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bundled_upstream.go
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/
bundled_upstream.go
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/*
* Copyright (C) 2020-2022, IrineSistiana
*
* This file is part of mosdns.
*
* mosdns is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* mosdns is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
package bundled_upstream
import (
"context"
"errors"
"github.com/IrineSistiana/mosdns/v4/pkg/query_context"
"github.com/miekg/dns"
"go.uber.org/zap"
)
type Upstream interface {
Exchange(ctx context.Context, q *dns.Msg) (*dns.Msg, error)
Address() string
Trusted() bool
}
type BundledUpstream struct {
us []Upstream
logger *zap.Logger
}
// NewBundledUpstream creates a BundledUpstream.
// us must contain at least one Upstream.
// To disable logger, set it to nil.
func NewBundledUpstream(us []Upstream, logger *zap.Logger) *BundledUpstream {
if len(us) < 1 {
panic("us must contain at least one Upstream")
}
if logger == nil {
logger = zap.NewNop()
}
return &BundledUpstream{us: us, logger: logger}
}
type parallelResult struct {
r *dns.Msg
err error
from Upstream
}
func (bu *BundledUpstream) ExchangeParallel(ctx context.Context, qCtx *query_context.Context) (*dns.Msg, error) {
q := qCtx.Q()
t := len(bu.us)
if t == 1 {
u := bu.us[0]
r, err := u.Exchange(ctx, q)
if err != nil {
return nil, err
}
bu.logger.Debug("response received", qCtx.InfoField(), zap.String("from", u.Address()))
return r, nil
}
c := make(chan *parallelResult, t) // use buf chan to avoid blocking.
qCopy := q.Copy() // qCtx is not safe for concurrent use.
for _, u := range bu.us {
u := u
go func() {
r, err := u.Exchange(ctx, qCopy)
c <- ¶llelResult{
r: r,
err: err,
from: u,
}
}()
}
var candidateErrReply *parallelResult
for i := 0; i < t; i++ {
select {
case res := <-c:
if res.err != nil {
bu.logger.Warn("upstream failed", qCtx.InfoField(), zap.String("from", res.from.Address()), zap.Error(res.err))
continue
}
if res.r.Rcode == dns.RcodeSuccess || res.from.Trusted() {
bu.logger.Debug("response accepted", qCtx.InfoField(), zap.String("from", res.from.Address()))
return res.r, nil
}
if candidateErrReply == nil {
candidateErrReply = res
}
bu.logger.Debug("untrusted upstream returned an err rcode", qCtx.InfoField(), zap.String("from", res.from.Address()), zap.Int("rcode", res.r.Rcode))
case <-ctx.Done():
return nil, ctx.Err()
}
}
// all upstreams failed or returned an error rcode.
if candidateErrReply != nil {
bu.logger.Debug("candidate error response accepted", qCtx.InfoField(), zap.String("from", candidateErrReply.from.Address()))
return candidateErrReply.r, nil
}
return nil, errors.New("no response")
}