Checksum-related utility functions

net_checksum_add_cont()
checksum calculation for scattered data with odd chunk sizes

net_raw_checksum()
checksum calculation for a buffer
Signed-off-by: NDmitry Fleytman <dmitry@daynix.com>
Signed-off-by: NYan Vugenfirer <yan@daynix.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

include/net/checksum.h

@@ -20,10 +20,22 @@
 
 #include <stdint.h>
 
-uint32_t net_checksum_add(int len, uint8_t *buf);
+uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq);
 uint16_t net_checksum_finish(uint32_t sum);
 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
                              uint8_t *addrs, uint8_t *buf);
 void net_checksum_calculate(uint8_t *data, int length);
 
+static inline uint32_t
+net_checksum_add(int len, uint8_t *buf)
+{
+    return net_checksum_add_cont(len, buf, 0);
+}
+
+static inline uint16_t
+net_raw_checksum(uint8_t *data, int length)
+{
+    return net_checksum_finish(net_checksum_add(length, data));
+}
+
 #endif /* QEMU_NET_CHECKSUM_H */

net/checksum.c

@@ -20,16 +20,17 @@
 #define PROTO_TCP  6
 #define PROTO_UDP 17
 
-uint32_t net_checksum_add(int len, uint8_t *buf)
+uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
 {
     uint32_t sum = 0;
     int i;
 
-    for (i = 0; i < len; i++) {
-	if (i & 1)
-	    sum += (uint32_t)buf[i];
-	else
-	    sum += (uint32_t)buf[i] << 8;
+    for (i = seq; i < seq + len; i++) {
+        if (i & 1) {
+            sum += (uint32_t)buf[i - seq];
+        } else {
+            sum += (uint32_t)buf[i - seq] << 8;
+        }
     }
     return sum;
 }