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https://github.com/coredns/coredns.git
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c349446a23
Create plugin/pkg/transport that holds the transport related functions. This needed to be a new pkg to prevent cyclic import errors. This cleans up a bunch of duplicated code in core/dnsserver that also tried to parse a transport (now all done in transport.Parse). Signed-off-by: Miek Gieben <miek@miek.nl>
90 lines
2.4 KiB
Go
90 lines
2.4 KiB
Go
// Package forward implements a forwarding proxy. It caches an upstream net.Conn for some time, so if the same
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// client returns the upstream's Conn will be precached. Depending on how you benchmark this looks to be
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// 50% faster than just opening a new connection for every client. It works with UDP and TCP and uses
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// inband healthchecking.
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package forward
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import (
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"context"
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"github.com/coredns/coredns/plugin/pkg/transport"
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"github.com/coredns/coredns/request"
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"github.com/miekg/dns"
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)
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// Forward forward the request in state as-is. Unlike Lookup that adds EDNS0 suffix to the message.
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// Forward may be called with a nil f, an error is returned in that case.
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func (f *Forward) Forward(state request.Request) (*dns.Msg, error) {
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if f == nil {
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return nil, ErrNoForward
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}
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fails := 0
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var upstreamErr error
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for _, proxy := range f.List() {
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if proxy.Down(f.maxfails) {
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fails++
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if fails < len(f.proxies) {
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continue
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}
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// All upstream proxies are dead, assume healtcheck is complete broken and randomly
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// select an upstream to connect to.
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proxy = f.List()[0]
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}
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ret, err := proxy.Connect(context.Background(), state, f.opts)
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ret, err = truncated(state, ret, err)
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upstreamErr = err
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if err != nil {
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if fails < len(f.proxies) {
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continue
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}
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break
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}
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// Check if the reply is correct; if not return FormErr.
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if !state.Match(ret) {
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return state.ErrorMessage(dns.RcodeFormatError), nil
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}
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return ret, err
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}
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if upstreamErr != nil {
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return nil, upstreamErr
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}
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return nil, ErrNoHealthy
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}
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// Lookup will use name and type to forge a new message and will send that upstream. It will
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// set any EDNS0 options correctly so that downstream will be able to process the reply.
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// Lookup may be called with a nil f, an error is returned in that case.
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func (f *Forward) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
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if f == nil {
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return nil, ErrNoForward
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}
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req := new(dns.Msg)
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req.SetQuestion(name, typ)
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state.SizeAndDo(req)
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state2 := request.Request{W: state.W, Req: req}
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return f.Forward(state2)
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}
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// NewLookup returns a Forward that can be used for plugin that need an upstream to resolve external names.
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// Note that the caller must run Close on the forward to stop the health checking goroutines.
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func NewLookup(addr []string) *Forward {
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f := New()
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for i := range addr {
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p := NewProxy(addr[i], transport.DNS)
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f.SetProxy(p)
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}
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return f
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}
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