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router.go
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router.go
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package rdns
import (
"errors"
"expvar"
"fmt"
"github.com/miekg/dns"
"github.com/sirupsen/logrus"
)
// Router for DNS requests based on query type and/or name. Implements the Resolver interface.
type Router struct {
id string
routes []*route
metrics *RouterMetrics
}
var _ Resolver = &Router{}
type RouterMetrics struct {
// Next route counts.
route *expvar.Map
// Next route failure counts.
failure *expvar.Map
// Count of available routes.
available *expvar.Int
}
func NewRouterMetrics(id string, available int) *RouterMetrics {
avail := getVarInt("router", id, "available")
avail.Set(int64(available))
return &RouterMetrics{
route: getVarMap("router", id, "route"),
failure: getVarMap("router", id, "failure"),
available: avail,
}
}
// NewRouter returns a new router instance. The router won't have any routes and can only be used
// once Add() is called to setup a route.
func NewRouter(id string) *Router {
return &Router{
id: id,
metrics: NewRouterMetrics(id, 0),
}
}
// Resolve a request by routing it to the right resolved based on the routes setup in the router.
func (r *Router) Resolve(q *dns.Msg, ci ClientInfo) (*dns.Msg, error) {
if len(q.Question) < 1 {
return nil, errors.New("no question in query")
}
question := q.Question[0]
log := logger(r.id, q, ci)
for _, route := range r.routes {
if !route.match(q, ci) {
continue
}
log.WithFields(logrus.Fields{
"route": route.String(),
"resolver": route.resolver.String()},
).Debug("routing query to resolver")
r.metrics.route.Add(route.resolver.String(), 1)
a, err := route.resolver.Resolve(q, ci)
if err != nil {
r.metrics.failure.Add(route.resolver.String(), 1)
}
return a, err
}
return nil, fmt.Errorf("no route for %s", question.String())
}
// Add a new route to the router. New routes are appended to the existing
// ones and are evaluated in the same order they're added. The default
// route (no name, no type) should be added last since subsequently added
// routes won't have any impact. Name is a regular expression that is
// applied to the name in the first question section of the DNS message.
// Source is an IP or network in CIDR format.
func (r *Router) Add(routes ...*route) {
r.routes = append(r.routes, routes...)
r.metrics.available.Add(1)
}
func (r *Router) String() string {
return r.id
}