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Avoid false positives for address 000000 in the icao filter hashtable

This commit is contained in:
Oliver Jowett 2020-10-08 19:30:06 +08:00
parent 66f26846b8
commit f0055c978d
1 changed files with 16 additions and 14 deletions
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30
icao_filter.c
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@ -35,6 +35,8 @@ static uint32_t icao_filter_a[ICAO_FILTER_SIZE];
static uint32_t icao_filter_b[ICAO_FILTER_SIZE]; static uint32_t icao_filter_b[ICAO_FILTER_SIZE];
static uint32_t *icao_filter_active; static uint32_t *icao_filter_active;
#define EMPTY 0xFFFFFFFF
static uint32_t icaoHash(uint32_t a) static uint32_t icaoHash(uint32_t a)
{ {
// Jenkins one-at-a-time hash, unrolled for 3 bytes // Jenkins one-at-a-time hash, unrolled for 3 bytes
@ -61,8 +63,8 @@ static uint32_t icaoHash(uint32_t a)
void icaoFilterInit() void icaoFilterInit()
{ {
memset(icao_filter_a, 0, sizeof(icao_filter_a)); memset(icao_filter_a, 0xFF, sizeof(icao_filter_a));
memset(icao_filter_b, 0, sizeof(icao_filter_b)); memset(icao_filter_b, 0xFF, sizeof(icao_filter_b));
icao_filter_active = icao_filter_a; icao_filter_active = icao_filter_a;
} }
@ -70,26 +72,26 @@ void icaoFilterAdd(uint32_t addr)
{ {
uint32_t h, h0; uint32_t h, h0;
h0 = h = icaoHash(addr); h0 = h = icaoHash(addr);
while (icao_filter_active[h] && icao_filter_active[h] != addr) { while (icao_filter_active[h] != EMPTY && icao_filter_active[h] != addr) {
h = (h+1) & (ICAO_FILTER_SIZE-1); h = (h+1) & (ICAO_FILTER_SIZE-1);
if (h == h0) { if (h == h0) {
fprintf(stderr, "ICAO hash table full, increase ICAO_FILTER_SIZE\n"); fprintf(stderr, "ICAO hash table full, increase ICAO_FILTER_SIZE\n");
return; return;
} }
} }
if (!icao_filter_active[h]) if (icao_filter_active[h] == EMPTY)
icao_filter_active[h] = addr; icao_filter_active[h] = addr;
// also add with a zeroed top byte, for handling DF20/21 with Data Parity // also add with a zeroed top byte, for handling DF20/21 with Data Parity
h0 = h = icaoHash(addr & 0x00ffff); h0 = h = icaoHash(addr & 0x00ffff);
while (icao_filter_active[h] && (icao_filter_active[h] & 0x00ffff) != (addr & 0x00ffff)) { while (icao_filter_active[h] != EMPTY && (icao_filter_active[h] & 0x00ffff) != (addr & 0x00ffff)) {
h = (h+1) & (ICAO_FILTER_SIZE-1); h = (h+1) & (ICAO_FILTER_SIZE-1);
if (h == h0) { if (h == h0) {
fprintf(stderr, "ICAO hash table full, increase ICAO_FILTER_SIZE\n"); fprintf(stderr, "ICAO hash table full, increase ICAO_FILTER_SIZE\n");
return; return;
} }
} }
if (!icao_filter_active[h]) if (icao_filter_active[h] == EMPTY)
icao_filter_active[h] = addr; icao_filter_active[h] = addr;
} }
@ -98,7 +100,7 @@ int icaoFilterTest(uint32_t addr)
uint32_t h, h0; uint32_t h, h0;
h0 = h = icaoHash(addr); h0 = h = icaoHash(addr);
while (icao_filter_a[h] && icao_filter_a[h] != addr) { while (icao_filter_a[h] != EMPTY && icao_filter_a[h] != addr) {
h = (h+1) & (ICAO_FILTER_SIZE-1); h = (h+1) & (ICAO_FILTER_SIZE-1);
if (h == h0) if (h == h0)
break; break;
@ -107,7 +109,7 @@ int icaoFilterTest(uint32_t addr)
return 1; return 1;
h = h0; h = h0;
while (icao_filter_b[h] && icao_filter_b[h] != addr) { while (icao_filter_b[h] != EMPTY && icao_filter_b[h] != addr) {
h = (h+1) & (ICAO_FILTER_SIZE-1); h = (h+1) & (ICAO_FILTER_SIZE-1);
if (h == h0) if (h == h0)
break; break;
@ -124,21 +126,21 @@ uint32_t icaoFilterTestFuzzy(uint32_t partial)
partial &= 0x00ffff; partial &= 0x00ffff;
h0 = h = icaoHash(partial); h0 = h = icaoHash(partial);
while (icao_filter_a[h] && (icao_filter_a[h] & 0x00ffff) != partial) { while (icao_filter_a[h] != EMPTY && (icao_filter_a[h] & 0x00ffff) != partial) {
h = (h+1) & (ICAO_FILTER_SIZE-1); h = (h+1) & (ICAO_FILTER_SIZE-1);
if (h == h0) if (h == h0)
break; break;
} }
if ((icao_filter_a[h] & 0x00ffff) == partial) if (icao_filter_a[h] != EMPTY && (icao_filter_a[h] & 0x00ffff) == partial)
return icao_filter_a[h]; return icao_filter_a[h];
h = h0; h = h0;
while (icao_filter_b[h] && (icao_filter_b[h] & 0x00ffff) != partial) { while (icao_filter_b[h] != EMPTY && (icao_filter_b[h] & 0x00ffff) != partial) {
h = (h+1) & (ICAO_FILTER_SIZE-1); h = (h+1) & (ICAO_FILTER_SIZE-1);
if (h == h0) if (h == h0)
break; break;
} }
if ((icao_filter_b[h] & 0x00ffff) == partial) if (icao_filter_b[h] != EMPTY && (icao_filter_b[h] & 0x00ffff) == partial)
return icao_filter_b[h]; return icao_filter_b[h];
return 0; return 0;
@ -152,10 +154,10 @@ void icaoFilterExpire()
if (now >= next_flip) { if (now >= next_flip) {
if (icao_filter_active == icao_filter_a) { if (icao_filter_active == icao_filter_a) {
memset(icao_filter_b, 0, sizeof(icao_filter_b)); memset(icao_filter_b, 0xFF, sizeof(icao_filter_b));
icao_filter_active = icao_filter_b; icao_filter_active = icao_filter_b;
} else { } else {
memset(icao_filter_a, 0, sizeof(icao_filter_a)); memset(icao_filter_a, 0xFF, sizeof(icao_filter_a));
icao_filter_active = icao_filter_a; icao_filter_active = icao_filter_a;
} }
next_flip = now + MODES_ICAO_FILTER_TTL; next_flip = now + MODES_ICAO_FILTER_TTL;