Access to DNS takes place using the software package openNet Server V21.0, which contains SOCKETS(BS2000) V21.0, using the Light Weight RESolver Daemon (LWRESD) program on the basis of the software package bind9.x (see the “BCAM Volume 1/2” manual).
SOCKETS(BS2000) V21.0 establishes the connection to LWRESD using an integrated LWRES client.
If DNS does not provide any corresponding information for the DNS information function which is called, an attempt is made to obtain this information from the BCAM transport system.
This applies both for implementing host names and for the FQDN (Fully Qualified Domain Name).
In the standard configuration the LWRESD is reachable under the local loopback address and port 921.
For a workaround made necessary for production reasons or for an additional special local private DNS configuration, it may be necessary to start a second LWRESD in parallel mode.This is achieved with an additional SCOPE command operand in the relevant administration commands for the LWRESD (see the manual “BCAM Volume 1/2”).
The values for the SCOPE operand are:
*STD: | The default setting; there is only one LWRESD; or the standard LWRESD is selected. |
*LWRES-NAS | Workaround for a second LWRESD which is addressed with the loopback address and the standard port 921. |
*LOCAL-DNS | Selection of a second LWRESD which communicates with a DNS server for a special local network (full support only in openNet Server > V3.6). |
If two LWRESDs are active, these must be reachable via different addreses and/or ports.
To be able to offer noew configuration options with one LWRESD, the selection of the possible keywords in the LWRESD configuration file SYSDAT.LWRESD.nnn.RESOLV.CONF has been extended. nnn is the LWRESD version, the current one being 210.
The additional keywords are:
lwserver IPv4 or IPv6 address
The list socket of the LWRESD is opened under this address so that it can be reached by the LWRES client.
lwlport port number
The list socket of the LWRESD is opened under this port number.
destport port number
A port deviating from the standard port number 53 can be specified for the entered name servers here. This enables tests of name servers which were started for this purpose under a non-standard port number.
Changes under lwserver, lwlport or destport cannot be enabled dynamically by reading in the LWRESD configuration file again (RELOAD-LWRESD command).
An LWRESD reboot is required, which can be initiated with the command sequence STOP-LWRESD and START-LWRESD or with the RESTART-LWRESD command.
The IPv4 or IPv6 address and the UDP port under which the selected LWRESD can be reached are stored in BCAM and can be read out or modified using the BCAM commands SHOW-DNS-ACCESS and MODIFY-DNS-ACCESS. This data is used starting with the next DNS access of SOCKETS(BS2000). It is no longer necessary to reboot SOCK-ETS(BS2000) after modifying the address.
The getsockopt() / setsockopt() subfunctions SO_LWRESDINFO; SO_LWADDR; SO_LWADACT enable a sockets program to test an LWRESD other than that configured.