https://github.com/aojea/mem-resolver

memresolver is an in-memory golang resolver that allows to override current golang Lookup func literals
https://github.com/aojea/mem-resolver

dns golang network resolver

Last synced: 18 days ago
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memresolver is an in-memory golang resolver that allows to override current golang Lookup func literals

• Host: GitHub
• URL: https://github.com/aojea/mem-resolver
• Owner: aojea
• License: apache-2.0
• Created: 2021-09-28T10:13:59.000Z (about 3 years ago)
• Default Branch: main
• Last Pushed: 2021-09-28T15:54:57.000Z (about 3 years ago)
• Last Synced: 2023-07-27T21:55:01.339Z (over 1 year ago)
• Topics: dns, golang, network, resolver
• Language: Go
• Homepage:
• Size: 20.5 KB
• Stars: 4
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# mem-resolver

memresolver is an in-memory golang resolver that allows to override current golang Lookup func literals

## How to use it

Create your custom Lookup function, is it common to overwrite LookupIP, that is the one used by the Dialer so we can redirect custom domains, per example.

```go

func myLookupIP(ctx context.Context, network, host string) ([]net.IP, error) {

	// fqdn appends a dot

	if "mycustom.mydomain" == strings.TrimSuffix(host, ".") {

		return []net.IP{net.ParseIP("127.0.0.1")}, nil

	}

	return net.DefaultResolver.LookupIP(ctx, network, host)

}

```

Once we have our cusotm Lookup function we create a custom `net.Resolver` 

```go

	f := &MemResolver{

		LookupIP: myLookupIP,

	}

	// override lookupIP

	resolver := NewMemoryResolver(f)

```

This custom resolver implements a `Dial` function that can be used to override the `net.Dialer` resolver.

```go

	tr := &http.Transport{

		Proxy: http.ProxyFromEnvironment,

		DialContext: (&net.Dialer{

			Timeout:   30 * time.Second,

			KeepAlive: 30 * time.Second,

			Resolver:  resolver,

		}).DialContext,

	}

	client := &http.Client{

		Transport: tr,

	}

```

Check [example_test.go](./example_test.go) for a full example.