Layer 2: send Empty Packet acknowledgements if there’s nothing else to transmit

This commit is contained in:
Thomas Kolb 2024-07-22 22:19:23 +02:00
parent 87eeb045b0
commit 10a869d1a2
6 changed files with 72 additions and 6 deletions

View file

@ -47,10 +47,25 @@ result_t layer2_rx_handle_packet(layer2_rx_t *ctx, const uint8_t *buf, size_t bu
return ERR_INTEGRITY; return ERR_INTEGRITY;
} }
LOG(LVL_DEBUG, "Handling packet with rx_seq_nr %u, tx_seq_nr %u.", header.rx_seq_nr, header.tx_seq_nr); LOG(LVL_DEBUG, "Handling %s packet with rx_seq_nr %u, tx_seq_nr %u.",
layer2_msg_type_to_string(header.msg_type), header.rx_seq_nr, header.tx_seq_nr);
ctx->last_acked_seq = header.rx_seq_nr; ctx->last_acked_seq = header.rx_seq_nr;
switch(header.msg_type) {
case L2_MSG_TYPE_EMPTY:
LOG(LVL_DEBUG, "Empty packet: accepted ACK for %u.", ctx->last_acked_seq);
return OK; // do not write anything to the TUN device
case L2_MSG_TYPE_CONN_MGMT:
case L2_MSG_TYPE_CONNECTIONLESS:
LOG(LVL_WARN, "Message type %s is not implemented yet.", layer2_msg_type_to_string(header.msg_type));
return OK;
case L2_MSG_TYPE_DATA:
break;
}
if(ctx->next_expected_seq != header.tx_seq_nr) { if(ctx->next_expected_seq != header.tx_seq_nr) {
LOG(LVL_ERR, "Expected sequence number %u, received %u.", ctx->next_expected_seq, header.tx_seq_nr); LOG(LVL_ERR, "Expected sequence number %u, received %u.", ctx->next_expected_seq, header.tx_seq_nr);
return ERR_SEQUENCE; return ERR_SEQUENCE;

View file

@ -94,6 +94,29 @@ result_t layer2_tx_fill_packet_queue(layer2_tx_t *ctx)
} }
result_t layer2_tx_add_empty_packet(layer2_tx_t *ctx, bool tx_request)
{
if(packet_queue_get_free_space(&ctx->packet_queue) == 0) {
return ERR_NO_MEM;
}
layer2_packet_header_t header;
header.dst_addr.addr[0] = 0xFFFF;
header.dst_addr.length = 1;
header.src_addr.addr[0] = 0x0001;
header.src_addr.length = 1;
header.msg_type = L2_MSG_TYPE_EMPTY;
header.rx_seq_nr = 0; // will be filled in layer2_tx_encode_next_packet()
header.tx_seq_nr = 0; // not used in empty packets
header.tx_request = tx_request;
packet_queue_add(&ctx->packet_queue, &header, NULL, 0);
return OK;
}
size_t layer2_tx_encode_next_packet(layer2_tx_t *ctx, uint8_t ack_seq_nr, uint8_t *buf, size_t buf_len) size_t layer2_tx_encode_next_packet(layer2_tx_t *ctx, uint8_t ack_seq_nr, uint8_t *buf, size_t buf_len)
{ {
const packet_queue_entry_t *entry = packet_queue_get(&ctx->packet_queue, ctx->next_packet_index); const packet_queue_entry_t *entry = packet_queue_get(&ctx->packet_queue, ctx->next_packet_index);
@ -116,7 +139,10 @@ size_t layer2_tx_encode_next_packet(layer2_tx_t *ctx, uint8_t ack_seq_nr, uint8_
size_t packet_size = layer2_encode_packet_header(&header, buf); size_t packet_size = layer2_encode_packet_header(&header, buf);
// add the payload data // add the payload data
memcpy(buf + packet_size, entry->data, entry->data_len); if(entry->data) {
memcpy(buf + packet_size, entry->data, entry->data_len);
}
packet_size += entry->data_len; packet_size += entry->data_len;
// calculate CRC of everything and append it to the packet // calculate CRC of everything and append it to the packet
@ -155,8 +181,15 @@ void layer2_tx_handle_ack(layer2_tx_t *ctx, uint8_t acked_seq)
packet_queue_delete(&ctx->packet_queue, packets_to_remove); packet_queue_delete(&ctx->packet_queue, packets_to_remove);
LOG(LVL_DEBUG, "handling ack for seq_nr %u, removing %zu packets, %zu packets remaining.", acked_seq, packets_to_remove, packet_queue_get_used_space(&ctx->packet_queue)); packets_available = packet_queue_get_used_space(&ctx->packet_queue);
LOG(LVL_DEBUG, "handling ack for seq_nr %u, removing %zu packets, %zu packets remaining.", acked_seq, packets_to_remove, packets_available);
if(packets_available == 0) {
// no packets left in queue, but an acknowledgement must be
// transmitted. Add an empty packet to do that.
layer2_tx_add_empty_packet(ctx, false);
}
} }

