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OpenModem/protocol/KISS.c

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#include <stdlib.h>
#include <string.h>
#include "device.h"
#include "hardware/Serial.h"
#include "hardware/LED.h"
#include "hardware/Crypto.h"
#include "util/FIFO16.h"
#include "util/time.h"
#include "KISS.h"
uint8_t packet_queue[CONFIG_QUEUE_SIZE];
uint8_t tx_buffer[AX25_MAX_FRAME_LEN];
volatile uint8_t queue_height = 0;
volatile size_t queued_bytes = 0;
volatile size_t queue_cursor = 0;
volatile size_t current_packet_start = 0;
FIFOBuffer16 packet_starts;
size_t packet_starts_buf[CONFIG_QUEUE_MAX_LENGTH+1];
FIFOBuffer16 packet_lengths;
size_t packet_lengths_buf[CONFIG_QUEUE_MAX_LENGTH+1];
AX25Ctx *ax25ctx;
Afsk *channel;
Serial *serial;
volatile ticks_t last_serial_read = 0;
size_t frame_len;
bool IN_FRAME;
bool ESCAPE;
uint8_t command = CMD_UNKNOWN;
unsigned long custom_preamble = CONFIG_AFSK_PREAMBLE_LEN;
unsigned long custom_tail = CONFIG_AFSK_TRAILER_LEN;
unsigned long slotTime = 200;
uint8_t p = CONFIG_CSMA_P;
void kiss_init(AX25Ctx *ax25, Afsk *afsk, Serial *ser) {
ax25ctx = ax25;
serial = ser;
channel = afsk;
memset(packet_queue, 0, sizeof(packet_queue));
memset(packet_starts_buf, 0, sizeof(packet_starts));
memset(packet_lengths_buf, 0, sizeof(packet_lengths));
fifo16_init(&packet_starts, packet_starts_buf, sizeof(packet_starts_buf));
fifo16_init(&packet_lengths, packet_lengths_buf, sizeof(packet_lengths_buf));
}
void kiss_poll(void) {
while (!fifo_isempty_locked(&uart0FIFO)) {
char sbyte = fifo_pop_locked(&uart0FIFO);
kiss_serialCallback(sbyte);
last_serial_read = timer_clock();
}
}
#if CONFIG_BENCHMARK_MODE
size_t decodes = 0;
#endif
void kiss_messageCallback(AX25Ctx *ctx) {
#if CONFIG_BENCHMARK_MODE
decodes++;
printf("%d\r\n", decodes);
#else
bool integrity_ok = false;
if (crypto_enabled()) {
size_t rxpos = 0;
// Get padding size
uint8_t padding = ctx->buf[rxpos++];
size_t data_length = ctx->frame_len - 2 - 1 - CRYPTO_HMAC_SIZE - CRYPTO_KEY_SIZE;
size_t hmac_offset = ctx->frame_len - 2 - CRYPTO_HMAC_SIZE;
// Get HMAC
uint8_t hmac[CRYPTO_HMAC_SIZE];
memset(hmac, 0x00, CRYPTO_HMAC_SIZE);
for (uint8_t i = 0; i < CRYPTO_HMAC_SIZE; i++) {
size_t pos = hmac_offset + i;
hmac[i] = ctx->buf[pos];
}
// Calculate HMAC
crypto_generate_hmac(ctx->buf, ctx->frame_len-2-CRYPTO_HMAC_SIZE);
bool HMAC_ok = true;
for (uint8_t i = 0; i < CRYPTO_HMAC_SIZE; i++) {
if (hmac[i] != crypto_work_block[i]) {
HMAC_ok = false;
}
}
if (HMAC_ok) {
// Get IV
for (uint8_t i = 0; i < CRYPTO_KEY_SIZE; i++) {
crypto_work_block[i] = ctx->buf[rxpos++];
}
crypto_set_iv_from_workblock();
crypto_prepare();
uint8_t blocks = data_length / CRYPTO_KEY_SIZE;
size_t decrypted_pos = 0;
for (uint8_t block = 0; block < blocks; block++) {
for (uint8_t i = 0; i < CRYPTO_KEY_SIZE; i++) {
crypto_work_block[i] = ctx->buf[rxpos++];
}
crypto_decrypt_block(crypto_work_block);
for (uint8_t i = 0; i < CRYPTO_KEY_SIZE; i++) {
ctx->buf[decrypted_pos++] = crypto_work_block[i];
}
}
ctx->frame_len = data_length - padding;
integrity_ok = true;
}
} else {
integrity_ok = true;
}
if (integrity_ok) {
fputc(FEND, &serial->uart0);
fputc(0x00, &serial->uart0);
for (unsigned i = 0; i < ctx->frame_len-2; i++) {
uint8_t b = ctx->buf[i];
if (b == FEND) {
fputc(FESC, &serial->uart0);
fputc(TFEND, &serial->uart0);
} else if (b == FESC) {
fputc(FESC, &serial->uart0);
fputc(TFESC, &serial->uart0);
} else {
fputc(b, &serial->uart0);
}
}
fputc(FEND, &serial->uart0);
}
#endif
}
void kiss_csma(void) {
if (queue_height > 0) {
#if BITRATE == 2400
if (!channel->hdlc.dcd) {
ticks_t timeout = last_serial_read + ms_to_ticks(CONFIG_SERIAL_TIMEOUT_MS);
if (timer_clock() > timeout) {
if (p == 255) {
kiss_flushQueue();
} else {
// TODO: Implement real CSMA
kiss_flushQueue();
}
}
}
#else
if (!channel->hdlc.dcd) {
if (p == 255) {
kiss_flushQueue();
} else {
