+static uint16_t client_checksum(void *buf, int len)
+{
+ uint32_t sum;
+ uint16_t *check;
+ int i;
+ uint8_t *odd;
+
+ sum = 0;
+ check = buf;
+
+ for (i = 0; i < len / 2 ; i++)
+ sum += check[i];
+
+ if (len & 0x01) {
+ odd = buf;
+ sum += odd[len];
+ }
+
+ return ~((sum & 0xffff) + (sum >> 16));
+}
+
+static void test_checksum(void)
+{
+ uint8_t buf[20] = {
+ 0x45, 0x00, 0x02, 0x40, 0x00, 0x00, 0x00, 0x00,
+ 0x40, 0x11, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0xff, 0xff, 0xff, 0xff
+ };
+
+ uint8_t check[2] = {
+ 0x78, 0xae
+ };
+
+ uint16_t *val = (uint16_t *)check;
+
+ assert(client_checksum(&buf, 20) == *val);
+}
+