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interactive.c
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interactive.c
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// dump1090, a Mode S messages decoder for RTLSDR devices.
//
// Copyright (C) 2012 by Salvatore Sanfilippo <[email protected]>
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
#include "ppup1090.h"
//
// ============================= Utility functions ==========================
//
static uint64_t mstime(void) {
struct timeval tv;
uint64_t mst;
gettimeofday(&tv, NULL);
mst = ((uint64_t)tv.tv_sec)*1000;
mst += tv.tv_usec/1000;
return mst;
}
//
//=========================================================================
//
// Add a new DF structure to the interactive mode linked list
//
void interactiveCreateDF(struct aircraft *a, struct modesMessage *mm) {
struct stDF *pDF = (struct stDF *) malloc(sizeof(*pDF));
if (pDF) {
// Default everything to zero/NULL
memset(pDF, 0, sizeof(*pDF));
// Now initialise things
pDF->seen = a->seen;
pDF->llTimestamp = mm->timestampMsg;
pDF->addr = mm->addr;
pDF->pAircraft = a;
memcpy(pDF->msg, mm->msg, MODES_LONG_MSG_BYTES);
if (!pthread_mutex_lock(&Modes.pDF_mutex)) {
if ((pDF->pNext = Modes.pDF)) {
Modes.pDF->pPrev = pDF;
}
Modes.pDF = pDF;
pthread_mutex_unlock(&Modes.pDF_mutex);
} else {
free(pDF);
}
}
}
//
// Remove stale DF's from the interactive mode linked list
//
void interactiveRemoveStaleDF(time_t now) {
struct stDF *pDF = NULL;
struct stDF *prev = NULL;
// Only fiddle with the DF list if we gain possession of the mutex
// If we fail to get the mutex we'll get another chance to tidy the
// DF list in a second or so.
if (!pthread_mutex_trylock(&Modes.pDF_mutex)) {
pDF = Modes.pDF;
while(pDF) {
if ((now - pDF->seen) > Modes.interactive_delete_ttl) {
if (Modes.pDF == pDF) {
Modes.pDF = NULL;
} else {
prev->pNext = NULL;
}
// All DF's in the list from here onwards will be time
// expired, so delete them all
while (pDF) {
prev = pDF; pDF = pDF->pNext;
free(prev);
}
} else {
prev = pDF; pDF = pDF->pNext;
}
}
pthread_mutex_unlock (&Modes.pDF_mutex);
}
}
struct stDF *interactiveFindDF(uint32_t addr) {
struct stDF *pDF = NULL;
if (!pthread_mutex_lock(&Modes.pDF_mutex)) {
pDF = Modes.pDF;
while(pDF) {
if (pDF->addr == addr) {
pthread_mutex_unlock (&Modes.pDF_mutex);
return (pDF);
}
pDF = pDF->pNext;
}
pthread_mutex_unlock (&Modes.pDF_mutex);
}
return (NULL);
}
//
//========================= Interactive mode ===============================
//
// Return a new aircraft structure for the interactive mode linked list
// of aircraft
//
struct aircraft *interactiveCreateAircraft(struct modesMessage *mm) {
struct aircraft *a = (struct aircraft *) malloc(sizeof(*a));
// Default everything to zero/NULL
memset(a, 0, sizeof(*a));
// Now initialise things that should not be 0/NULL to their defaults
a->addr = mm->addr;
a->lat = a->lon = 0.0;
memset(a->signalLevel, mm->signalLevel, 8); // First time, initialise everything
// to the first signal strength
// mm->msgtype 32 is used to represent Mode A/C. These values can never change, so
// set them once here during initialisation, and don't bother to set them every
// time this ModeA/C is received again in the future
if (mm->msgtype == 32) {
int modeC = ModeAToModeC(mm->modeA | mm->fs);
a->modeACflags = MODEAC_MSG_FLAG;
if (modeC < -12) {
a->modeACflags |= MODEAC_MSG_MODEA_ONLY;
} else {
mm->altitude = modeC * 100;
mm->bFlags |= MODES_ACFLAGS_ALTITUDE_VALID;
}
}
return (a);
}
//
//=========================================================================
//
// Return the aircraft with the specified address, or NULL if no aircraft
// exists with this address.
//
struct aircraft *interactiveFindAircraft(uint32_t addr) {
struct aircraft *a = Modes.aircrafts;
while(a) {
if (a->addr == addr) return (a);
a = a->next;
}
return (NULL);
}
//
//=========================================================================
//
// We have received a Mode A or C response.
//
// Search through the list of known Mode-S aircraft and tag them if this Mode A/C
// matches their known Mode S Squawks or Altitudes(+/- 50feet).
//
// A Mode S equipped aircraft may also respond to Mode A and Mode C SSR interrogations.
// We can't tell if this is a Mode A or C, so scan through the entire aircraft list
// looking for matches on Mode A (squawk) and Mode C (altitude). Flag in the Mode S
// records that we have had a potential Mode A or Mode C response from this aircraft.
