Crate trust_dns_resolver
source · [−]Expand description
The Resolver is responsible for performing recursive queries to lookup domain names.
This is a 100% in process DNS resolver. It does not use the Host OS’ resolver. If what is
desired is to use the Host OS’ resolver, generally in the system’s libc, then the
std::net::ToSocketAddrs
variant over &str
should be used.
Unlike the trust-dns-client
, this tries to provide a simpler interface to perform DNS
queries. For update options, i.e. Dynamic DNS, the trust-dns-client
crate must be used
instead. The Resolver library is capable of searching multiple domains (this can be disabled by
using an FQDN during lookup), dual-stack IPv4/IPv6 lookups, performing chained CNAME lookups,
and features connection metric tracking for attempting to pick the best upstream DNS resolver.
There are two types for performing DNS queries, Resolver
and AsyncResolver
. Resolver
is the easiest to work with, it is a wrapper around AsyncResolver
. AsyncResolver
is a
Tokio
based async resolver, and can be used inside any Tokio
based system.
This as best as possible attempts to abide by the DNS RFCs, please file issues at https://github.com/bluejekyll/trust-dns.
Usage
Declare dependency
[dependency]
trust-dns-resolver = "*"
Using the Synchronous Resolver
This uses the default configuration, which sets the Google Public DNS as the upstream resolvers. Please see their privacy statement for important information about what they track, many ISP’s track similar information in DNS.
use std::net::*;
use trust_dns_resolver::Resolver;
use trust_dns_resolver::config::*;
// Construct a new Resolver with default configuration options
let resolver = Resolver::new(ResolverConfig::default(), ResolverOpts::default()).unwrap();
// Lookup the IP addresses associated with a name.
// The final dot forces this to be an FQDN, otherwise the search rules as specified
// in `ResolverOpts` will take effect. FQDN's are generally cheaper queries.
let response = resolver.lookup_ip("www.example.com.").unwrap();
// There can be many addresses associated with the name,
// this can return IPv4 and/or IPv6 addresses
let address = response.iter().next().expect("no addresses returned!");
if address.is_ipv4() {
assert_eq!(address, IpAddr::V4(Ipv4Addr::new(93, 184, 216, 34)));
} else {
assert_eq!(address, IpAddr::V6(Ipv6Addr::new(0x2606, 0x2800, 0x220, 0x1, 0x248, 0x1893, 0x25c8, 0x1946)));
}
Using the host system config
On Unix systems, the /etc/resolv.conf
can be used for configuration. Not all options
specified in the host systems resolv.conf
are applicable or compatible with this software. In
addition there may be additional options supported which the host system does not. Example:
// Use the host OS'es `/etc/resolv.conf`
let resolver = Resolver::from_system_conf().unwrap();
let response = resolver.lookup_ip("www.example.com.").unwrap();
Using the Tokio/Async Resolver
For more advanced asynchronous usage, the AsyncResolver
] is integrated with Tokio. In fact,
the AsyncResolver
is used by the synchronous Resolver for all lookups.
use std::net::*;
use tokio::runtime::Runtime;
use trust_dns_resolver::TokioAsyncResolver;
use trust_dns_resolver::config::*;
// We need a Tokio Runtime to run the resolver
// this is responsible for running all Future tasks and registering interest in IO channels
let mut io_loop = Runtime::new().unwrap();
// Construct a new Resolver with default configuration options
let resolver = io_loop.block_on(async {
TokioAsyncResolver::tokio(
ResolverConfig::default(),
ResolverOpts::default())
}).expect("failed to connect resolver");
// Lookup the IP addresses associated with a name.
