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linux: cache netmask for accurate subnet prefix calculation to fix implementation which always returned 0 (#1155)

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Co-authored-by: Syed Amer Gilani <syed.gilani@trilux.com>
This commit is contained in:
Amer
2025-11-21 22:21:59 +01:00
committed by GitHub
parent af834c9fff
commit 94b267d67e
5 changed files with 188 additions and 14 deletions
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ports/linux/bip-init.c
+41 -14
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@@ -45,6 +45,8 @@ static uint16_t BIP_Port;
static struct in_addr BIP_Address;
/* IP broadcast address - stored here in network byte order */
static struct in_addr BIP_Broadcast_Addr;
/* IP netmask - stored here in network byte order */
static struct in_addr BIP_Netmask;
/* broadcast binding mechanism */
static bool BIP_Broadcast_Binding_Address_Override;
static struct in_addr BIP_Broadcast_Binding_Address;
@@ -233,9 +235,24 @@ bool bip_get_broadcast_addr(BACNET_IP_ADDRESS *addr)
*/
bool bip_set_subnet_prefix(uint8_t prefix)
{
/* not something we do within this driver */
(void)prefix;
return false;
uint32_t mask = 0;
if ((prefix == 0) || (prefix > 32)) {
return false;
}
mask = (prefix == 32) ? UINT32_MAX : (UINT32_MAX << (32 - prefix));
BIP_Netmask.s_addr = htonl(mask);
#if !defined(BACNET_IP_BROADCAST_USE_CLASSADDR)
if ((BIP_Address.s_addr != 0) && !BIP_Broadcast_Binding_Address_Override) {
uint32_t address = ntohl(BIP_Address.s_addr);
uint32_t broadcast = (address & mask) | (~mask);
BIP_Broadcast_Addr.s_addr = htonl(broadcast);
}
#endif
return true;
}
/**
@@ -244,21 +261,24 @@ bool bip_set_subnet_prefix(uint8_t prefix)
*/
uint8_t bip_get_subnet_prefix(void)
{
uint32_t address = 0;
uint32_t broadcast = 0;
uint32_t mask = 0xFFFFFFFE;
uint32_t mask = 0;
uint8_t prefix = 0;
address = BIP_Address.s_addr;
broadcast = BIP_Broadcast_Addr.s_addr;
/* calculate the subnet prefix from the broadcast address */
for (prefix = 1; prefix <= 32; prefix++) {
if ((address | mask) == broadcast) {
break;
}
mask = ntohl(BIP_Netmask.s_addr);
if (mask == 0) {
return 0;
}
while ((mask & 0x80000000) != 0) {
prefix++;
mask = mask << 1;
}
if (mask != 0) {
/* non-contiguous netmask */
return 0;
}
return prefix;
}
@@ -774,6 +794,13 @@ void bip_set_interface(const char *ifname)
fprintf(stderr, "BIP: Address: %s\n", inet_ntoa(local_address));
fflush(stderr);
}
/* cache interface netmask */
rv = bip_get_local_address_ioctl(ifname, &netmask, SIOCGIFNETMASK);
if (rv < 0) {
BIP_Netmask.s_addr = 0;
} else {
BIP_Netmask.s_addr = netmask.s_addr;
}
/* setup local broadcast address */
#ifdef BACNET_IP_BROADCAST_USE_CLASSADDR
long broadcast_address;
@@ -798,7 +825,6 @@ void bip_set_interface(const char *ifname)
}
BIP_Broadcast_Addr.s_addr = htonl(broadcast_address);
#else
rv = bip_get_local_address_ioctl(ifname, &netmask, SIOCGIFNETMASK);
if (rv < 0) {
BIP_Broadcast_Addr.s_addr = ~0;
} else {
@@ -980,6 +1006,7 @@ void bip_cleanup(void)
/* these were set non-zero during interface configuration */
BIP_Address.s_addr = 0;
BIP_Broadcast_Addr.s_addr = 0;
BIP_Netmask.s_addr = 0;
return;
}