80 lines
2.1 KiB
Go
80 lines
2.1 KiB
Go
package aghnet
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import (
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"time"
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"github.com/AdguardTeam/AdGuardHome/internal/agherr"
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"github.com/AdguardTeam/dnsproxy/upstream"
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"github.com/miekg/dns"
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)
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// This package is not the best place for this functionality, but we put it here
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// since we need to use it in both rDNS (home) and dnsServer (dnsforward).
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// NoUpstreamsErr should be returned when there are no upstreams inside
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// Exchanger implementation.
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const NoUpstreamsErr agherr.Error = "no upstreams specified"
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// Exchanger represents an object able to resolve DNS messages.
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//
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// TODO(e.burkov): Maybe expand with method like ExchangeParallel to be able to
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// use user's upstream mode settings. Also, think about Update method to
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// refresh the internal state.
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type Exchanger interface {
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Exchange(req *dns.Msg) (resp *dns.Msg, err error)
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}
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// multiAddrExchanger is the default implementation of Exchanger interface.
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type multiAddrExchanger struct {
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ups []upstream.Upstream
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}
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// NewMultiAddrExchanger creates an Exchanger instance from passed addresses.
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// It returns an error if any of addrs failed to become an upstream.
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func NewMultiAddrExchanger(addrs []string, timeout time.Duration) (e Exchanger, err error) {
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defer agherr.Annotate("exchanger: %w", &err)
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if len(addrs) == 0 {
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return &multiAddrExchanger{}, nil
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}
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var ups []upstream.Upstream = make([]upstream.Upstream, 0, len(addrs))
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for _, addr := range addrs {
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var u upstream.Upstream
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u, err = upstream.AddressToUpstream(addr, upstream.Options{Timeout: timeout})
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if err != nil {
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return nil, err
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}
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ups = append(ups, u)
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}
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return &multiAddrExchanger{ups: ups}, nil
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}
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// Exсhange performs a query to each resolver until first response.
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func (e *multiAddrExchanger) Exchange(req *dns.Msg) (resp *dns.Msg, err error) {
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defer agherr.Annotate("exchanger: %w", &err)
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// TODO(e.burkov): Maybe prohibit the initialization without upstreams.
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if len(e.ups) == 0 {
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return nil, NoUpstreamsErr
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}
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var errs []error
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for _, u := range e.ups {
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resp, err = u.Exchange(req)
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if err != nil {
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errs = append(errs, err)
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continue
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}
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if resp != nil {
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return resp, nil
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}
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}
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return nil, agherr.Many("can't exchange", errs...)
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}
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