szpajder / libacars Goto Github PK

First thanks for this lib and your work to include it in acarsdec

I have a question:
I see in acars this kind of message:
#M1B/BA SOUCAYA.CC1.I-NDMJ60412240491075DA
That is perfectly decoded by libacars

But I see too messages that really look like FANS-1/A messagebut that are not decoded:
'#M1B/B0 SOUCAYA.AFN/FMHNOS492,.I-NDMJ,,182449/FRP0A481`

It could be normal, I don't really know ARINC 622

Not an issue, just to let you know that it says in the README that it should build on both Linux i686 and x86_64 - I just built it on a Raspberry Pi 3 with both zlib and libxml2-dev, and it works perfectly :-)

the docs say

The following commands enable these capabilities:
set arinc on
which applies the polynomial: x^16+x^15+x^l3+x^5+x^3+x^1+1

(which corresponds to 0xa02b without leading 1)

set International Telephone and Telegraph Consultative Committee (ccitt) on
which applies the polynomial: x^16+x^12+x^5+1

But in la_crc16_arinc in fact is

name	id	size	polynomial	init	xor_out	reflect_in	reflect_out	check_value
IBM-3740	crc16_ibm3740	16	0x1021	0xffff	0x0	0	0	0x29b1

Do the docs contain an error that has found its way into multiple tables of CRC polynomials?

I am trying to encode an uplink UM106MaintainSpeed message using the following sample code

#include <stdint.h>
#include <string.h>
#include <math.h>
#include <libacars/asn1/FANSATCUplinkMessage.h>
#include <libacars/asn1/FANSATCUplinkMsgElementId.h>
#include <libacars/asn1/FANSATCUplinkMsgElementIdSequence.h>
#include <libacars/asn1/FANSSpeed.h>
#include <libacars/libacars.h>
#include <libacars/cpdlc.h>


void build() {
    FANSATCUplinkMessage_t um;
    um.aTCMessageheader.msgIdentificationNumber = 15;
    um.aTCMessageheader.msgReferenceNumber = NULL;
    um.aTCMessageheader.timestamp->hours = 9;
    um.aTCMessageheader.timestamp->minutes = 25;
    um.aTCMessageheader.timestamp->seconds = 35;
    um.aTCuplinkmsgelementId.present = FANSATCUplinkMsgElementId_PR_uM106Speed,
    um.aTCuplinkmsgelementId.choice.uM106Speed.present = FANSSpeed_PR_speedIndicated;
    um.aTCuplinkmsgelementId.choice.uM106Speed.choice.speedIndicated = 200;
    um.aTCuplinkmsgelementid_seqOf = NULL;

    la_proto_node *node = la_proto_node_new();
    //LA_NEW(la_cpdlc_msg, msg);
    la_cpdlc_msg msg;
    msg.data = &um;
    node->data = &msg;
    node->td = &la_DEF_cpdlc_message;
    msg.asn_type = &asn_DEF_FANSATCUplinkMessage;

    unsigned char output[50];
    uper_encode_to_buffer(&asn_DEF_FANSATCUplinkMessage, node, output, 50);
}

int main(int argc, char **argv) {
    build();
}

I added this file to the examples directory and updated the CMakeLists.txt EXAMPLE_BINARIES set

I get the following compile error when running make

MakeFiles/cpdlc_maintain_speed.dir/cpdlc_maintain_speed.c.o: In function `build':
cpdlc_maintain_speed.c:(.text+0x8a): undefined reference to `asn_DEF_FANSATCUplinkMessage'
cpdlc_maintain_speed.c:(.text+0xa4): undefined reference to `asn_DEF_FANSATCUplinkMessage'
cpdlc_maintain_speed.c:(.text+0xb0): undefined reference to `uper_encode_to_buffer'
collect2: error: ld returned 1 exit status
make[2]: *** [examples/cpdlc_maintain_speed] Error 1
make[1]: *** [examples/CMakeFiles/cpdlc_maintain_speed.dir/all] Error 2
make: *** [all] Error 2

Are there other changes needed to be made to build this code ?

