[PATCH net-next 10/15] batman-adv: tvlv: extract tvlv header iterator

[Simon Wunderlich <sw@simonwunderlich.de>]

From: Sven Eckelmann <sven@narfation.org>

batadv_tvlv_containers_contain() and batadv_tvlv_containers_process() are
using the same code to iterate through the TVLV containers. To simplify the
code, extract the shared portions of both functions.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
---
 net/batman-adv/tvlv.c | 86 +++++++++++++++++++++++++------------------
 1 file changed, 51 insertions(+), 35 deletions(-)

diff --git a/net/batman-adv/tvlv.c b/net/batman-adv/tvlv.c
index 1c9fb21985f6a..49bf2ed9ecdc3 100644
--- a/net/batman-adv/tvlv.c
+++ b/net/batman-adv/tvlv.c
@@ -442,6 +442,54 @@ static int batadv_tvlv_call_handler(struct batadv_priv *bat_priv,
 	return NET_RX_SUCCESS;
 }
 
+/**
+ * batadv_tvlv_hdr_next() - move a tvlv buffer cursor to the next container
+ * @tvlv_value: cursor into the tvlv buffer, advanced past the returned
+ *  container's content on success
+ * @tvlv_value_len: remaining length of the tvlv buffer, reduced by the returned
+ *  container's size on success
+ *
+ * Parses a single container header at the current cursor position and, if a
+ * complete container is available, advances the cursor and remaining length
+ * past it. The returned header stays valid; its content is located at
+ * (returned header + 1) and is ntohs(hdr->len) bytes long.
+ *
+ * Return: pointer to the next tvlv container header, or NULL if no further
+ * complete container is present in the buffer.
+ */
+static struct batadv_tvlv_hdr *batadv_tvlv_hdr_next(void **tvlv_value, u16 *tvlv_value_len)
+{
+	struct batadv_tvlv_hdr *tvlv_hdr;
+	u16 tvlv_value_cont_len;
+	void *tvlv_value_cont;
+	u16 tvlv_len;
+
+	tvlv_value_cont = *tvlv_value;
+	tvlv_len = *tvlv_value_len;
+
+	if (tvlv_len < sizeof(*tvlv_hdr))
+		return NULL;
+
+	tvlv_hdr = tvlv_value_cont;
+	tvlv_value_cont_len = ntohs(tvlv_hdr->len);
+	tvlv_value_cont = tvlv_hdr + 1;
+	tvlv_len -= sizeof(*tvlv_hdr);
+
+	if (tvlv_value_cont_len > tvlv_len)
+		return NULL;
+
+	/* the next tvlv header is accessed assuming (at least) 2-byte
+	 * alignment, so it must start at an even offset.
+	 */
+	if (tvlv_value_cont_len & 1)
+		return NULL;
+
+	*tvlv_value = (u8 *)tvlv_value_cont + tvlv_value_cont_len;
+	*tvlv_value_len = tvlv_len - tvlv_value_cont_len;
+
+	return tvlv_hdr;
+}
+
 /**
  * batadv_tvlv_containers_contain() - check if a tvlv buffer holds a container
  * @tvlv_value: tvlv content
@@ -457,28 +505,10 @@ static bool batadv_tvlv_containers_contain(void *tvlv_value,
 					   u8 version)
 {
 	struct batadv_tvlv_hdr *tvlv_hdr;
-	u16 tvlv_value_cont_len;
-
-	while (tvlv_value_len >= sizeof(*tvlv_hdr)) {
-		tvlv_hdr = tvlv_value;
-		tvlv_value_cont_len = ntohs(tvlv_hdr->len);
-		tvlv_value = tvlv_hdr + 1;
-		tvlv_value_len -= sizeof(*tvlv_hdr);
-
-		if (tvlv_value_cont_len > tvlv_value_len)
-			break;
-
-		/* the next tvlv header is accessed assuming (at least) 2-byte
-		 * alignment, so it must start at an even offset.
-		 */
-		if (tvlv_value_cont_len & 1)
-			break;
 
+	while ((tvlv_hdr = batadv_tvlv_hdr_next(&tvlv_value, &tvlv_value_len))) {
 		if (tvlv_hdr->type == type && tvlv_hdr->version == version)
 			return true;
-
-		tvlv_value = (u8 *)tvlv_value + tvlv_value_cont_len;
-		tvlv_value_len -= tvlv_value_cont_len;
 	}
 
 	return false;
@@ -511,20 +541,8 @@ int batadv_tvlv_containers_process(struct batadv_priv *bat_priv,
 	u8 cifnotfound = BATADV_TVLV_HANDLER_OGM_CIFNOTFND;
 	int ret = NET_RX_SUCCESS;
 
-	while (tvlv_value_len >= sizeof(*tvlv_hdr)) {
-		tvlv_hdr = tvlv_value;
+	while ((tvlv_hdr = batadv_tvlv_hdr_next(&tvlv_value, &tvlv_value_len))) {
 		tvlv_value_cont_len = ntohs(tvlv_hdr->len);
-		tvlv_value = tvlv_hdr + 1;
-		tvlv_value_len -= sizeof(*tvlv_hdr);
-
-		if (tvlv_value_cont_len > tvlv_value_len)
-			break;
-
-		/* the next tvlv header is accessed assuming (at least) 2-byte
-		 * alignment, so it must start at an even offset.
-		 */
-		if (tvlv_value_cont_len & 1)
-			break;
 
 		tvlv_handler = batadv_tvlv_handler_get(bat_priv,
 						       tvlv_hdr->type,
@@ -532,11 +550,9 @@ int batadv_tvlv_containers_process(struct batadv_priv *bat_priv,
 
 		ret |= batadv_tvlv_call_handler(bat_priv, tvlv_handler,
 						packet_type, orig_node, skb,
-						tvlv_value,
+						tvlv_hdr + 1,
 						tvlv_value_cont_len);
 		batadv_tvlv_handler_put(tvlv_handler);
-		tvlv_value = (u8 *)tvlv_value + tvlv_value_cont_len;
-		tvlv_value_len -= tvlv_value_cont_len;
 	}
 
 	if (packet_type != BATADV_IV_OGM &&
-- 
2.47.3