-/*
- * Fast checksum update for possibly oddly-aligned UDP byte, from the
- * code example in the draft.
- */
-static void fast_csum(unsigned char *csum,
- const unsigned char *optr,
- const unsigned char *nptr,
- int odd)
-{
- long x, old, new;
-
- x = csum[0] * 256 + csum[1];
-
- x =~ x & 0xFFFF;
-
- if (odd) old = optr[0] * 256;
- else old = optr[0];
-
- x -= old & 0xFFFF;
- if (x <= 0) {
- x--;
- x &= 0xFFFF;
- }
-
- if (odd) new = nptr[0] * 256;
- else new = nptr[0];
-
- x += new & 0xFFFF;
- if (x & 0x10000) {
- x++;
- x &= 0xFFFF;
- }
-
- x =~ x & 0xFFFF;
- csum[0] = x / 256;
- csum[1] = x & 0xFF;
-}
-
-/*
- * Mangle IP address.
- * - begin points to the start of the snmp messgae
- * - addr points to the start of the address
- */
-static inline void mangle_address(unsigned char *begin,
- unsigned char *addr,
- const struct oct1_map *map,
- u_int16_t *check)
-{
- if (map->from == NOCT1(*addr)) {
- u_int32_t old;
-
- if (debug)
- memcpy(&old, (unsigned char *)addr, sizeof(old));
-
- *addr = map->to;
-
- /* Update UDP checksum if being used */
- if (*check) {
- unsigned char odd = !((addr - begin) % 2);
-
- fast_csum((unsigned char *)check,
- &map->from, &map->to, odd);
-
- }
-
- if (debug)
- printk(KERN_DEBUG "bsalg: mapped %u.%u.%u.%u to "
- "%u.%u.%u.%u\n", NIPQUAD(old), NIPQUAD(*addr));
- }
-}
-