nrf_rpc: Two-way handshake initialization

Implement two-way handshake nRF RPC initialization:
When an initialization packet with the unknown destination
group ID is received, reply to that with an initialization
packet with the right destination group ID.

This makes it possible to re-establish the link even if
either peer has rebooted, or has booted with a delay.

Also, allow to configure infinite group init timeout.

Signed-off-by: Damian Krolik <[email protected]>

nrf_rpc/Kconfig

@@ -40,13 +40,11 @@ config NRF_RPC_CMD_CTX_POOL_SIZE
 	  threads in both local and remote pool.
 
 config NRF_RPC_GROUP_INIT_WAIT_TIME
-	int "Group initialization timeout"
+	int "Group initialization timeout in milliseconds"
 	default 1000
-	range 10 5000
 	help
-	  The time period to wait for the remote cores to send group init responses with
-	  destination group ids.
-	  The time is given in miliseconds.
+	  The number of milliseconds to wait for the remote cores to send group
+	  init packets with destination group ids. Set to -1 to wait forever.
 
 config NRF_RPC_THREAD_POOL_SIZE
 	int "Number of threads in local thread pool"

nrf_rpc/nrf_rpc.c

@@ -297,7 +297,7 @@ static int group_init_send(const struct nrf_rpc_group *group)
 	hdr.type = NRF_RPC_PACKET_TYPE_INIT;
 	hdr.id = 0;
 	hdr.src_group_id = group->data->src_group_id;
-	hdr.dst_group_id = NRF_RPC_ID_UNKNOWN;
+	hdr.dst_group_id = group->data->dst_group_id;
 
 	len = strlen(group->strid) + NRF_RPC_PROTOCOL_VERSION_FIELD_SIZE;
 
@@ -518,8 +518,7 @@ static bool protocol_version_check(const struct init_packet_data *init_data)
 
 	return false;
 }
-static const struct nrf_rpc_group *remote_group_init(uint8_t src_group_id, const char *strid,
-						     size_t strid_len)
+static const struct nrf_rpc_group *group_from_strid(const char *strid, size_t strid_len)
 {
 	void *iter;
 	const struct nrf_rpc_group *group;
@@ -528,16 +527,10 @@ static const struct nrf_rpc_group *remote_group_init(uint8_t src_group_id, const
 				 const struct nrf_rpc_group)) {
 		if ((strid_len == strlen(group->strid)) &&
 		    (memcmp(strid, group->strid, strid_len) == 0)) {
-			group->data->dst_group_id = src_group_id;
-			NRF_RPC_DBG("Found corresponding local group. Remote id: %d, Local id: %d",
-				    src_group_id, group->data->dst_group_id);
-
 			return group;
 		}
 	}
 
-	NRF_RPC_ERR("Remote group does not match local group");
-
 	return NULL;
 }
 
@@ -578,6 +571,8 @@ static int init_packet_handle(struct header *hdr, const struct nrf_rpc_group **g
 {
 	int err;
 	struct init_packet_data init_data = {0};
+	struct nrf_rpc_group_data *group_data;
+	bool first_init;
 
 	*group = NULL;
 
@@ -597,19 +592,38 @@ static int init_packet_handle(struct header *hdr, const struct nrf_rpc_group **g
 	}
 
 	/* Check for the corresponding local group and initialize it. */
-	*group = remote_group_init(hdr->src_group_id, init_data.strid, init_data.strid_len);
+	*group = group_from_strid(init_data.strid, init_data.strid_len);
 	if (*group == NULL) {
+		NRF_RPC_ERR("Remote group does not match local group");
 		NRF_RPC_ASSERT(false);
 		return -NRF_EFAULT;
 	}
 
-	initialized_group_count++;
-	if (initialized_group_count == group_count) {
+	group_data = (**group).data;
+	first_init = group_data->dst_group_id == NRF_RPC_ID_UNKNOWN;
+	group_data->dst_group_id = hdr->src_group_id;
+
+	NRF_RPC_DBG("Found corresponding local group. Remote id: %d, Local id: %d",
+		    hdr->src_group_id, group_data->src_group_id);
+
+	if (first_init && ++initialized_group_count == group_count) {
 		/* All group are initialized. */
 		nrf_rpc_os_event_set(&groups_init_event);
 	}
 
-	return 0;
+	if (hdr->dst_group_id == NRF_RPC_ID_UNKNOWN) {
+		/*
+		 * If remote processor does not know our group id, send an init packet back,
+		 * since it might have missed our original init packet.
+		 */
+		err = group_init_send(*group);
+		if (err) {
+			NRF_RPC_ERR("Failed to send group init packet for group id: %d strid: %s",
+				    group_data->src_group_id, (**group).strid);
+		}
+	}
+
+	return err;
 }
 
 /* Callback from transport layer that handles incoming. */