//
// If an aircraft responds to Mode A then it's highly likely to be responding to mode C
// too, and vice verca. Therefore, once the mode S record is tagged with both a Mode A
// and a Mode C flag, we can be fairly confident that this Mode A/C frame relates to that
// Mode S aircraft.
//
// Mode C's are more likely to clash than Mode A's; There could be several aircraft
// cruising at FL370, but it's less likely (though not impossible) that there are two
// aircraft on the same squawk. Therefore, give precidence to Mode A record matches
//
// Note : It's theoretically possible for an aircraft to have the same value for Mode A
// and Mode C. Therefore we have to check BOTH A AND C for EVERY S.
//
void interactiveUpdateAircraftModeA(struct aircraft *a) {
struct aircraft *b = Modes.aircrafts;
while(b) {
if ((b->modeACflags & MODEAC_MSG_FLAG) == 0) {// skip any fudged ICAO records
// If both (a) and (b) have valid squawks...
if ((a->bFlags & b->bFlags) & MODES_ACFLAGS_SQUAWK_VALID) {
// ...check for Mode-A == Mode-S Squawk matches
if (a->modeA == b->modeA) { // If a 'real' Mode-S ICAO exists using this Mode-A Squawk
b->modeAcount = a->messages;
b->modeACflags |= MODEAC_MSG_MODEA_HIT;
a->modeACflags |= MODEAC_MSG_MODEA_HIT;
if ( (b->modeAcount > 0) &&
( (b->modeCcount > 1)
|| (a->modeACflags & MODEAC_MSG_MODEA_ONLY)) ) // Allow Mode-A only matches if this Mode-A is invalid Mode-C
{a->modeACflags |= MODEAC_MSG_MODES_HIT;} // flag this ModeA/C probably belongs to a known Mode S
}
}
// If both (a) and (b) have valid altitudes...
if ((a->bFlags & b->bFlags) & MODES_ACFLAGS_ALTITUDE_VALID) {
// ... check for Mode-C == Mode-S Altitude matches
if ( (a->modeC == b->modeC ) // If a 'real' Mode-S ICAO exists at this Mode-C Altitude
|| (a->modeC == b->modeC + 1) // or this Mode-C - 100 ft
|| (a->modeC + 1 == b->modeC ) ) { // or this Mode-C + 100 ft
b->modeCcount = a->messages;
b->modeACflags |= MODEAC_MSG_MODEC_HIT;
a->modeACflags |= MODEAC_MSG_MODEC_HIT;
if ( (b->modeAcount > 0) &&
(b->modeCcount > 1) )
{a->modeACflags |= (MODEAC_MSG_MODES_HIT | MODEAC_MSG_MODEC_OLD);} // flag this ModeA/C probably belongs to a known Mode S
}
}
}
b = b->next;
}
}
//
//=========================================================================
//
void interactiveUpdateAircraftModeS() {
struct aircraft *a = Modes.aircrafts;
while(a) {
int flags = a->modeACflags;
if (flags & MODEAC_MSG_FLAG) { // find any fudged ICAO records
// clear the current A,C and S hit bits ready for this attempt
a->modeACflags = flags & ~(MODEAC_MSG_MODEA_HIT | MODEAC_MSG_MODEC_HIT | MODEAC_MSG_MODES_HIT);
interactiveUpdateAircraftModeA(a); // and attempt to match them with Mode-S
}
a = a->next;
}
}
//
//=========================================================================
//
// Receive new messages and populate the interactive mode with more info
//
struct aircraft *interactiveReceiveData(struct modesMessage *mm) {
struct aircraft *a, *aux;
// Return if (checking crc) AND (not crcok) AND (not fixed)
if (mm->crcok == 0)
return NULL;
// Lookup our aircraft or create a new one
a = interactiveFindAircraft(mm->addr);
if (!a) { // If it's a currently unknown aircraft....
a = interactiveCreateAircraft(mm); // ., create a new record for it,
a->next = Modes.aircrafts; // .. and put it at the head of the list
Modes.aircrafts = a;
} else {
/* If it is an already known aircraft, move it on head
* so we keep aircrafts ordered by received message time.
