-- means using gethostbyname(2) and gethostbyaddr(2)
which usually call system's standard resolver of the host.
If RESOLV is not specified, "sys" is disabled if the IP-address of the
host of DeleGate is resolvable by "dns".
If empty value is specified as RESOLV="" then only hosts listed
in HOSTS parameter can be resolved (this could be useful
when you must hide hosts table for security consideration).
Each resolver can be specified with optional argument like follows:
DNS Routing:
A resolver can be applied to specific queries from specific clients.
The optional queryHostList specifies for which hosts or
addresses the resolver is applied.
The optional clientHostList specifies for which client hosts
the resolver is applied.
Example: selecting DNS servers depending on the inquired host/address
RESOLV="cache,dns:{192.168.1.2:8053}:{192.168.*,*.localdomain},dns:192.168.1.1"
// resolve local hosts with DNS sever at 192.168.1.2:8053
// and resolve others with 192.168.1.1:53
// this can be decomposed into a set of parameters like follows: RESOLV="cache,dns:local-dns:local-hosts,dns:192.168.1.1" HOSTLIST=local-dns:192.168.1.2:8053 HOSTLIST=local-hosts:192.168.*,*.localdomain
Example: selecting resolvers depending on the inquiring (client) DNS host
RESOLV="file:/etc/hosts:localHosts:192.168.*,dns:xx.xx.xx.xx" HOSTLIST="localHosts:192.168.*,*.localdomain,*.mydomain"
// queries from local hosts (192.168.*) for "localHosts" are resolved
// with the file "/etc/hosts", others are resolved with the DNS server
"xx.xx.xx.xx".
By default, a connection to a host which has multiple IP addresses
is tried for each address in the order they are defined in each
resolver. A special parameter HOSTS="*/*/RR" can be added to
specify "Round Robin" where those IP addresses are tried in
round robin order.