package aghnet import ( "time" "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) // 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) } // refreshWithTicker refreshes the cache of sr after each tick form tickCh. func refreshWithTicker(sr SystemResolvers, tickCh <-chan time.Time) { defer log.OnPanic("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 }