pfSense

After a simple analysis, it seems that the problem is in the following code range. I suspect it is pfSense_interface_setaddress, because I used the subnet result of /30 to check ifconfig and found that /32 was allocated.

[22.01-RELEASE][root@pfSense.home.arpa]/var/log: ifconfig igb2
igb2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
description: IPLCWan
options=e527bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,WOL_MAGIC,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 00:25:90:ba:0f:f2
inet6 fe80::225:90ff:feba:ff2%igb2 prefixlen 64 scopeid 0x3
inet XXX.XXX.XXX.XXX netmask 0xffffffff broadcast XXX.XXX.XXX.XXX
inet XXX.XXX.XXX.XXX netmask 0xfffffffc broadcast XXX.XXX.XXX.XXX
media: Ethernet autoselect (1000baseT <full-duplex>)
status: active
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

[22.01-RELEASE][root@pfSense.home.arpa]/var/log: ifconfig igb2 inet XXX.XXX.XXX.XXX/30

[22.01-RELEASE][root@pfSense.home.arpa]/var/log: ifconfig igb2
igb2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
description: IPLCWan
options=e527bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,TSO6,LRO,WOL_MAGIC,VLAN_HWFILTER,VLAN_HWTSO,RXCSUM_IPV6,TXCSUM_IPV6>
ether 00:25:90:ba:0f:f2
inet6 fe80::225:90ff:feba:ff2%igb2 prefixlen 64 scopeid 0x3
inet XXX.XXX.XXX.XXX netmask 0xfffffffc broadcast XXX.XXX.XXX.XXX
inet XXX.XXX.XXX.XXX netmask 0xfffffffc broadcast XXX.XXX.XXX.XXX
media: Ethernet autoselect (1000baseT <full-duplex>)
status: active
nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>

switch ($wancfg['ipaddr']) {
        case 'dhcp':
            interface_dhcp_configure($interface);
            break;
        case 'pppoe':
        case 'l2tp':
        case 'pptp':
        case 'ppp':
            interface_ppps_configure($interface);
            break;
        default:
            /* XXX: Kludge for now related to #3280 */
            if (!in_array($tunnelif, array("gif", "gre", "ovp", "ips"))) {
                if (is_ipaddrv4($wancfg['ipaddr']) && $wancfg['subnet'] <> "") {
                    pfSense_interface_setaddress($realif, "{$wancfg['ipaddr']}/{$wancfg['subnet']}");
                }
            }
            break;
    }