96 lines
2.2 KiB
Go
96 lines
2.2 KiB
Go
package forward
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import (
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"crypto/tls"
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"sync/atomic"
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"time"
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"github.com/coredns/coredns/plugin/pkg/transport"
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"github.com/miekg/dns"
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)
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// HealthChecker checks the upstream health.
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type HealthChecker interface {
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Check(*Proxy) error
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SetTLSConfig(*tls.Config)
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SetRecursionDesired(bool)
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GetRecursionDesired() bool
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SetTCPTransport()
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}
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// dnsHc is a health checker for a DNS endpoint (DNS, and DoT).
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type dnsHc struct {
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c *dns.Client
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recursionDesired bool
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}
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var (
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hcReadTimeout = 1 * time.Second
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hcWriteTimeout = 1 * time.Second
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)
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// NewHealthChecker returns a new HealthChecker based on transport.
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func NewHealthChecker(trans string, recursionDesired bool) HealthChecker {
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switch trans {
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case transport.DNS, transport.TLS:
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c := new(dns.Client)
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c.Net = "udp"
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c.ReadTimeout = hcReadTimeout
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c.WriteTimeout = hcWriteTimeout
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return &dnsHc{c: c, recursionDesired: recursionDesired}
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}
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log.Warningf("No healthchecker for transport %q", trans)
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return nil
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}
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func (h *dnsHc) SetTLSConfig(cfg *tls.Config) {
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h.c.Net = "tcp-tls"
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h.c.TLSConfig = cfg
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}
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func (h *dnsHc) SetRecursionDesired(recursionDesired bool) {
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h.recursionDesired = recursionDesired
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}
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func (h *dnsHc) GetRecursionDesired() bool {
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return h.recursionDesired
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}
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func (h *dnsHc) SetTCPTransport() {
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h.c.Net = "tcp"
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}
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// For HC we send to . IN NS +[no]rec message to the upstream. Dial timeouts and empty
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// replies are considered fails, basically anything else constitutes a healthy upstream.
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// Check is used as the up.Func in the up.Probe.
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func (h *dnsHc) Check(p *Proxy) error {
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err := h.send(p.addr)
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if err != nil {
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HealthcheckFailureCount.WithLabelValues(p.addr).Add(1)
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atomic.AddUint32(&p.fails, 1)
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return err
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}
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atomic.StoreUint32(&p.fails, 0)
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return nil
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}
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func (h *dnsHc) send(addr string) error {
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ping := new(dns.Msg)
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ping.SetQuestion(".", dns.TypeNS)
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ping.MsgHdr.RecursionDesired = h.recursionDesired
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m, _, err := h.c.Exchange(ping, addr)
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// If we got a header, we're alright, basically only care about I/O errors 'n stuff.
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if err != nil && m != nil {
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// Silly check, something sane came back.
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if m.Response || m.Opcode == dns.OpcodeQuery {
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err = nil
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}
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}
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return err
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}
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