0af9b9b16f
As plugin/proxy always returns compressed messages, it's important to set this before calling Scrub(), as some messages will be unnecessarily truncated otherwise.
108 lines
2.4 KiB
Go
108 lines
2.4 KiB
Go
package proxy
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import (
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"net"
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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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"golang.org/x/net/context"
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)
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type dnsEx struct {
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Timeout time.Duration
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Options
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}
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// Options define the options understood by dns.Exchange.
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type Options struct {
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ForceTCP bool // If true use TCP for upstream no matter what
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}
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func newDNSEx() *dnsEx {
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return newDNSExWithOption(Options{})
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}
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func newDNSExWithOption(opt Options) *dnsEx {
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return &dnsEx{Timeout: defaultTimeout * time.Second, Options: opt}
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}
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func (d *dnsEx) Transport() string {
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if d.Options.ForceTCP {
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return "tcp"
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}
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// The protocol will be determined by `state.Proto()` during Exchange.
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return ""
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}
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func (d *dnsEx) Protocol() string { return "dns" }
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func (d *dnsEx) OnShutdown(p *Proxy) error { return nil }
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func (d *dnsEx) OnStartup(p *Proxy) error { return nil }
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// Exchange implements the Exchanger interface.
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func (d *dnsEx) Exchange(ctx context.Context, addr string, state request.Request) (*dns.Msg, error) {
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proto := state.Proto()
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if d.Options.ForceTCP {
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proto = "tcp"
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}
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co, err := net.DialTimeout(proto, addr, d.Timeout)
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if err != nil {
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return nil, err
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}
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reply, _, err := d.ExchangeConn(state.Req, co)
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co.Close()
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if reply != nil && reply.Truncated {
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// Suppress proxy error for truncated responses
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err = nil
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}
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if err != nil {
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return nil, err
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}
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reply.Compress = true
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reply.Id = state.Req.Id
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// When using force_tcp the upstream can send a message that is too big for
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// the udp buffer, hence we need to truncate the message to at least make it
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// fit the udp buffer.
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reply, _ = state.Scrub(reply)
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return reply, nil
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}
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func (d *dnsEx) ExchangeConn(m *dns.Msg, co net.Conn) (*dns.Msg, time.Duration, error) {
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start := time.Now()
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r, err := exchange(m, co)
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rtt := time.Since(start)
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return r, rtt, err
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}
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func exchange(m *dns.Msg, co net.Conn) (*dns.Msg, error) {
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opt := m.IsEdns0()
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udpsize := uint16(dns.MinMsgSize)
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// If EDNS0 is used use that for size.
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if opt != nil && opt.UDPSize() >= dns.MinMsgSize {
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udpsize = opt.UDPSize()
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}
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dnsco := &dns.Conn{Conn: co, UDPSize: udpsize}
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writeDeadline := time.Now().Add(defaultTimeout)
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dnsco.SetWriteDeadline(writeDeadline)
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dnsco.WriteMsg(m)
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readDeadline := time.Now().Add(defaultTimeout)
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co.SetReadDeadline(readDeadline)
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r, err := dnsco.ReadMsg()
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dnsco.Close()
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if r == nil {
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return nil, err
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}
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return r, err
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}
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