diff --git a/include/patty/ax25.h b/include/patty/ax25.h index a1337d6..9cf4d6a 100644 --- a/include/patty/ax25.h +++ b/include/patty/ax25.h @@ -51,12 +51,13 @@ typedef struct _patty_ax25_frame { enum patty_ax25_frame_type type; - void * payload; - size_t len; + uint8_t control; + uint8_t proto; - uint8_t control; - uint8_t proto; - uint16_t fcs; + void * payload; + size_t payloadsz; + + size_t size; } patty_ax25_frame; int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len); diff --git a/src/ax25.c b/src/ax25.c index b783f57..4a6852f 100644 --- a/src/ax25.c +++ b/src/ax25.c @@ -4,62 +4,18 @@ #include -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 -}; - -static inline uint16_t fcs_compute(uint8_t *data, size_t len) { - uint16_t fcs = 0xffff; - - while (len--) { - fcs = (fcs >> 8) ^ fcs_table[(fcs ^ ((uint16_t)*data)) & 0x00ff]; - data++; - } - - return fcs; -} +#include "byteorder.h" static ssize_t frame_decode_address(patty_ax25_address *address, void *data, off_t offset) { int i, space = 0; - uint8_t ssid = (((uint8_t *)data) + offset)[6]; + 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 b = (((uint8_t *)data) + offset)[i]; + uint8_t b = ((uint8_t *)data + offset)[i]; uint8_t c = b >> 1; if (!PATTY_AX25_ADDRESS_CHAR_VALID(c) || PATTY_AX25_ADDRESS_OCTET_LAST(b)) { @@ -148,31 +104,27 @@ 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]; +static ssize_t frame_decode_control(patty_ax25_frame *frame, void *data, off_t offset) { + uint8_t control = ((uint8_t *)data + offset)[0]; size_t decoded = 0; - /* - * First, decode the control byte. - */ + int info = 0; + frame->control = control; decoded++; if (PATTY_AX25_CONTROL_INFO(control)) { - frame->type = PATTY_AX25_FRAME_INFO; - frame->proto = ((uint8_t *)data)[1]; + frame->type = PATTY_AX25_FRAME_INFO; - decoded++; + info = 1; } 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++; + info = 1; } } else { frame->type = PATTY_AX25_FRAME_UNKNOWN; @@ -182,7 +134,20 @@ static ssize_t frame_decode_payload(patty_ax25_frame *frame, void *data, off_t o goto error; } - fprintf(stderr, "Decoded %lu bytes\n", decoded); + /* + * If we've received either an Info or Unnumbered Info frame, then decode + * the Protocol Identifier field, and calculate the location and size of + * the payload as well. + */ + if (info) { + decoded++; + + frame->proto = ((uint8_t *)data + offset)[1]; + frame->payload = (void *)((uint8_t *)data + offset + decoded); + frame->payloadsz = frame->size - offset - decoded; + + decoded += frame->payloadsz; + } return decoded; @@ -190,12 +155,14 @@ error: return -1; } -int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) { +int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t size) { ssize_t decoded; off_t offset = 0; memset(frame, '\0', sizeof(*frame)); + frame->size = size; + if ((decoded = frame_decode_address(&frame->dest, data, offset)) < 0) { goto error_decode; } else { @@ -213,8 +180,8 @@ int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) { } /* - * Now, if the source address is not the final address in the frame, then - * begin decoding repeater addresses. + * If the source address is not the final address in the frame, begin + * decoding repeater addresses. */ if (!frame->src.last) { if ((decoded = frame_decode_hops(frame, data, offset)) < 0) { @@ -224,18 +191,18 @@ int patty_ax25_frame_decode(patty_ax25_frame *frame, void *data, size_t len) { } } - fprintf(stderr, "Decoded %ld/%lu\n", offset, len); - /* - * Time to decode the rest of the payload, including control, PID, and - * Frame Check Sequence. + * Now, decode the Control Field, as well as any Protocol Identifier that + * may follow. */ - if ((decoded = frame_decode_payload(frame, data, offset)) < 0) { + if ((decoded = frame_decode_control(frame, data, offset)) < 0) { goto error_decode; } else { offset += decoded; } + fprintf(stderr, "Decoded %lld/%lu bytes\n", offset, size); + return offset; error_decode: