Added ethernet checksum reforging and nDPI protocol export in nDPI-extcap reader

1 files changed, 40 insertions, 0 deletions

diff --git a/example/ndpi_util.c b/example/ndpi_util.c
index 8fe80111a..cd3c8a1e3 100644
--- a/example/ndpi_util.c
+++ b/example/ndpi_util.c
@@ -909,3 +909,43 @@ struct ndpi_proto ndpi_workflow_process_packet (struct ndpi_workflow * workflow,
   return(packet_processing(workflow, time, vlan_id, iph, iph6,
 			   ip_offset, header->len - ip_offset, header->len));
 }
+
+/* ********************************************************** */
+/*       http://home.thep.lu.se/~bjorn/crc/crc32_fast.c       */
+/* ********************************************************** */
+
+static uint32_t crc32_for_byte(uint32_t r) {
+	for(int j = 0; j < 8; ++j)
+		r = (r & 1? 0: (uint32_t)0xEDB88320L) ^ r >> 1;
+	return r ^ (uint32_t)0xFF000000L;
+}
+
+/* Any unsigned integer type with at least 32 bits may be used as
+ * accumulator type for fast crc32-calulation, but unsigned long is
+ * probably the optimal choice for most systems. */
+typedef unsigned long accum_t;
+
+static void init_tables(uint32_t* table, uint32_t* wtable) {
+	for(size_t i = 0; i < 0x100; ++i)
+		table[i] = crc32_for_byte(i);
+	for(size_t k = 0; k < sizeof(accum_t); ++k)
+		for(size_t w, i = 0; i < 0x100; ++i) {
+			for(size_t j = w = 0; j < sizeof(accum_t); ++j)
+				w = table[(uint8_t)(j == k? w ^ i: w)] ^ w >> 8;
+			wtable[(k << 8) + i] = w ^ (k? wtable[0]: 0);
+		}
+}
+
+void ethernet_crc32(const void* data, size_t n_bytes, uint32_t* crc) {
+	static uint32_t table[0x100], wtable[0x100*sizeof(accum_t)];
+	size_t n_accum = n_bytes/sizeof(accum_t);
+	if(!*table)
+		init_tables(table, wtable);
+	for(size_t i = 0; i < n_accum; ++i) {
+		accum_t a = *crc ^ ((accum_t*)data)[i];
+		for(size_t j = *crc = 0; j < sizeof(accum_t); ++j)
+			*crc ^= wtable[(j << 8) + (uint8_t)(a >> 8*j)];
+	}
+	for(size_t i = n_accum*sizeof(accum_t); i < n_bytes; ++i)
+		*crc = table[(uint8_t)*crc ^ ((uint8_t*)data)[i]] ^ *crc >> 8;
+}