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package forward
import (
"sync/atomic"
"github.com/miekg/dns"
)
// For HC we send to . IN NS +norec message to the upstream. Dial timeouts and empty
// replies are considered fails, basically anything else constitutes a healthy upstream.
// Check is used as the up.Func in the up.Probe.
func (p *Proxy) Check() error {
err := p.send()
if err != nil {
HealthcheckFailureCount.WithLabelValues(p.addr).Add(1)
atomic.AddUint32(&p.fails, 1)
return err
}
atomic.StoreUint32(&p.fails, 0)
return nil
}
func (p *Proxy) send() error {
hcping := new(dns.Msg)
hcping.SetQuestion(".", dns.TypeNS)
hcping.RecursionDesired = false
m, _, err := p.client.Exchange(hcping, p.addr)
// If we got a header, we're alright, basically only care about I/O errors 'n stuff
if err != nil && m != nil {
// Silly check, something sane came back
if m.Response || m.Opcode == dns.OpcodeQuery {
err = nil
}
}
return err
}
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