*
* However move it on head only if at least one second elapsed
* since the aircraft that is currently on head sent a message,
* othewise with multiple aircrafts at the same time we have an
* useless shuffle of positions on the screen. */
if (0 && Modes.aircrafts != a && (time(NULL) - a->seen) >= 1) {
aux = Modes.aircrafts;
while(aux->next != a) aux = aux->next;
/* Now we are a node before the aircraft to remove. */
aux->next = aux->next->next; /* removed. */
/* Add on head */
a->next = Modes.aircrafts;
Modes.aircrafts = a;
}
}
a->signalLevel[a->messages & 7] = mm->signalLevel;// replace the 8th oldest signal strength
a->seen = time(NULL);
a->timestamp = mm->timestampMsg;
a->messages++;
// If a (new) CALLSIGN has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_CALLSIGN_VALID) {
memcpy(a->flight, mm->flight, sizeof(a->flight));
}
// If a (new) ALTITUDE has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_ALTITUDE_VALID) {
if ( (a->modeCcount) // if we've a modeCcount already
&& (a->altitude != mm->altitude ) ) // and Altitude has changed
// && (a->modeC != mm->modeC + 1) // and Altitude not changed by +100 feet
// && (a->modeC + 1 != mm->modeC ) ) // and Altitude not changes by -100 feet
{
a->modeCcount = 0; //....zero the hit count
a->modeACflags &= ~MODEAC_MSG_MODEC_HIT;
}
a->altitude = mm->altitude;
a->modeC = (mm->altitude + 49) / 100;
}
// If a (new) SQUAWK has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_SQUAWK_VALID) {
if (a->modeA != mm->modeA) {
a->modeAcount = 0; // Squawk has changed, so zero the hit count
a->modeACflags &= ~MODEAC_MSG_MODEA_HIT;
}
a->modeA = mm->modeA;
}
// If a (new) HEADING has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_HEADING_VALID) {
a->track = mm->heading;
}
// If a (new) SPEED has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_SPEED_VALID) {
a->speed = mm->velocity;
}
// If a (new) Vertical Descent rate has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_VERTRATE_VALID) {
a->vert_rate = mm->vert_rate;
}
// if the Aircraft has landed or taken off since the last message, clear the even/odd CPR flags
if ((mm->bFlags & MODES_ACFLAGS_AOG_VALID) && ((a->bFlags ^ mm->bFlags) & MODES_ACFLAGS_AOG)) {
a->bFlags &= ~(MODES_ACFLAGS_LLBOTH_VALID | MODES_ACFLAGS_AOG);
}
// If we've got a new cprlat or cprlon
if (mm->bFlags & MODES_ACFLAGS_LLEITHER_VALID) {
int location_ok = 0;
if (mm->bFlags & MODES_ACFLAGS_LLODD_VALID) {
a->odd_cprlat = mm->raw_latitude;
a->odd_cprlon = mm->raw_longitude;
a->odd_cprtime = mstime();
} else {
a->even_cprlat = mm->raw_latitude;
a->even_cprlon = mm->raw_longitude;
a->even_cprtime = mstime();
}
// If we have enough recent data, try global CPR
if (((mm->bFlags | a->bFlags) & MODES_ACFLAGS_LLEITHER_VALID) == MODES_ACFLAGS_LLBOTH_VALID && abs((int)(a->even_cprtime - a->odd_cprtime)) <= 10000) {
if (decodeCPR(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG)) == 0) {
location_ok = 1;
}
}
// Otherwise try relative CPR.
if (!location_ok && decodeCPRrelative(a, (mm->bFlags & MODES_ACFLAGS_LLODD_VALID), (mm->bFlags & MODES_ACFLAGS_AOG)) == 0) {
location_ok = 1;
}
//If we sucessfully decoded, back copy the results to mm so that we can print them in list output
if (location_ok) {
mm->bFlags |= MODES_ACFLAGS_LATLON_VALID;
mm->fLat = a->lat;
mm->fLon = a->lon;
}
}
// Update the aircrafts a->bFlags to reflect the newly received mm->bFlags;
a->bFlags |= mm->bFlags;
if (mm->msgtype == 32) {
int flags = a->modeACflags;
if ((flags & (MODEAC_MSG_MODEC_HIT | MODEAC_MSG_MODEC_OLD)) == MODEAC_MSG_MODEC_OLD) {
//
// This Mode-C doesn't currently hit any known Mode-S, but it used to because MODEAC_MSG_MODEC_OLD is
// set So the aircraft it used to match has either changed altitude, or gone out of our receiver range
//
// We've now received this Mode-A/C again, so it must be a new aircraft. It could be another aircraft
// at the same Mode-C altitude, or it could be a new airctraft with a new Mods-A squawk.
//
// To avoid masking this aircraft from the interactive display, clear the MODEAC_MSG_MODES_OLD flag
// and set messages to 1;
//
a->modeACflags = flags & ~MODEAC_MSG_MODEC_OLD;
a->messages = 1;
}
}
// If we are Logging DF's, and it's not a Mode A/C
if ( (mm->msgtype < 32)
|| (a->messages > 15) ) {
interactiveCreateDF(a,mm);
}
return (a);
}
//
//=========================================================================
//
// When in interactive mode If we don't receive new nessages within
// MODES_INTERACTIVE_DELETE_TTL seconds we remove the aircraft from the list.
//
void interactiveRemoveStaleAircrafts(void) {
struct aircraft *a = Modes.aircrafts;
struct aircraft *prev = NULL;
time_t now = time(NULL);
// Only do cleanup once per second
if (Modes.last_cleanup_time != now) {
Modes.last_cleanup_time = now;
interactiveRemoveStaleDF(now);
while(a) {
if ((now - a->seen) > Modes.interactive_delete_ttl) {
// Remove the element from the linked list, with care
// if we are removing the first element
if (!prev) {
Modes.aircrafts = a->next; free(a); a = Modes.aircrafts;
} else {
prev->next = a->next; free(a); a = prev->next;
}
} else {
prev = a; a = a->next;
}
}
}
}
//
//=========================================================================
//