AdGuardHome/internal/aghnet/systemresolvers_others.go

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// +build !windows
package aghnet
import (
"context"
"errors"
"fmt"
"net"
"sync"
"time"
"github.com/AdguardTeam/AdGuardHome/internal/agherr"
)
// defaultHostGen is the default method of generating host for Refresh.
func defaultHostGen() (host string) {
// TODO(e.burkov): Use strings.Builder.
return fmt.Sprintf("test%d.org", time.Now().UnixNano())
}
// systemResolvers is a default implementation of SystemResolvers interface.
type systemResolvers struct {
resolver *net.Resolver
hostGenFunc HostGenFunc
// addrs is the map that contains cached local resolvers' addresses.
addrs map[string]unit
addrsLock sync.RWMutex
}
func (sr *systemResolvers) Refresh() (err error) {
defer agherr.Annotate("systemResolvers: %w", &err)
_, err = sr.resolver.LookupHost(context.Background(), sr.hostGenFunc())
dnserr := &net.DNSError{}
if errors.As(err, &dnserr) && dnserr.Err == fakeDialErr.Error() {
return nil
}
return err
}
func newSystemResolvers(refreshIvl time.Duration, hostGenFunc HostGenFunc) (sr SystemResolvers) {
if hostGenFunc == nil {
hostGenFunc = defaultHostGen
}
s := &systemResolvers{
resolver: &net.Resolver{
PreferGo: true,
},
hostGenFunc: hostGenFunc,
addrs: make(map[string]unit),
}
s.resolver.Dial = s.dialFunc
return s
}
// dialFunc gets the resolver's address and puts it into internal cache.
func (sr *systemResolvers) dialFunc(_ context.Context, _, address string) (_ net.Conn, err error) {
// Just validate the passed address is a valid IP.
var host string
host, err = SplitHost(address)
if err != nil {
// TODO(e.burkov): Maybe use a structured badAddrPassedErr to
// allow unwrapping of the real error.
return nil, fmt.Errorf("%s: %w", err, badAddrPassedErr)
}
if net.ParseIP(host) == nil {
return nil, fmt.Errorf("parsing %q: %w", host, badAddrPassedErr)
}
sr.addrsLock.Lock()
defer sr.addrsLock.Unlock()
sr.addrs[address] = unit{}
return nil, fakeDialErr
}
func (sr *systemResolvers) Get() (rs []string) {
sr.addrsLock.RLock()
defer sr.addrsLock.RUnlock()
addrs := sr.addrs
rs = make([]string, len(addrs))
var i int
for addr := range addrs {
rs[i] = addr
i++
}
return rs
}