patty/src/decode.c

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>

#include <patty/kiss.h>
#include <patty/ax25.h>

static void usage(int argc, char **argv, const char *message, ...) {
    if (message) {
        va_list args;

        va_start(args, message);
        vfprintf(stderr, message, args);
         fprintf(stderr, "\n");
        va_end(args);
    }

    fprintf(stderr, "usage: %s kiss.cap\n", argv[0]);

    exit(1);
}

static int callsign_fprint(FILE *stream, const patty_ax25_address *address) {
    fprintf(stream, "%s", address->callsign);

    if (address->ssid) {
        fprintf(stream, "/%d", address->ssid);
    }

    return 0;
}

#define printable(c) \
    (c >= 0x20 && c < 0x7f)

static int hexdump_fprint(FILE *stream, void *data, size_t len) {
    size_t i;

    for (i=0; i<len; i+=16) {
        size_t x;

        if (fprintf(stream, "%08lx:", i) < 0) {
            goto error_io;
        }

        for (x=0; x<16; x++) {
            if (!(x & 1)) {
                if (fprintf(stream, " ") < 0) {
                    goto error_io;
                }
            }

            if (i+x < len) {
                if (fprintf(stream, "%02x", ((uint8_t *)data)[i+x]) < 0) {
                    goto error_io;
                }
            } else {
                if (fprintf(stream, "  ") < 0) {
                    goto error_io;
                }
            }
        }

        if (fprintf(stream, "  ") < 0) {
            goto error_io;
        }

        for (x=0; x<16 && i+x<len; x++) {
            uint8_t c = ((uint8_t *)data)[i+x];

            if (fputc(printable(c)? c: '.', stream) < 0) {
                goto error_io;
            }
        }

        if (fprintf(stream, "\n") < 0) {
            goto error_io;
        }
    }

    return 0;

error_io:
    return -1;
}

static int address_fprint(FILE *stream, const patty_ax25_frame *frame) {
    int i;

    callsign_fprint(stream, &frame->src);

    fprintf(stream, " > ");

    for (i=0; i<frame->hops; i++) {
        callsign_fprint(stream, &frame->repeaters[i]);
        fprintf(stream, " > ");
    }

    callsign_fprint(stream, &frame->dest);

    return 0;
}

static int frame_fprint(FILE *stream,
                        const patty_ax25_frame *frame,
                        void *data,
                        size_t len) {
    if (address_fprint(stream, frame) < 0) {
        goto error_io;
    }

    if (frame->type == PATTY_AX25_FRAME_INFO) {
        if (fprintf(stream, " type I poll %d ns %d nr %d payload %zu",
                PATTY_AX25_CONTROL_POLL(frame->control),
                PATTY_AX25_CONTROL_SEQ_SEND(frame->control),
                PATTY_AX25_CONTROL_SEQ_RECV(frame->control),
                frame->payloadsz) < 0) {
            goto error_io;
        }
    } else if (frame->type == PATTY_AX25_FRAME_UNNUMBERED) {
        if (fprintf(stream, " type U payload %zu",
                frame->payloadsz) < 0) {
            goto error_io;
        }
    }

    if (fprintf(stream, " total %zu bytes\n", len) < 0) {
        goto error_io;
    }

    if (hexdump_fprint(stream, data, len) < 0) {
        goto error_io;
    }

    return 0;

error_io:
    return -1;
}

int main(int argc, char **argv) {
    patty_kiss_tnc *tnc;
    void *data;
    int port;

    if (argc != 2) {
        usage(argc, argv, "No TNC device provided");
    }

    if ((tnc = patty_kiss_tnc_open(argv[1], PATTY_KISS_BUFSZ)) == NULL) {
        perror("Unable to open TNC");

        goto error_kiss_tnc_open;
    }

    while (1) {
        ssize_t len;
        patty_ax25_frame frame;

        if ((len = patty_kiss_tnc_recv(tnc, &data, &port)) < 0) {
            perror("Unable to read frame");

            goto error_ax25_frame_read;
        } else if (len == 0) {
            break;
        }

        if (patty_ax25_frame_decode(&frame, data, len) < 0) {
            perror("Unable to decode frame");

            goto error_ax25_frame_decode;
        }

        if (frame_fprint(stdout, &frame, data, len) < 0) {
            perror("Unable to print frame");

            goto error_frame_fprint;
        }
    }

    patty_kiss_tnc_close(tnc);

    return 0;

error_frame_fprint:
error_ax25_frame_decode:
error_ax25_frame_read:
    patty_kiss_tnc_close(tnc);

error_kiss_tnc_open:
    return 127;
}