-  }
-
-  //one's complement
-  sum = ~sum;
-
-  return ((unsigned short)sum);
-
-}
-
-void compute_ip_checksum(struct iphdr* pkt)
-{
-  pkt->check = 0x0000;
-  pkt->check = compute_checksum( (unsigned short*) pkt, pkt->ihl * 4 );
-}
-
-
-
 int link_set_up( char *link_name, int state )
 {
     int fd = socket( PF_INET, SOCK_DGRAM, IPPROTO_IP );