Crate libp2p_dns

source ·
Expand description

DNS name resolution

Transport for libp2p.

This crate provides the type GenDnsConfig with its instantiations [DnsConfig] and TokioDnsConfig for use with async-std and tokio, respectively.

A GenDnsConfig is an address-rewriting Transport wrapper around an inner Transport. The composed transport behaves like the inner transport, except that Transport::dial resolves /dns/..., /dns4/..., /dns6/... and /dnsaddr/... components of the given Multiaddr through a DNS, replacing them with the resolved protocols (typically TCP/IP).

The async-std feature and hence the DnsConfig are enabled by default. Tokio users can furthermore opt-in to the tokio-dns-over-rustls and tokio-dns-over-https-rustls features. For more information about these features, please refer to the documentation of trust-dns-resolver.

On Unix systems, if no custom configuration is given, trust-dns-resolver will try to parse the /etc/resolv.conf file. This approach comes with a few caveats to be aware of:

  1. This fails (panics even!) if /etc/resolv.conf does not exist. This is the case on all versions of Android.
  2. DNS configuration is only evaluated during startup. Runtime changes are thus ignored.
  3. DNS resolution is obviously done in process and consequently not using any system APIs (like libc’s gethostbyname). Again this is problematic on platforms like Android, where there’s a lot of complexity hidden behind the system APIs. If the implementation requires different characteristics, one should consider providing their own implementation of GenDnsConfig or use platform specific APIs to extract the host’s DNS configuration (if possible) and provide a custom ResolverConfig.

Structs

GenDnsConfig
A Transport wrapper for performing DNS lookups when dialing Multiaddresses.
ResolveError
The error type for errors that get returned in the crate
ResolverConfig
Configuration for the upstream nameservers to use for resolution
ResolverOpts
Configuration for the Resolver

Enums

DnsErr
The possible errors of a GenDnsConfig wrapped transport.
ResolveErrorKind
The error kind for errors that get returned in the crate

Type Definitions

TokioDnsConfig
A Transport wrapper for performing DNS lookups when dialing Multiaddresses using tokio for all async I/O.