AdGuardHome/internal/aghnet/systemresolvers.go

79 lines
2.2 KiB
Go

package aghnet
import (
"time"
"github.com/AdguardTeam/AdGuardHome/internal/agherr"
"github.com/AdguardTeam/golibs/log"
)
// DefaultRefreshIvl is the default period of time between refreshing cached
// addresses.
// const DefaultRefreshIvl = 5 * time.Minute
// HostGenFunc is the signature for functions generating fake hostnames. The
// implementation must be safe for concurrent use.
type HostGenFunc func() (host string)
// unit is an alias for an existing map value.
type unit = struct{}
// SystemResolvers helps to work with local resolvers' addresses provided by OS.
type SystemResolvers interface {
// Get returns the slice of local resolvers' addresses.
// It should be safe for concurrent use.
Get() (rs []string)
// refresh refreshes the local resolvers' addresses cache. It should be
// safe for concurrent use.
refresh() (err error)
}
const (
// fakeDialErr is an error which dialFunc is expected to return.
fakeDialErr agherr.Error = "this error signals the successful dialFunc work"
// badAddrPassedErr is returned when dialFunc can't parse an IP address.
badAddrPassedErr agherr.Error = "the passed string is not a valid IP address"
)
// refreshWithTicker refreshes the cache of sr after each tick form tickCh.
func refreshWithTicker(sr SystemResolvers, tickCh <-chan time.Time) {
defer agherr.LogPanic("systemResolvers")
// TODO(e.burkov): Implement a functionality to stop ticker.
for range tickCh {
err := sr.refresh()
if err != nil {
log.Error("systemResolvers: error in refreshing goroutine: %s", err)
continue
}
log.Debug("systemResolvers: local addresses cache is refreshed")
}
}
// NewSystemResolvers returns a SystemResolvers with the cache refresh rate
// defined by refreshIvl. It disables auto-resfreshing if refreshIvl is 0. If
// nil is passed for hostGenFunc, the default generator will be used.
func NewSystemResolvers(
refreshIvl time.Duration,
hostGenFunc HostGenFunc,
) (sr SystemResolvers, err error) {
sr = newSystemResolvers(refreshIvl, hostGenFunc)
// Fill cache.
err = sr.refresh()
if err != nil {
return nil, err
}
if refreshIvl > 0 {
ticker := time.NewTicker(refreshIvl)
go refreshWithTicker(sr, ticker.C)
}
return sr, nil
}