// TODO: Implement real CSMA
kiss_flushQueue();
}
}
#endif
}
}
volatile bool queue_flushing = false;
void kiss_flushQueue(void) {
if (!queue_flushing) {
queue_flushing = true;
size_t processed = 0;
for (size_t n = 0; n < queue_height; n++) {
size_t start = fifo16_pop_locked(&packet_starts);
size_t length = fifo16_pop_locked(&packet_lengths);
if (crypto_enabled()) {
uint8_t padding = CRYPTO_KEY_SIZE - (length % CRYPTO_KEY_SIZE);
if (padding == CRYPTO_KEY_SIZE) padding = 0;
uint8_t blocks = (length + padding) / CRYPTO_KEY_SIZE;
if (crypto_generate_iv()) {
crypto_prepare();
size_t tx_pos = 0;
tx_buffer[tx_pos++] = padding;
uint8_t *iv = crypto_get_iv();
for (uint8_t i = 0; i < CRYPTO_KEY_SIZE; i++) {
tx_buffer[tx_pos++] = iv[i];
}
// Encrypt each block
for (uint8_t i = 0; i < blocks; i++) {
if (i < blocks-1 || padding == 0) {
for (uint8_t j = 0; j < CRYPTO_KEY_SIZE; j++) {
size_t pos = (start+j)%CONFIG_QUEUE_SIZE;
crypto_work_block[j] = packet_queue[pos];
}
start += CRYPTO_KEY_SIZE;
} else {
for (uint8_t j = 0; j < CRYPTO_KEY_SIZE - padding; j++) {
size_t pos = (start+j)%CONFIG_QUEUE_SIZE;
crypto_work_block[j] = packet_queue[pos];
}
for (uint8_t j = 0; j < padding; j++) {
crypto_work_block[j] = 0xFF;
}
}
crypto_encrypt_block(crypto_work_block);
for (uint8_t j = 0; j < CRYPTO_KEY_SIZE; j++) {
tx_buffer[tx_pos++] = crypto_work_block[j];
}
}
// Genereate MAC
crypto_generate_hmac(tx_buffer, tx_pos);
for (uint8_t i = 0; i < CRYPTO_HMAC_SIZE; i++) {
tx_buffer[tx_pos++] = crypto_work_block[i];
}
// Check size and send
if (tx_pos <= AX25_MAX_FRAME_LEN) {
ax25_sendRaw(ax25ctx, tx_buffer, tx_pos);
processed++;
} else {
processed++;
}
} else {
LED_indicate_error_crypto();
}
} else {
for (size_t i = 0; i < length; i++) {
size_t pos = (start+i)%CONFIG_QUEUE_SIZE;
tx_buffer[i] = packet_queue[pos];
}
ax25_sendRaw(ax25ctx, tx_buffer, length);
processed++;
}
}
if (processed < queue_height) {
while (true) {
LED_TX_ON();
LED_RX_ON();
}
}
queue_height = 0;
queued_bytes = 0;
queue_flushing = false;
}
}
void kiss_serialCallback(uint8_t sbyte) {
if (IN_FRAME && sbyte == FEND && command == CMD_DATA) {
IN_FRAME = false;
if (queue_height < CONFIG_QUEUE_MAX_LENGTH && queued_bytes < CONFIG_QUEUE_SIZE) {
queue_height++;
size_t s = current_packet_start;
size_t e = queue_cursor-1; if (e == -1) e = CONFIG_QUEUE_SIZE-1;
size_t l = (s < e) ? e - s + 1 : CONFIG_QUEUE_SIZE - s + e + 1;
fifo16_push_locked(&packet_starts, s);
fifo16_push_locked(&packet_lengths, l);
current_packet_start = queue_cursor;
}
} else if (sbyte == FEND) {
IN_FRAME = true;
command = CMD_UNKNOWN;
frame_len = 0;
} else if (IN_FRAME && frame_len < AX25_MAX_PAYLOAD) {
// Have a look at the command byte first
if (frame_len == 0 && command == CMD_UNKNOWN) {
// OpenModem supports only one HDLC port, so we
// strip off the port nibble of the command byte
sbyte = sbyte & 0x0F;
command = sbyte;
if (command == CMD_DATA) current_packet_start = queue_cursor;
} else if (command == CMD_DATA) {
if (sbyte == FESC) {
ESCAPE = true;
} else {
if (ESCAPE) {
if (sbyte == TFEND) sbyte = FEND;
if (sbyte == TFESC) sbyte = FESC;
ESCAPE = false;
}
if (queue_height < CONFIG_QUEUE_MAX_LENGTH && queued_bytes < CONFIG_QUEUE_SIZE) {
queued_bytes++;
packet_queue[queue_cursor++] = sbyte;
if (queue_cursor == CONFIG_QUEUE_SIZE) queue_cursor = 0;
}
}
} else if (command == CMD_TXDELAY) {
custom_preamble = sbyte * 10UL;
} else if (command == CMD_TXTAIL) {
custom_tail = sbyte * 10;
} else if (command == CMD_SLOTTIME) {
slotTime = sbyte * 10;
} else if (command == CMD_P) {
p = sbyte;
} else if (command == CMD_FLUSHQUEUE) {
kiss_flushQueue();
} else if (command == CMD_LED_INTENSITY) {
if (sbyte == FESC) {
ESCAPE = true;
} else {
if (ESCAPE) {
if (sbyte == TFEND) sbyte = FEND;
if (sbyte == TFESC) sbyte = FESC;
ESCAPE = false;
}
LED_setIntensity(sbyte);
}
}
}
}
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