1 files changed, 37 insertions, 0 deletions
diff --git a/net/inet.c b/net/inet.c
new file mode 100644
index 0000000..f7cc2a6
--- /dev/null
+++ b/net/inet.c
@@ -0,0 +1,37 @@
+#include "inet.h"
+
+uint16_t ntohs(uint16_t val)
+{
+    return val<<8|val>>8;
+}
+uint16_t htons(uint16_t val)
+{
+    return val<<8|val>>8;
+}
+
+uint16_t checksum(void *addr, int count)
+{
+    /* Compute Internet Checksum for "count" bytes
+     *         beginning at location "addr".
+     * Taken from https://tools.ietf.org/html/rfc1071
+     */
+
+    register uint32_t sum = 0;
+    uint16_t * ptr = addr;
+
+    while( count > 1 )  {
+        /*  This is the inner loop */
+        sum += ntohs(* ptr++);
+        count -= 2;
+    }
+
+    /*  Add left-over byte, if any */
+    if( count > 0 )
+        sum += * (uint8_t *) ptr;
+
+    /*  Fold 32-bit sum to 16 bits */
+    while (sum>>16)
+        sum = (sum & 0xffff) + (sum >> 16);
+
+    return ~sum;
+}