aa7744dc86
Go vet and golint the new code once again. Drop Name from NameTemplate - it's cleaner: nametemplate.Template.
97 lines
2 KiB
Go
97 lines
2 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/miekg/coredns/middleware/pkg/singleflight"
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"github.com/miekg/coredns/request"
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"github.com/miekg/dns"
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)
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type client struct {
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Timeout time.Duration
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group *singleflight.Group
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}
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func newClient() *client {
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return &client{Timeout: defaultTimeout, group: new(singleflight.Group)}
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}
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// ServeDNS does not satisfy middleware.Handler, instead it interacts with the upstream
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// and returns the respons or an error.
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func (c *client) ServeDNS(w dns.ResponseWriter, r *dns.Msg, u *UpstreamHost) (*dns.Msg, error) {
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co, err := net.DialTimeout(request.Proto(w), u.Name, c.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 := c.Exchange(r, 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 = r.Id
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return reply, nil
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}
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func (c *client) Exchange(m *dns.Msg, co net.Conn) (*dns.Msg, time.Duration, error) {
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t := "nop"
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if t1, ok := dns.TypeToString[m.Question[0].Qtype]; ok {
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t = t1
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}
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cl := "nop"
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if cl1, ok := dns.ClassToString[m.Question[0].Qclass]; ok {
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cl = cl1
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}
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start := time.Now()
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// Name needs to be normalized! Bug in go dns.
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r, err := c.group.Do(m.Question[0].Name+t+cl, func() (interface{}, error) {
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ret, e := c.exchange(m, co)
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return ret, e
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})
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rtt := time.Since(start)
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if err != nil {
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return &dns.Msg{}, rtt, err
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}
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r1 := r.(dns.Msg)
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return &r1, rtt, nil
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}
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// exchange does *not* return a pointer to dns.Msg because that leads to buffer reuse when
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// group.Do is used in Exchange.
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func (c *client) 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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dnsco.WriteMsg(m)
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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 dns.Msg{}, err
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}
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return *r, err
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}
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