X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=lib%2Fcsum.c;h=922f686257594caf2e7f7af3d03b0d9c485b8c02;hb=87eeed4c03ebb0847c093eeb8a6b7af5f2fd33af;hp=5266be6de252d63ca3255cad6907f92c1795504d;hpb=064af42167bf4fc9aaea2702d80ce08074b889c0;p=openvswitch

diff --git a/lib/csum.c b/lib/csum.c
index 5266be6d..922f6862 100644
--- a/lib/csum.c
+++ b/lib/csum.c
@@ -1,23 +1,28 @@
 /*
- * Copyright (c) 2008 Nicira Networks.
+ * Copyright (c) 2008, 2009 Nicira Networks.
  *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
  *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
- * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
- * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
- * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
 #include <config.h>
 #include "csum.h"
 
-/* Returns the IP checksum of the 'n' bytes in 'data'. */
+/* Returns the IP checksum of the 'n' bytes in 'data'.
+ *
+ * The return value has the same endianness as the data.  That is, if 'data'
+ * consists of a packet in network byte order, then the return value is a value
+ * in network byte order, and if 'data' consists of a data structure in host
+ * byte order, then the return value is in host byte order. */
 uint16_t
 csum(const void *data, size_t n)
 {
@@ -62,11 +67,19 @@ csum_continue(uint32_t partial, const void *data_, size_t n)
 }
 
 /* Returns the IP checksum corresponding to 'partial', which is a value updated
- * by some combination of csum_add16(), csum_add32(), and csum_continue(). */
+ * by some combination of csum_add16(), csum_add32(), and csum_continue().
+ *
+ * The return value has the same endianness as the checksummed data.  That is,
+ * if the data consist of a packet in network byte order, then the return value
+ * is a value in network byte order, and if the data are a data structure in
+ * host byte order, then the return value is in host byte order. */
 uint16_t
 csum_finish(uint32_t partial)
 {
-    return ~((partial & 0xffff) + (partial >> 16));
+    while (partial >> 16) {
+        partial = (partial & 0xffff) + (partial >> 16);
+    }
+    return ~partial;
 }
 
 /* Returns the new checksum for a packet in which the checksum field previously
@@ -83,8 +96,7 @@ recalc_csum16(uint16_t old_csum, uint16_t old_u16, uint16_t new_u16)
     uint16_t m_complement = ~old_u16;
     uint16_t m_prime = new_u16;
     uint32_t sum = hc_complement + m_complement + m_prime;
-    uint16_t hc_prime_complement = sum + (sum >> 16);
-    return ~hc_prime_complement;
+    return csum_finish(sum);
 }
 
 /* Returns the new checksum for a packet in which the checksum field previously