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// Package upstream abstracts a upstream lookups so that plugins
// can handle them in an unified way.
package upstream
import (
"github.com/miekg/dns"
"github.com/coredns/coredns/core/dnsserver"
"github.com/coredns/coredns/plugin/pkg/nonwriter"
"github.com/coredns/coredns/plugin/pkg/parse"
"github.com/coredns/coredns/plugin/proxy"
"github.com/coredns/coredns/request"
)
// Upstream is used to resolve CNAME targets
type Upstream struct {
self bool
Forward *proxy.Proxy
}
// New creates a new Upstream for given destination(s). If dests is empty it default to upstreaming to
// the coredns process.
func New(dests []string) (Upstream, error) {
u := Upstream{}
if len(dests) == 0 {
u.self = true
return u, nil
}
u.self = false
ups, err := parse.HostPortOrFile(dests...)
if err != nil {
return u, err
}
p := proxy.NewLookup(ups)
u.Forward = &p
return u, nil
}
// Lookup routes lookups to our selves or forward to a remote.
func (u Upstream) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
if u.self {
req := new(dns.Msg)
req.SetQuestion(name, typ)
nw := nonwriter.New(state.W)
server := state.Context.Value(dnsserver.Key{}).(*dnsserver.Server)
server.ServeDNS(state.Context, nw, req)
return nw.Msg, nil
}
if u.Forward != nil {
return u.Forward.Lookup(state, name, typ)
}
return nil, nil
}
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