103 lines
2.3 KiB
Go
103 lines
2.3 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 openening 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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"io"
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"strconv"
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"sync/atomic"
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"time"
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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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func (p *Proxy) readTimeout() time.Duration {
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rtt := time.Duration(atomic.LoadInt64(&p.avgRtt))
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if rtt < minTimeout {
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return minTimeout
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}
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if rtt < maxTimeout/2 {
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return 2 * rtt
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}
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return maxTimeout
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}
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func (p *Proxy) updateRtt(newRtt time.Duration) {
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rtt := time.Duration(atomic.LoadInt64(&p.avgRtt))
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atomic.AddInt64(&p.avgRtt, int64((newRtt-rtt)/rttCount))
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}
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func (p *Proxy) connect(ctx context.Context, state request.Request, forceTCP, metric bool) (*dns.Msg, error) {
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atomic.AddInt32(&p.inProgress, 1)
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defer func() {
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if atomic.AddInt32(&p.inProgress, -1) == 0 {
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p.checkStopTransport()
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}
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}()
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if atomic.LoadUint32(&p.state) != running {
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return nil, errStopped
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}
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start := time.Now()
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proto := state.Proto()
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if forceTCP {
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proto = "tcp"
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}
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conn, cached, err := p.Dial(proto)
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if err != nil {
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return nil, err
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}
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// Set buffer size correctly for this client.
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conn.UDPSize = uint16(state.Size())
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if conn.UDPSize < 512 {
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conn.UDPSize = 512
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}
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conn.SetWriteDeadline(time.Now().Add(timeout))
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reqTime := time.Now()
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if err := conn.WriteMsg(state.Req); err != nil {
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conn.Close() // not giving it back
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if err == io.EOF && cached {
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return nil, errCachedClosed
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}
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return nil, err
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}
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conn.SetReadDeadline(time.Now().Add(p.readTimeout()))
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ret, err := conn.ReadMsg()
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if err != nil {
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p.updateRtt(timeout)
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conn.Close() // not giving it back
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if err == io.EOF && cached {
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return nil, errCachedClosed
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}
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return ret, err
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}
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p.updateRtt(time.Since(reqTime))
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p.Yield(conn)
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if metric {
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rc, ok := dns.RcodeToString[ret.Rcode]
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if !ok {
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rc = strconv.Itoa(ret.Rcode)
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}
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RequestCount.WithLabelValues(p.addr).Add(1)
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RcodeCount.WithLabelValues(rc, p.addr).Add(1)
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RequestDuration.WithLabelValues(p.addr).Observe(time.Since(start).Seconds())
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}
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return ret, nil
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}
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const rttCount = 4
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