// This returns a future that will lookup the IP addresses, it must be run in the Core to
// to get the actual result.
let lookup_future = resolver.lookup_ip("www.example.com.");
// Run the lookup until it resolves or errors
let mut response = io_loop.block_on(lookup_future).unwrap();
// There can be many addresses associated with the name,
// this can return IPv4 and/or IPv6 addresses
let address = response.iter().next().expect("no addresses returned!");
if address.is_ipv4() {
assert_eq!(address, IpAddr::V4(Ipv4Addr::new(93, 184, 216, 34)));
} else {
assert_eq!(address, IpAddr::V6(Ipv6Addr::new(0x2606, 0x2800, 0x220, 0x1, 0x248, 0x1893, 0x25c8, 0x1946)));
}
Generally after a lookup in an asynchronous context, there would probably be a connection made to a server, for example:
let ips = io_loop.block_on(resolver.lookup_ip("www.example.com.")).unwrap();
let result = io_loop.block_on(async {
let ip = ips.iter().next().unwrap();
TcpStream::connect((ip, 443))
})
.and_then(|conn| Ok(conn) /* do something with the connection... */)
.unwrap();
It’s beyond the scope of these examples to show how to deal with connection failures and
looping etc. But if you wanted to say try a different address from the result set after a
connection failure, it will be necessary to create a type that implements the Future
trait.
Inside the Future::poll
method would be the place to implement a loop over the different IP
addresses.
DNS-over-TLS and DNS-over-HTTPS
DNS-over-TLS and DNS-over-HTTPS are supported in the Trust-DNS Resolver library. The underlying implementations are available as addon libraries. WARNING The trust-dns developers make no claims on the security and/or privacy guarantees of this implementation.
To use DNS-over-TLS one of the dns-over-tls
features must be enabled at compile time. There
are three: dns-over-openssl
, dns-over-native-tls
, and dns-over-rustls
. For DNS-over-HTTPS
only rustls is supported with the dns-over-https-rustls
, this implicitly enables support for
DNS-over-TLS as well. The reason for each is to make the Trust-DNS libraries flexible for
different deployments, and/or security concerns. The easiest to use will generally be
dns-over-rustls
which utilizes the *ring*
Rust cryptography library (a rework of the
boringssl
project), this should compile and be usable on most ARM and x86 platforms.
dns-over-native-tls
will utilize the hosts TLS implementation where available or fallback to
openssl
where not supported. dns-over-openssl
will specify that openssl
should be used
(which is a perfectly fine option if required). If more than one is specified, the precedence
will be in this order (i.e. only one can be used at a time) dns-over-rustls
,
dns-over-native-tls
, and then dns-over-openssl
. NOTICE the trust-dns developers are not
responsible for any choice of library that does not meet required security requirements.
Example
Enable the TLS library through the dependency on trust-dns-resolver
:
trust-dns-resolver = { version = "*", features = ["dns-over-rustls"] }
A default TLS configuration is available for Cloudflare’s 1.1.1.1
DNS service (Quad9 as
well):
use trust_dns_resolver::Resolver;
use trust_dns_resolver::config::*;
// Construct a new Resolver with default configuration options
let mut resolver = Resolver::new(ResolverConfig::cloudflare_tls(), ResolverOpts::default()).unwrap();
// see example above...
mDNS (multicast DNS)
Multicast DNS is an experimental feature in Trust-DNS at the moment. Its support on different
platforms is not yet ideal. Initial support is only for IPv4 mDNS, as there are some
complexities to figure out with IPv6. Once enabled, an mDNS NameServer
will automatically be
added to the Resolver
and used for any lookups performed in the .local.
zone.
Re-exports
pub extern crate trust_dns_proto as proto;
Modules
Caching related functionality for the Resolver.
Configuration for a resolver
Error types for the crate
Lookup result from a resolution of ipv4 and ipv6 records with a Resolver.
LookupIp result from a resolution of ipv4 and ipv6 records with a Resolver.
System configuration loading
testing
Unit tests compatible with different runtime.
Structs
An asynchronous resolver for DNS generic over async Runtimes.
Configuration for the local hosts file
A domain name
The Resolver is used for performing DNS queries.
Traits
A type to allow for custom ConnectionProviders. Needed mainly for mocking purposes.
Conversion into a Name
Types of this trait will can be attempted for conversion to an IP address
Functions
returns a version as specified in Cargo.toml
Type Definitions
This is an alias for AsyncResolver
, which replaced the type previously
called ResolverFuture
.
tokio-runtime
An AsyncResolver used with Tokio