Struct ResolverOpts

#[non_exhaustive]
pub struct ResolverOpts {

    pub ndots: usize,
    pub timeout: Duration,
    pub attempts: usize,
    pub check_names: bool,
    pub edns0: bool,
    pub validate: bool,
    pub ip_strategy: LookupIpStrategy,
    pub cache_size: usize,
    pub use_hosts_file: ResolveHosts,
    pub positive_min_ttl: Option<Duration>,
    pub negative_min_ttl: Option<Duration>,
    pub positive_max_ttl: Option<Duration>,
    pub negative_max_ttl: Option<Duration>,
    pub num_concurrent_reqs: usize,
    pub preserve_intermediates: bool,
    pub try_tcp_on_error: bool,
    pub server_ordering_strategy: ServerOrderingStrategy,
    pub recursion_desired: bool,
    pub avoid_local_udp_ports: Arc<HashSet<u16>>,
    pub os_port_selection: bool,
    pub case_randomization: bool,
    pub trust_anchor: Option<PathBuf>,
}

Configuration for the Resolver

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

ndots: usize

Sets the number of dots that must appear (unless it’s a final dot representing the root) before a query is assumed to include the TLD. The default is one, which means that www would never be assumed to be a TLD, and would always be appended to either the search

timeout: Duration

Specify the timeout for a request. Defaults to 5 seconds

attempts: usize

Number of retries after lookup failure before giving up. Defaults to 2

check_names: bool

Validate the names in the response, not implemented don’t really see the point unless you need to support badly configured DNS

edns0: bool

Enable edns, for larger records

validate: bool

Use DNSSEC to validate the request

ip_strategy: LookupIpStrategy

The ip_strategy for the Resolver to use when lookup Ipv4 or Ipv6 addresses

cache_size: usize

Cache size is in number of records (some records can be large)

use_hosts_file: ResolveHosts

Check /etc/hosts file before dns requery (only works for unix like OS)

positive_min_ttl: Option<Duration>

Optional minimum TTL for positive responses.

If this is set, any positive responses with a TTL lower than this value will have a TTL of positive_min_ttl instead. Otherwise, this will default to 0 seconds.

negative_min_ttl: Option<Duration>

Optional minimum TTL for negative (NXDOMAIN) responses.

If this is set, any negative responses with a TTL lower than this value will have a TTL of negative_min_ttl instead. Otherwise, this will default to 0 seconds.

positive_max_ttl: Option<Duration>

Optional maximum TTL for positive responses.

If this is set, any positive responses with a TTL higher than this value will have a TTL of positive_max_ttl instead. Otherwise, this will default to MAX_TTL seconds.

negative_max_ttl: Option<Duration>

Optional maximum TTL for negative (NXDOMAIN) responses.

If this is set, any negative responses with a TTL higher than this value will have a TTL of negative_max_ttl instead. Otherwise, this will default to MAX_TTL seconds.

num_concurrent_reqs: usize

Number of concurrent requests per query

Where more than one nameserver is configured, this configures the resolver to send queries to a number of servers in parallel. Defaults to 2; 0 or 1 will execute requests serially.

preserve_intermediates: bool

Preserve all intermediate records in the lookup response, such as CNAME records

try_tcp_on_error: bool

Try queries over TCP if they fail over UDP.

server_ordering_strategy: ServerOrderingStrategy

The server ordering strategy that the resolver should use.

recursion_desired: bool

Request upstream recursive resolvers to not perform any recursion.

This is true by default, disabling this is useful for requesting single records, but may prevent successful resolution.

avoid_local_udp_ports: Arc<HashSet<u16>>

Local UDP ports to avoid when making outgoing queries

os_port_selection: bool

Request UDP bind ephemeral ports directly from the OS

Boolean parameter to specify whether to use the operating system’s standard UDP port selection logic instead of Hickory’s logic to securely select a random source port. We do not recommend using this option unless absolutely necessary, as the operating system may select ephemeral ports from a smaller range than Hickory, which can make response poisoning attacks easier to conduct. Some operating systems (notably, Windows) might display a user-prompt to allow a Hickory-specified port to be used, and setting this option will prevent those prompts from being displayed. If os_port_selection is true, avoid_local_udp_ports will be ignored.

case_randomization: bool

Enable case randomization.

Randomize the case of letters in query names, and require that responses preserve the case of the query name, in order to mitigate spoofing attacks. This is only applied over UDP.

This implements the mechanism described in draft-vixie-dnsext-dns0x20-00.

trust_anchor: Option<PathBuf>

Path to a DNSSEC trust anchor file.

If this is provided, validate will automatically be set to true, enabling DNSSEC validation.

Trait Implementations

impl Clone for ResolverOpts

fn clone(&self) -> ResolverOpts

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ResolverOpts

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for ResolverOpts

fn default() -> ResolverOpts

Default values for the Resolver configuration.

This follows the resolv.conf defaults as defined in the Linux man pages