diff --git a/include/patty/ax25.h b/include/patty/ax25.h index 929f721..a1337d6 100644 --- a/include/patty/ax25.h +++ b/include/patty/ax25.h @@ -9,6 +9,7 @@ #define PATTY_AX25_MAX_HOPS 8 enum patty_ax25_proto { + PATTY_AX25_PROTO_UNKNOWN = 0x00, PATTY_AX25_PROTO_ISO_8208 = 0x01, PATTY_AX25_PROTO_TCP_VJ_COMPR = 0x06, PATTY_AX25_PROTO_TCP_VJ = 0x07, @@ -26,14 +27,37 @@ enum patty_ax25_proto { }; enum patty_ax25_frame_type { + PATTY_AX25_FRAME_UNKNOWN, PATTY_AX25_FRAME_INFO, PATTY_AX25_FRAME_SUPER, PATTY_AX25_FRAME_UNNUMBERED }; -typedef struct _patty_ax25_address patty_ax25_address; +typedef struct _patty_ax25_address { + char callsign[7]; -typedef struct _patty_ax25_frame patty_ax25_frame; + int ssid; + int last; + int repeated; +} patty_ax25_address; + +typedef struct _patty_ax25_frame { + patty_ax25_address dest; + patty_ax25_address src; + patty_ax25_address repeaters[8]; + + int hops; + int repeated; + + enum patty_ax25_frame_type type; + + void * payload; + size_t len; + + uint8_t control; + uint8_t proto; + uint16_t fcs; +} patty_ax25_frame; int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len); diff --git a/include/patty/ax25/macros.h b/include/patty/ax25/macros.h index 9cf75dd..0336302 100644 --- a/include/patty/ax25/macros.h +++ b/include/patty/ax25/macros.h @@ -1,8 +1,8 @@ #ifndef _PATTY_AX25_MACROS_H #define _PATTY_AX25_MACROS_H -#define PATTY_AX25_ADDRESS_OCTET_VALID(c) \ - ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || (c == ' ')) +#define PATTY_AX25_ADDRESS_CHAR_VALID(c) \ + ((c >= 0x20 && c <= 0x5a)) #define PATTY_AX25_ADDRESS_OCTET_LAST(c) \ ((c & 0x01) == 0x01) @@ -55,7 +55,7 @@ #define PATTY_AX25_CONTROL_UNNUMBERED_FRMR(c) \ (((c & 0xe0) == 0x40) && ((c & 0x0f) == 0x07)) -#define PATTY_AX25_CONTROL_UNNUMBERED_UI(c) \ +#define PATTY_AX25_CONTROL_UNNUMBERED_INFO(c) \ (((c & 0xe0) == 0x00) && ((c & 0x0f) == 0x02)) #define PATTY_AX25_CONTROL_SEQ_SEND(c) \ diff --git a/src/ax25.c b/src/ax25.c index fc2791e..b783f57 100644 --- a/src/ax25.c +++ b/src/ax25.c @@ -1,45 +1,68 @@ +#include #include #include #include -struct _patty_ax25_address { - char callsign[7]; - - int ssid; - int last; - int repeated; +uint16_t fcs_table[256] = { + 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, + 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, + 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, + 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, + 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, + 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, + 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, + 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, + 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, + 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, + 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, + 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, + 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, + 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, + 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, + 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, + 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, + 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, + 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, + 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, + 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, + 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, + 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, + 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, + 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, + 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, + 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, + 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, + 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, + 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, + 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, + 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 }; -struct _patty_ax25_frame { - struct _patty_ax25_address dest; - struct _patty_ax25_address src; - struct _patty_ax25_address repeaters[8]; - - int hops; - int repeated; +static inline uint16_t fcs_compute(uint8_t *data, size_t len) { + uint16_t fcs = 0xffff; - enum patty_ax25_frame_type type; - enum patty_ax25_proto proto; + while (len--) { + fcs = (fcs >> 8) ^ fcs_table[(fcs ^ ((uint16_t)*data)) & 0x00ff]; + data++; + } - uint8_t control; - uint8_t pid; - void * info; - uint16_t fcs; -}; + return fcs; +} static ssize_t frame_decode_address(patty_ax25_address *address, void *data, off_t offset) { int i, space = 0; - uint8_t *info = (uint8_t *)data; + uint8_t ssid = (((uint8_t *)data) + offset)[6]; /* * First, unpack each callsign octet, ensuring all are within the 7 bit * ASCII space and do not have the extended bit set to 1. */ for (i=0; i<6; i++) { - uint8_t c = (((uint8_t *)data) + offset)[i]; + uint8_t b = (((uint8_t *)data) + offset)[i]; + uint8_t c = b >> 1; - if (!PATTY_AX25_ADDRESS_OCTET_VALID(c) || !PATTY_AX25_ADDRESS_OCTET_LAST(c)) { + if (!PATTY_AX25_ADDRESS_CHAR_VALID(c) || PATTY_AX25_ADDRESS_OCTET_LAST(b)) { errno = EINVAL; goto error; @@ -66,16 +89,16 @@ static ssize_t frame_decode_address(patty_ax25_address *address, void *data, off goto error; } - address->callsign[i] = c >> 1; + address->callsign[i] = c; } } /* * Now, unpack the data from the SSID field. */ - address->repeated = PATTY_AX25_ADDRESS_SSID_REPEATED(info[7]); - address->ssid = PATTY_AX25_ADDRESS_SSID_NUMBER(info[7]); - address->last = PATTY_AX25_ADDRESS_OCTET_LAST(info[7]); + address->repeated = PATTY_AX25_ADDRESS_SSID_REPEATED(ssid); + address->ssid = PATTY_AX25_ADDRESS_SSID_NUMBER(ssid); + address->last = PATTY_AX25_ADDRESS_OCTET_LAST(ssid); return 7; @@ -83,14 +106,98 @@ error: return -1; } -int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) { +static ssize_t frame_decode_hops(patty_ax25_frame *frame, void *data, off_t start) { + ssize_t decoded; + off_t offset = start; + + int i; + + /* + * Try to decode the AX.25-specified maximum number of hops in the current + * frame. + */ + for (i=0; irepeaters[i], data, offset)) < 0) { + goto error; + } else { + offset += decoded; + } + + frame->hops++; + + if (frame->repeaters[i].last) { + frame->repeated = frame->repeaters[i].repeated; + + break; + } + } + + /* + * If the last hop does not have the address extension bit set, then + * that's a big problem. + */ + if (frame->hops && !frame->repeaters[frame->hops-1].last) { + errno = EINVAL; + + goto error; + } + + return offset - start; + +error: + return -1; +} + +static ssize_t frame_decode_payload(patty_ax25_frame *frame, void *data, off_t offset) { + uint8_t control = ((uint8_t *)data)[0]; + size_t decoded = 0; + + /* + * First, decode the control byte. + */ + frame->control = control; + + decoded++; + + if (PATTY_AX25_CONTROL_INFO(control)) { + frame->type = PATTY_AX25_FRAME_INFO; + frame->proto = ((uint8_t *)data)[1]; + + decoded++; + } else if (PATTY_AX25_CONTROL_SUPER(control)) { + frame->type = PATTY_AX25_FRAME_SUPER; + } else if (PATTY_AX25_CONTROL_UNNUMBERED(control)) { + frame->type = PATTY_AX25_FRAME_UNNUMBERED; + + if (PATTY_AX25_CONTROL_UNNUMBERED_INFO(control)) { + frame->proto = ((uint8_t *)data)[1]; + + decoded++; + } + } else { + frame->type = PATTY_AX25_FRAME_UNKNOWN; + + errno = EINVAL; + + goto error; + } + + fprintf(stderr, "Decoded %lu bytes\n", decoded); + + return decoded; + +error: + return -1; +} + +int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) { ssize_t decoded; off_t offset = 0; memset(frame, '\0', sizeof(*frame)); if ((decoded = frame_decode_address(&frame->dest, data, offset)) < 0) { - goto error_decode_dest; + goto error_decode; } else { offset += decoded; } @@ -99,9 +206,8 @@ int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) { * It would be considered erroneous if the destination address did have the * extension bit set to 1. */ - if ((decoded = frame_decode_address(&frame->src, data, offset)) < 0) { - goto error_decode_src; + goto error_decode; } else { offset += decoded; } @@ -111,37 +217,27 @@ int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) { * begin decoding repeater addresses. */ if (!frame->src.last) { - int i; - - for (i=0; irepeaters[i], data, offset)) < 0) { - goto error_decode_repeater; - } - - frame->hops++; - - if (frame->repeaters[i].last) { - frame->repeated = frame->repeaters[i].repeated; - - break; - } - } - - /* - * If the last hop does not have the address extension bit set, then - * that's a big problem. - */ - if (frame->hops && !frame->repeaters[i-1].last) { - errno = EINVAL; - - goto error_decode_repeater; + if ((decoded = frame_decode_hops(frame, data, offset)) < 0) { + goto error_decode; + } else { + offset += decoded; } } - return 0; + fprintf(stderr, "Decoded %ld/%lu\n", offset, len); -error_decode_repeater: -error_decode_src: -error_decode_dest: + /* + * Time to decode the rest of the payload, including control, PID, and + * Frame Check Sequence. + */ + if ((decoded = frame_decode_payload(frame, data, offset)) < 0) { + goto error_decode; + } else { + offset += decoded; + } + + return offset; + +error_decode: return -1; } diff --git a/src/test.c b/src/test.c index 6df0558..4b2fb5e 100644 --- a/src/test.c +++ b/src/test.c @@ -5,6 +5,7 @@ #include #include +#include static void usage(int argc, char **argv, const char *message, ...) { if (message) { @@ -21,10 +22,35 @@ static void usage(int argc, char **argv, const char *message, ...) { 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; +} + +static int address_fprint(FILE *stream, const patty_ax25_frame *frame) { + int i; + + callsign_fprint(stream, &frame->src); + fprintf(stream, " > "); + callsign_fprint(stream, &frame->dest); + + for (i=0; ihops; i++) { + fprintf(stream, " < "); + callsign_fprint(stream, &frame->repeaters[i]); + } + + return 0; +} + int main(int argc, char **argv) { patty_kiss_tnc *tnc; ssize_t len; - void *frame; + void *data; int port; if (argc != 2) { @@ -37,10 +63,17 @@ int main(int argc, char **argv) { exit(127); } - while ((len = patty_kiss_tnc_recv(tnc, &frame, &port)) > 0) { - write(fileno(stdout), frame, len); + while ((len = patty_kiss_tnc_recv(tnc, &data, &port)) > 0) { + patty_ax25_frame frame; - fprintf(stderr, "Got %ld byte frame\n", len); + if (patty_ax25_frame_decode(&frame, data, len) < 0) { + perror("Unable to decode frame"); + + exit(127); + } + + address_fprint(stderr, &frame); + fprintf(stderr, " %ld bytes\n", len); } patty_kiss_tnc_close(tnc);