1 files changed, 85 insertions, 0 deletions
diff --git a/net/checksum.c b/net/checksum.c
new file mode 100644
index 0000000000..4046932e9d
--- /dev/null
+++ b/net/checksum.c
@@ -0,0 +1,85 @@
+/*
+ *  IP checksumming functions.
+ *  (c) 2008 Gerd Hoffmann <kraxel@redhat.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; under version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "net/checksum.h"
+
+#define PROTO_TCP  6
+#define PROTO_UDP 17
+
+uint32_t net_checksum_add(int len, uint8_t *buf)
+{
+    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;
+    }
+    return sum;
+}
+
+uint16_t net_checksum_finish(uint32_t sum)
+{
+    while (sum>>16)
+	sum = (sum & 0xFFFF)+(sum >> 16);
+    return ~sum;
+}
+
+uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
+                             uint8_t *addrs, uint8_t *buf)
+{
+    uint32_t sum = 0;
+
+    sum += net_checksum_add(length, buf);         // payload
+    sum += net_checksum_add(8, addrs);            // src + dst address
+    sum += proto + length;                        // protocol & length
+    return net_checksum_finish(sum);
+}
+
+void net_checksum_calculate(uint8_t *data, int length)
+{
+    int hlen, plen, proto, csum_offset;
+    uint16_t csum;
+
+    if ((data[14] & 0xf0) != 0x40)
+	return; /* not IPv4 */
+    hlen  = (data[14] & 0x0f) * 4;
+    plen  = (data[16] << 8 | data[17]) - hlen;
+    proto = data[23];
+
+    switch (proto) {
+    case PROTO_TCP:
+	csum_offset = 16;
+	break;
+    case PROTO_UDP:
+	csum_offset = 6;
+	break;
+    default:
+	return;
+    }
+
+    if (plen < csum_offset+2)
+	return;
+
+    data[14+hlen+csum_offset]   = 0;
+    data[14+hlen+csum_offset+1] = 0;
+    csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen);
+    data[14+hlen+csum_offset]   = csum >> 8;
+    data[14+hlen+csum_offset+1] = csum & 0xff;
+}