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ft: LookupSRV function to work with CNAME records #5710

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ft: LookupSRV function to work with CNAME records #5710

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ad16c5d
feat: cname handling in lookupsrv
Atharva-Shinde Sep 21, 2022
644683f
feat: cname handling in lookupsrv
Atharva-Shinde Sep 21, 2022
a1f40a7
Merge branch 'main' into feature-cname-dnssrv-resolution
Atharva-Shinde Sep 22, 2022
756cb3e
Merge branch 'main' into feature-cname-dnssrv-resolution
Atharva-Shinde Sep 23, 2022
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22 changes: 19 additions & 3 deletions pkg/discovery/dns/miekgdns/resolver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,16 @@ type Resolver struct {
ResolvConf string
}

func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error) {
func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (cname string, resp []*net.SRV, err error) {
return r.lookupSRV(service, proto, name, 1, 8)
}

func (r *Resolver) lookupSRV(service, proto, name string, currIteration, maxIterations int) (cname string, resp []*net.SRV, err error) {
// We want to protect from infinite loops when resolving DNS records recursively.
if currIteration > maxIterations {
return "", nil, errors.Errorf("maximum number of recursive iterations reached (%d)", maxIterations)
}

var target string
if service == "" && proto == "" {
target = name
Expand All @@ -35,18 +44,25 @@ func (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (
for _, record := range response.Answer {
switch addr := record.(type) {
case *dns.SRV:
addrs = append(addrs, &net.SRV{
resp = append(resp, &net.SRV{
Weight: addr.Weight,
Target: addr.Target,
Priority: addr.Priority,
Port: addr.Port,
})
case *dns.CNAME:
// Recursively resolve it.
_, addrs, err := r.lookupSRV(service, proto, target, currIteration+1, maxIterations)
if err != nil {
return "", nil, errors.Wrapf(err, "recursively resolve %s", addr.Target)
}
resp = append(resp, addrs...)
default:
return "", nil, errors.Errorf("invalid SRV response record %s", record)
}
}

return "", addrs, nil
return "", resp, nil
}

func (r *Resolver) LookupIPAddr(_ context.Context, host string) ([]net.IPAddr, error) {
Expand Down