forked from coredns/coredns
/
connect.go
137 lines (115 loc) · 3.54 KB
/
connect.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
// Package forward implements a forwarding proxy. It caches an upstream net.Conn for some time, so if the same
// client returns the upstream's Conn will be precached. Depending on how you benchmark this looks to be
// 50% faster than just opening a new connection for every client. It works with UDP and TCP and uses
// inband healthchecking.
package forward
import (
"context"
"io"
"strconv"
"sync/atomic"
"time"
"github.com/coredns/coredns/request"
"github.com/miekg/dns"
)
// limitTimeout is a utility function to auto-tune timeout values
// average observed time is moved towards the last observed delay moderated by a weight
// next timeout to use will be the double of the computed average, limited by min and max frame.
func limitTimeout(currentAvg *int64, minValue time.Duration, maxValue time.Duration) time.Duration {
rt := time.Duration(atomic.LoadInt64(currentAvg))
if rt < minValue {
return minValue
}
if rt < maxValue/2 {
return 2 * rt
}
return maxValue
}
func averageTimeout(currentAvg *int64, observedDuration time.Duration, weight int64) {
dt := time.Duration(atomic.LoadInt64(currentAvg))
atomic.AddInt64(currentAvg, int64(observedDuration-dt)/weight)
}
func (t *Transport) dialTimeout() time.Duration {
return limitTimeout(&t.avgDialTime, minDialTimeout, maxDialTimeout)
}
func (t *Transport) updateDialTimeout(newDialTime time.Duration) {
averageTimeout(&t.avgDialTime, newDialTime, cumulativeAvgWeight)
}
// Dial dials the address configured in transport, potentially reusing a connection or creating a new one.
func (t *Transport) Dial(proto string) (*dns.Conn, bool, error) {
// If tls has been configured; use it.
if t.tlsConfig != nil {
proto = "tcp-tls"
}
t.dial <- proto
c := <-t.ret
if c != nil {
return c, true, nil
}
reqTime := time.Now()
timeout := t.dialTimeout()
if proto == "tcp-tls" {
conn, err := dns.DialTimeoutWithTLS("tcp", t.addr, t.tlsConfig, timeout)
t.updateDialTimeout(time.Since(reqTime))
return conn, false, err
}
conn, err := dns.DialTimeout(proto, t.addr, timeout)
t.updateDialTimeout(time.Since(reqTime))
return conn, false, err
}
// Connect selects an upstream, sends the request and waits for a response.
func (p *Proxy) Connect(ctx context.Context, state request.Request, opts options) (*dns.Msg, error) {
start := time.Now()
proto := ""
switch {
case opts.forceTCP: // TCP flag has precedence over UDP flag
proto = "tcp"
case opts.preferUDP:
proto = "udp"
default:
proto = state.Proto()
}
conn, cached, err := p.transport.Dial(proto)
if err != nil {
return nil, err
}
// Set buffer size correctly for this client.
conn.UDPSize = uint16(state.Size())
if conn.UDPSize < 512 {
conn.UDPSize = 512
}
conn.SetWriteDeadline(time.Now().Add(maxTimeout))
if err := conn.WriteMsg(state.Req); err != nil {
conn.Close() // not giving it back
if err == io.EOF && cached {
return nil, ErrCachedClosed
}
return nil, err
}
var ret *dns.Msg
conn.SetReadDeadline(time.Now().Add(readTimeout))
for {
ret, err = conn.ReadMsg()
if err != nil {
conn.Close() // not giving it back
if err == io.EOF && cached {
return nil, ErrCachedClosed
}
return ret, err
}
// drop out-of-order responses
if state.Req.Id == ret.Id {
break
}
}
p.transport.Yield(conn)
rc, ok := dns.RcodeToString[ret.Rcode]
if !ok {
rc = strconv.Itoa(ret.Rcode)
}
RequestCount.WithLabelValues(p.addr).Add(1)
RcodeCount.WithLabelValues(rc, p.addr).Add(1)
RequestDuration.WithLabelValues(p.addr).Observe(time.Since(start).Seconds())
return ret, nil
}
const cumulativeAvgWeight = 4