chunk: Add function to calculate Internet Checksums according to RFC 1071

2014-07-22 11:10:35 +02:00
parent a10eb93566
commit b557f4a7cd
3 changed files with 105 additions and 0 deletions
@@ -987,6 +987,37 @@ u_int32_t chunk_hash_static(chunk_t chunk)
 	return chunk_mac(chunk, static_key);
 }

+/**
+ * Described in header.
+ */
+u_int16_t chunk_internet_checksum_inc(chunk_t data, u_int16_t checksum)
+{
+	u_int32_t sum = ntohs(~checksum);
+
+	while (data.len > 1)
+	{
+		sum += untoh16(data.ptr);
+		data = chunk_skip(data, 2);
+	}
+	if (data.len)
+	{
+		sum += (u_int16_t)*data.ptr << 8;
+	}
+	while (sum >> 16)
+	{
+		sum = (sum & 0xffff) + (sum >> 16);
+	}
+	return htons(~sum);
+}
+
+/**
+ * Described in header.
+ */
+u_int16_t chunk_internet_checksum(chunk_t data)
+{
+	return chunk_internet_checksum_inc(data, 0xffff);
+}
+
 /**
 * Described in header.
 */