View file

@ -32,6 +32,12 @@ void layer2_tx_destroy(layer2_tx_t *ctx);
*/ */
result_t layer2_tx_fill_packet_queue(layer2_tx_t *ctx); result_t layer2_tx_fill_packet_queue(layer2_tx_t *ctx);
/*!\brief Add an empty packet to ensure an acknowledgement is sent.
* \param ctx The transmitter context.
* \param tx_request Value of the TX Request field in the packet.
*/
result_t layer2_tx_add_empty_packet(layer2_tx_t *ctx, bool tx_request);
/*!\brief Encode the next packet for transmission. /*!\brief Encode the next packet for transmission.
* *
* \note * \note

View file

@ -61,7 +61,11 @@ void packet_queue_delete(packet_queue_t *q, size_t count)
packet_queue_entry_t *entry = &q->entries[q->read_idx]; packet_queue_entry_t *entry = &q->entries[q->read_idx];
free(entry->data); if(entry->data) {
free(entry->data);
entry->data = NULL;
}
entry->data_len = 0; entry->data_len = 0;
q->read_idx++; q->read_idx++;

View file

@ -72,20 +72,23 @@ bool layer2_decode_packet_header(const uint8_t *encoded, size_t encoded_len, lay
} }
static const char* msg_type_to_string(layer2_message_type_t type) const char* layer2_msg_type_to_string(layer2_message_type_t type)
{ {
switch(type) { switch(type) {
case L2_MSG_TYPE_CONNECTIONLESS: return "Connectionless"; case L2_MSG_TYPE_CONNECTIONLESS: return "Connectionless";
case L2_MSG_TYPE_DATA: return "Data"; case L2_MSG_TYPE_DATA: return "Data";
case L2_MSG_TYPE_CONN_MGMT: return "Connection Management"; case L2_MSG_TYPE_CONN_MGMT: return "Connection Management";
case L2_MSG_TYPE_EMPTY: return "Empty";
} }
return "!UNHANDLED TYPE!";
} }
void layer2_dump_packet_header(int level, const layer2_packet_header_t *header) void layer2_dump_packet_header(int level, const layer2_packet_header_t *header)
{ {
LOG(level, "Packet header dump:"); LOG(level, "Packet header dump:");
LOG(level, " Packet type: %s", msg_type_to_string(header->msg_type)); LOG(level, " Packet type: %s", layer2_msg_type_to_string(header->msg_type));
LOG(level, " TX Request: %s", header->tx_request ? "true" : "false"); LOG(level, " TX Request: %s", header->tx_request ? "true" : "false");
LOG(level, " RX Seq. Nr: %2u", header->rx_seq_nr); LOG(level, " RX Seq. Nr: %2u", header->rx_seq_nr);
LOG(level, " TX Seq. Nr: %2u", header->tx_seq_nr); LOG(level, " TX Seq. Nr: %2u", header->tx_seq_nr);

View file

@ -12,6 +12,7 @@
typedef enum { typedef enum {
L2_MSG_TYPE_DATA = 0x0, L2_MSG_TYPE_DATA = 0x0,
L2_MSG_TYPE_CONN_MGMT = 0x1, L2_MSG_TYPE_CONN_MGMT = 0x1,
L2_MSG_TYPE_EMPTY = 0x2,
L2_MSG_TYPE_CONNECTIONLESS = 0x4 L2_MSG_TYPE_CONNECTIONLESS = 0x4
} layer2_message_type_t; } layer2_message_type_t;
@ -67,6 +68,10 @@ bool layer2_decode_packet_header(const uint8_t *encoded, size_t encoded_len, lay
*/ */
void layer2_dump_packet_header(int level, const layer2_packet_header_t *header); void layer2_dump_packet_header(int level, const layer2_packet_header_t *header);
/*!\brief Get a string representation of the given message type.
*/
const char* layer2_msg_type_to_string(layer2_message_type_t type);
/* Data Packet Structs */ /* Data Packet Structs */
typedef enum { typedef enum {