fronius_error_t fronius_pkt_validate(const struct fronius_pkt * pkt)
{
uint8_t *p = (uint8_t *) & pkt->length;
uint8_t checksum = 0;
fronius_error_t err;
int i;
err = fronius_pkt_validate_header(pkt);
if (err)
return err;
/* validate checksum */
i = FRONIUS_HEADERLEN + pkt->length;
while (i--)
checksum += *p++;
if (pkt->checksum != checksum)
return FRONIUS_ERR_CHECKSUM;
/* packet is valid */
return FRONIUS_ERR_NOERROR;
}
int fronius_pkt_recv(struct fronius_dev *dev,
const struct fronius_pkt *pkt)
{
uint8_t buf[FRONIUS_MAX_PKTLEN];
uint8_t crc;
size_t pktlen = FRONIUS_MAX_PKTLEN;
size_t bytes_read = 0;
fd_set rfds;
struct timeval tv;
int rv;
memset(&buf, 0, sizeof(buf));
do {
FD_ZERO(&rfds);
FD_SET(dev->fd, &rfds);
tv.tv_sec = FRONIUS_RECV_TIMEOUT;
tv.tv_usec = 0;
rv = select(dev->fd + 1, &rfds, NULL, NULL, &tv);
} while (rv == -1 && errno == EINTR);
if (rv == -1)
return rv;
/* timed out */
if (rv == 0) {
errno = ETIMEDOUT;
return -1;
}
do {
ssize_t c = read(dev->fd, &buf[bytes_read], pktlen - bytes_read);
if (c <= -1) {
if (errno == EINTR)
continue;
return c;
}
/* got some bytes */
bytes_read += c;
dev->bytes_received += c;
/* does the buffer looks like a packet? */
if (bytes_read >= FRONIUS_MIN_PKTLEN) {
switch (fronius_pkt_validate_header((struct fronius_pkt *) buf)) {
case FRONIUS_ERR_NOERROR:
/* trim read to real packet length after
fronius_pkt_validate_header ensured maximum packet length */
pktlen = buf[FRONIUS_OF_LENGTH] + FRONIUS_MIN_PKTLEN;
break;
default:
/* read data looks strange */
#if 0
fprintf(stderr, "strange data\n");
dump_buf(buf, bytes_read);
#endif
errno = EIO;
return -1;
}
}
} while (bytes_read < pktlen);
/* move crc to end of buffer (use buffer to not override it accidently) */
crc = buf[pktlen - 1];
buf[pktlen - 1] = 0;
buf[FRONIUS_MAX_PKTLEN - 1] = crc;
/* copy buffer to packet */
memcpy((void *) pkt, buf, sizeof(*pkt));
/* update packet counter */
dev->pkts_received++;
gettimeofday(&dev->last_received, NULL);
/* dump packet */
if (dev->debug)
fronius_pkt_dump(NULL, "fronius_pkt_recv", pkt, dev->rawdump);
/* deep packet validation */
switch (fronius_pkt_validate(pkt)) {
case FRONIUS_ERR_NOERROR:
break;
case FRONIUS_ERR_CHECKSUM:
dev->checksum_errors++;
/* fallthrough */
default:
errno = EIO;
return -1;
}
return 0;
}