Hi,
A nice additional feature would be if libacars could automatic assemble CPDLC messages / replace the placeholders, eg.:
REQUEST DIRECT TO [position] => REQUEST DIRECT TO GAMLI

Is something like this planned?

Thanks

Parsing of Media Advisory frame with 10 or more available link indicators results in unterminated string available_links in la_media_adv_msg struct (missing \0). This can lead to unexpected (and potentially funny) program behavior when the string is used later in the program.

For example, in decode_acars_apps it causes reading past end of the buffer, until next null character is found (which is at the end of text string). This results in parsing the whole message as letter codes of available links and printing them as a long list.

Example that illustrates the problem:

./decode_acars_apps d SA '0EV123456VVVVVVVVVV/HERE IS THE TEXT MESSAGE THAT IS NOT A LIST OF AVAILABLE LINKS'

Hi ,just tried your latest libacars.dll (1.2.0) in latest JAERO 1.0.4.10 and using I7 win10/64bit, JAERO runs fine decoding voice but shuts down after a couple of minutes decoding data, I am recieving L-band from Alphasat . I swopped out the libacars .dll with the previous version and JAERO runs constantly with no problems apart from no MIAM decodes.......sorry ...
Cheers
Dave G7gqw

These are general notes that could be added to the README.md file. They assume that the command line Xcode is setup; but not much else.

The cmake command is needed.

$ brew install cmake
Updating Homebrew...
...
==> Pouring cmake--3.20.2.big_sur.bottle.tar.gz
==> Summary
🍺  /usr/local/Cellar/cmake/3.20.2: 6,468 files, 69.6MB
...
$

Then the build is easy (as per the present README.md file).

$ git clone [email protected]:szpajder/libacars.git
Cloning into 'libacars'...
...
$ cd libacars/
$ mkdir build
$ cd build/
$ cmake ../
-- The C compiler identification is AppleClang 12.0.0.12000032
...
-- Found ZLIB: /Library/Developer/CommandLineTools/SDKs/MacOSX11.1.sdk/usr/lib/libz.tbd (found version "1.2.11")
-- Found LibXml2: /Library/Developer/CommandLineTools/SDKs/MacOSX11.1.sdk/usr/lib/libxml2.tbd (found version "2.9.4")
-- libacars configuration summary:
-- - zlib:              requested: ON, enabled: TRUE
-- - libxml2:           requested: ON, enabled: TRUE
-- Configuring done
-- Generating done
...
$ make
...
[100%] Built target decode_acars_apps
$

The install on a Mac does not need ldconfig. (dyld exists; but not needed).

$ sudo make install
Password: ...
...
Install the project...
...
-- Installing: /usr/local/lib/libacars-2.2.dylib
-- Installing: /usr/local/lib/libacars-2.dylib
...
$

Using the code in https://github.com/szpajder/libacars/blob/master/doc/PROG_GUIDE.md we can prove this install works.

$cat > /tmp/deacars.c 
...
^D
$ cc -o /tmp/deacars -L/usr/local/lib/ -I/usr/local/include/libacars-2 /tmp/deacars.c -lacars-2
$ /tmp/deacars
Decoded message:
ACARS:
 Reassembly: unknown
 Reg: .SP-LDE Flight: LO02DM
 Mode: 2 Label: 23 Blk id: 3 More: 0 Ack: ! Msg num: M09A
 Message:
  ONN01LO02DM/**292041ELLXEPWA20410028

$

Hope that helps. Thank you for the project.

i need the development package to compile a program and i need libacars.h

libacar call exit when compiled as shared lib. This is bad.

This library package calls exit() or _exit(), probably in a non-fork()
context. Doing so from a library is strongly discouraged - when a library
function calls exit(), it prevents the calling program from handling the
error, reporting it to the user, closing files properly, and cleaning up any
state that the program has. It is preferred for the library to return an
actual error code and let the calling program decide how to handle the
situation.

Please correct it.

Some ACARS packets, specifically ones with H1 labels, should have sub labels. Add support for decoding and storing the sub label.

