40 lines
883 B
Go
40 lines
883 B
Go
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package dns
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import (
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"context"
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"errors"
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"fmt"
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"net"
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)
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// Client is a simple plaintext UDP DNS client, to be used for healthchecks.
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// Note the client connects to a DNS server only over UDP on port 53,
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// because we don't want to use DoT or DoH and impact the TCP connections
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// when running a healthcheck.
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type Client struct{}
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func New() *Client {
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return &Client{}
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}
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var ErrLookupNoIPs = errors.New("no IPs found from DNS lookup")
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func (c *Client) Check(ctx context.Context) error {
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resolver := &net.Resolver{
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PreferGo: true,
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Dial: func(ctx context.Context, _, _ string) (net.Conn, error) {
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dialer := net.Dialer{}
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return dialer.DialContext(ctx, "udp", "1.1.1.1:53")
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},
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}
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ips, err := resolver.LookupIP(ctx, "ip", "github.com")
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switch {
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case err != nil:
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return err
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case len(ips) == 0:
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return fmt.Errorf("%w", ErrLookupNoIPs)
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default:
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return nil
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}
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}
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