net: coap: Add function for removing block transfer option

In some cases the options of a CoAP message are reused for
block transfer. Then the block header needs to be updated.
The current approach is to remove the old block option and
add an updated one.

Signed-off-by: Lukas Woodtli <[email protected]>

Author: LukasWoodtli

include/zephyr/net/coap.h

@@ -606,6 +606,18 @@ int coap_block_transfer_init(struct coap_block_context *ctx,
  */
 int coap_append_descriptive_block_option(struct coap_packet *cpkt, struct coap_block_context *ctx);
 
+/**
+ * @brief Remove BLOCK1 or BLOCK2 option from the packet.
+ *
+ * If the CoAP packet is a request then BLOCK1 is removed
+ * otherwise BLOCK2 is removed.
+ *
+ * @param cpkt Packet to be updated.
+ *
+ * @return 0 in case of success or negative in case of error.
+ */
+int coap_remove_descriptive_block_option(struct coap_packet *cpkt);
+
 /**
  * @brief Append BLOCK1 option to the packet.
  *

subsys/net/lib/coap/coap.c

@@ -1096,6 +1096,15 @@ int coap_append_descriptive_block_option(struct coap_packet *cpkt, struct coap_b
 	}
 }
 
+int coap_remove_descriptive_block_option(struct coap_packet *cpkt)
+{
+	if (is_request(cpkt)) {
+		return coap_packet_remove_option(cpkt, COAP_OPTION_BLOCK1);
+	} else {
+		return coap_packet_remove_option(cpkt, COAP_OPTION_BLOCK2);
+	}
+}
+
 int coap_append_block1_option(struct coap_packet *cpkt,
 			      struct coap_block_context *ctx)
 {