(See: http://www.cosmic.com.au/acarsanalyser/v3/DataRes/MsgLabelsData.asp#sublabel for examples of sub labels)

pkg_check_modules(LIBACARS libacars-2>=2.0.0) not detects compiled library from stable release.

By parsing Media Advisory frame with text message longer than 254 characters, it is possible to overflow text buffer in la_media_adv_msg leading to program crash or other insecure behavior.

The problem is caused by using strcpy() in la_media_adv_parse() without checking the size of input.

Example frame that triggers the buffer overflow:

d SA 0EV133800/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

This potentially may be exploited over radio link.

Hi,

First of all, thanks for your great work!

It seems that with the latest version(s) of libacars some messages that jaero attempts to decode are not decoded. When building and running against an older version of libacars they are correctly decoded. The messages that fail seem to be these that start with the "- #MD" token, for example this H1:

• #MD/A6 PIKCPYA.ADS.66168A07040B000C000D010E011000D9FB

When I strip off the first part of the message in jaero and pass "/PIKCPYA.ADS.66168A07040B000C000D010E011000D9FB" it works fine.
Now this is of course easy enough but since it seems this was not issue in earlier versions of libacars I just want to check with you if you think this needs to be done in jaero or if perhaps it is an issue in libacars.

Additionally, in longer messages, additional "- #MD" tokens can be found. I could only get these to decode by stripping away these tokens in jaero. Same question there I guess, should the client take care of stripping these off the message before attempting to decode?

Many thanks!

Jeroen

As this library grows and supports more message types, it might be nice to be able to go back to archived data and re-run a decoder on previously not-decoded messages (cf your comment about being "lazy" :) about AFN messages in the closed issue). What would you think about adding an archive output format that could "save" what has been demodulated for later analysis but an as-yet-unreleased decoder?

Hi,I found a reassemble bug Under specific condition.
Here is the example log

{"timestamp":1630031299.3498211,"station_id":"test-01","channel":1,"freq":127.275,"level":-11,"error":0,"mode":"2","label":"C1","block_id":"M","ack":false,"tail":"B-xxxx","text":"msg example 1-1","end":true,"assstat":"in progress"}
{"timestamp":1630031306.879694,"station_id":"test-01","channel":1,"freq":127.275,"level":-11,"error":0,"mode":"2","label":"C1","block_id":"N","ack":false,"tail":"B-xxxx","text":"msg example 1-2","end":true,"assstat":"in progress"}
{"timestamp":1630031314.1785741,"station_id":"test-01","channel":1,"freq":127.275,"level":-11,"error":0,"mode":"2","label":"C1","block_id":"O","ack":false,"tail":"B-5528","text":"msg example 1-3","end":true,"assstat":"in progress"}
{"timestamp":1630031320.9381371,"station_id":"test-01","channel":1,"freq":127.275,"level":-11,"error":0,"mode":"2","label":"A4","block_id":"P","ack":false,"tail":"B-xxxx","text":"/WUHDCYA.FS1/FSM 0228 210827 ZXXXX\r\nCXA1111 CDA REJECTED\r\nCLEARANCE CANCELLED\r\nREVERT TO VOICE PROCEDURES\r\n1A01","assstat":"skipped"}

not msg lost, another type msg(label A4) started at block_id P after msg block_id O (label C1),but label C1 series not finished at this time, but after block_id P send will be out of sequence from reassemble

{"timestamp":1630031327.961997,"station_id":"test-01","channel":1,"freq":127.275,"level":-11,"error":0,"mode":"2","label":"C1","block_id":"Q","ack":false,"tail":"B-xxxx","text":"msg example 1-4","end":true,"assstat":"out of sequence"}

now
static uint32_t acars_key_hash(void const *key) {
acars_key *k = (acars_key *)key;
uint32_t h = la_hash_string(k->addr, LA_HASH_INIT);
h = la_hash_string(k->label, h);
h = la_hash_string(k->msn, h);
return h;
}

but I can't remove label from the code. I think maybe libacars can add another one identifies to make sure to the address msg is continuously ,not require prev_seq_num is continuously.

thanks a lot.