zebra, lib: fix the ZEBRA_INTERFACE_VRF_UPDATE zapi message

[mirror_frr.git] / lib / checksum.c

diff --git a/lib/checksum.c b/lib/checksum.c
index 8c0ea521c9f1b36ee18efadfec7c864d037d7010..18e385047443ff829defdab2bb0ac528c1f5454d 100644 (file)
--- a/lib/checksum.c
+++ b/lib/checksum.c
@@ -7,13 +7,15 @@
  */
 
 #include <zebra.h>
+#include "checksum.h"
 
-int                            /* return checksum in low-order 16 bits */
-in_cksum(u_short *ptr, int nbytes)
+int /* return checksum in low-order 16 bits */
+       in_cksum(void *parg, int nbytes)
 {
-       register long           sum;            /* assumes long == 32 bits */
-       u_short                 oddbyte;
-       register u_short        answer;         /* assumes u_short == 16 bits */
+       unsigned short *ptr = parg;
+       register long sum; /* assumes long == 32 bits */
+       unsigned short oddbyte;
+       register unsigned short answer; /* assumes unsigned short == 16 bits */
 
        /*
         * Our algorithm is simple, using a 32-bit accumulator (sum),
@@ -22,15 +24,15 @@ in_cksum(u_short *ptr, int nbytes)
         */
 
        sum = 0;
-       while (nbytes > 1)  {
+       while (nbytes > 1) {
                sum += *ptr++;
                nbytes -= 2;
        }
 
-                               /* mop up an odd byte, if necessary */
+       /* mop up an odd byte, if necessary */
        if (nbytes == 1) {
-               oddbyte = 0;            /* make sure top half is zero */
-               *((u_char *) &oddbyte) = *(u_char *)ptr;   /* one byte only */
+               oddbyte = 0; /* make sure top half is zero */
+               *((uint8_t *)&oddbyte) = *(uint8_t *)ptr; /* one byte only */
                sum += oddbyte;
        }
 
@@ -38,8 +40,80 @@ in_cksum(u_short *ptr, int nbytes)
         * Add back carry outs from top 16 bits to low 16 bits.
         */
 
-       sum  = (sum >> 16) + (sum & 0xffff);    /* add high-16 to low-16 */
-       sum += (sum >> 16);                     /* add carry */
-       answer = ~sum;          /* ones-complement, then truncate to 16 bits */
-       return(answer);
+       sum = (sum >> 16) + (sum & 0xffff); /* add high-16 to low-16 */
+       sum += (sum >> 16);                 /* add carry */
+       answer = ~sum; /* ones-complement, then truncate to 16 bits */
+       return (answer);
+}
+
+/* Fletcher Checksum -- Refer to RFC1008. */
+#define MODX                 4102U   /* 5802 should be fine */
+
+/* To be consistent, offset is 0-based index, rather than the 1-based
+   index required in the specification ISO 8473, Annex C.1 */
+/* calling with offset == FLETCHER_CHECKSUM_VALIDATE will validate the checksum
+   without modifying the buffer; a valid checksum returns 0 */
+uint16_t fletcher_checksum(uint8_t *buffer, const size_t len,
+                          const uint16_t offset)
+{
+       uint8_t *p;
+       int x, y, c0, c1;
+       uint16_t checksum = 0;
+       uint16_t *csum;
+       size_t partial_len, i, left = len;
+
+       if (offset != FLETCHER_CHECKSUM_VALIDATE)
+       /* Zero the csum in the packet. */
+       {
+               assert(offset
+                      < (len - 1)); /* account for two bytes of checksum */
+               csum = (uint16_t *)(buffer + offset);
+               *(csum) = 0;
+       }
+
+       p = buffer;
+       c0 = 0;
+       c1 = 0;
+
+       while (left != 0) {
+               partial_len = MIN(left, MODX);
+
+               for (i = 0; i < partial_len; i++) {
+                       c0 = c0 + *(p++);
+                       c1 += c0;
+               }
+
+               c0 = c0 % 255;
+               c1 = c1 % 255;
+
+               left -= partial_len;
+       }
+
+       /* The cast is important, to ensure the mod is taken as a signed value.
+        */
+       x = (int)((len - offset - 1) * c0 - c1) % 255;
+
+       if (x <= 0)
+               x += 255;
+       y = 510 - c0 - x;
+       if (y > 255)
+               y -= 255;
+
+       if (offset == FLETCHER_CHECKSUM_VALIDATE) {
+               checksum = (c1 << 8) + c0;
+       } else {
+               /*
+                * Now we write this to the packet.
+                * We could skip this step too, since the checksum returned
+                * would
+                * be stored into the checksum field by the caller.
+                */
+               buffer[offset] = x;
+               buffer[offset + 1] = y;
+
+               /* Take care of the endian issue */
+               checksum = htons((x << 8) | (y & 0xFF));
+       }
+
+       return checksum;
 }