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Fix BACnet APDU parsing with segmentable messages #18

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Fix BACnet APDU parsing with segmentable messages #18

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13 changes: 10 additions & 3 deletions src/protocols/bacnet.c
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Original file line number Diff line number Diff line change
Expand Up @@ -108,27 +108,34 @@ static void bacnet_dump(FILE* fp, const struct header_chunk* header, const char*
size_t apdu_len = payload_len - offset;

uint8_t apdu_header = apdu[0];
uint8_t offsetFlags = 0;
uint8_t pdu_type = apdu_header >> 4;
uint8_t pdu_flags = apdu_header & 0x0F;

fprintf(fp,"%sPDU Type: %u\n", prefix, pdu_type);
fprintf(fp,"%sFlags: %u\n", prefix, pdu_flags);

if (pdu_flags & 0x08) {
offsetFlags = 2; // Segmentable
} else {
offsetFlags = 0;
}

if (pdu_type <= 0x04) {
if (apdu_len >= 2) {
if (pdu_type == 0x01) {
fprintf(fp,"%sService Type: %u\n", prefix, apdu[1]);
fprintf(fp,"%sService Type: %u\n", prefix, apdu[1 + offsetFlags]);
}
else if (pdu_type == 0x04) {
fprintf(fp,"%sInvoke ID: %u (Segment ACK — no service type)\n", prefix, apdu[1]);
}
else if (pdu_type == 0x00 && apdu_len >= 4) {
uint8_t service_type = apdu[3];
uint8_t service_type = apdu[3 + offsetFlags];
fprintf(fp,"%sInvoke ID: %u\n", prefix, apdu[2]);
fprintf(fp,"%sService Type: %u\n", prefix, service_type);
}
else if (apdu_len >= 3) {
uint8_t service_type = apdu[2];
uint8_t service_type = apdu[2 + offsetFlags];
fprintf(fp,"%sInvoke ID: %u\n", prefix, apdu[1]);
fprintf(fp,"%sService Type: %u\n", prefix, service_type);
}
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