batman-adv: Add function to calculate crc32c for the skb payload

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/net/batman-adv/main.c b/net/batman-adv/main.c
index dc33a0c..f65a222 100644
--- a/net/batman-adv/main.c
+++ b/net/batman-adv/main.c
@@ -17,6 +17,8 @@
  * 02110-1301, USA
  */
 
+#include <linux/crc32c.h>
+#include <linux/highmem.h>
 #include "main.h"
 #include "sysfs.h"
 #include "debugfs.h"
@@ -420,6 +422,38 @@ int batadv_algo_seq_print_text(struct seq_file *seq, void *offset)
 	return 0;
 }
 
+/**
+ * batadv_skb_crc32 - calculate CRC32 of the whole packet and skip bytes in
+ *  the header
+ * @skb: skb pointing to fragmented socket buffers
+ * @payload_ptr: Pointer to position inside the head buffer of the skb
+ *  marking the start of the data to be CRC'ed
+ *
+ * payload_ptr must always point to an address in the skb head buffer and not to
+ * a fragment.
+ */
+__be32 batadv_skb_crc32(struct sk_buff *skb, u8 *payload_ptr)
+{
+	u32 crc = 0;
+	unsigned int from;
+	unsigned int to = skb->len;
+	struct skb_seq_state st;
+	const u8 *data;
+	unsigned int len;
+	unsigned int consumed = 0;
+
+	from = (unsigned int)(payload_ptr - skb->data);
+
+	skb_prepare_seq_read(skb, from, to, &st);
+	while ((len = skb_seq_read(consumed, &data, &st)) != 0) {
+		crc = crc32c(crc, data, len);
+		consumed += len;
+	}
+	skb_abort_seq_read(&st);
+
+	return htonl(crc);
+}
+
 static int batadv_param_set_ra(const char *val, const struct kernel_param *kp)
 {
 	struct batadv_algo_ops *bat_algo_ops;