package aghnet import ( "fmt" "io" "io/fs" "net/netip" "path" "sync/atomic" "github.com/AdguardTeam/AdGuardHome/internal/aghos" "github.com/AdguardTeam/golibs/errors" "github.com/AdguardTeam/golibs/hostsfile" "github.com/AdguardTeam/golibs/log" ) // hostsContainerPrefix is a prefix for logging and wrapping errors in // HostsContainer's methods. const hostsContainerPrefix = "hosts container" // HostsContainer stores the relevant hosts database provided by the OS and // processes both A/AAAA and PTR DNS requests for those. type HostsContainer struct { // done is the channel to sign closing the container. done chan struct{} // updates is the channel for receiving updated hosts. updates chan *hostsfile.DefaultStorage // current is the last set of hosts parsed. current atomic.Pointer[hostsfile.DefaultStorage] // fsys is the working file system to read hosts files from. fsys fs.FS // watcher tracks the changes in specified files and directories. watcher aghos.FSWatcher // patterns stores specified paths in the fs.Glob-compatible form. patterns []string } // ErrNoHostsPaths is returned when there are no valid paths to watch passed to // the HostsContainer. const ErrNoHostsPaths errors.Error = "no valid paths to hosts files provided" // NewHostsContainer creates a container of hosts, that watches the paths with // w. listID is used as an identifier of the underlying rules list. paths // shouldn't be empty and each of paths should locate either a file or a // directory in fsys. fsys and w must be non-nil. func NewHostsContainer( fsys fs.FS, w aghos.FSWatcher, paths ...string, ) (hc *HostsContainer, err error) { defer func() { err = errors.Annotate(err, "%s: %w", hostsContainerPrefix) }() if len(paths) == 0 { return nil, ErrNoHostsPaths } var patterns []string patterns, err = pathsToPatterns(fsys, paths) if err != nil { return nil, err } else if len(patterns) == 0 { return nil, ErrNoHostsPaths } hc = &HostsContainer{ done: make(chan struct{}, 1), updates: make(chan *hostsfile.DefaultStorage, 1), fsys: fsys, watcher: w, patterns: patterns, } log.Debug("%s: starting", hostsContainerPrefix) // Load initially. if err = hc.refresh(); err != nil { return nil, err } for _, p := range paths { if err = w.Add(p); err != nil { if !errors.Is(err, fs.ErrNotExist) { return nil, fmt.Errorf("adding path: %w", err) } log.Debug("%s: %s is expected to exist but doesn't", hostsContainerPrefix, p) } } go hc.handleEvents() return hc, nil } // Close implements the [io.Closer] interface for *HostsContainer. It closes // both itself and its [aghos.FSWatcher]. Close must only be called once. func (hc *HostsContainer) Close() (err error) { log.Debug("%s: closing", hostsContainerPrefix) err = errors.Annotate(hc.watcher.Close(), "closing fs watcher: %w") // Go on and close the container either way. close(hc.done) return err } // Upd returns the channel into which the updates are sent. The updates // themselves must not be modified. func (hc *HostsContainer) Upd() (updates <-chan *hostsfile.DefaultStorage) { return hc.updates } // type check var _ hostsfile.Storage = (*HostsContainer)(nil) // ByAddr implements the [hostsfile.Storage] interface for *HostsContainer. func (hc *HostsContainer) ByAddr(addr netip.Addr) (names []string) { return hc.current.Load().ByAddr(addr) } // ByName implements the [hostsfile.Storage] interface for *HostsContainer. func (hc *HostsContainer) ByName(name string) (addrs []netip.Addr) { return hc.current.Load().ByName(name) } // pathsToPatterns converts paths into patterns compatible with fs.Glob. func pathsToPatterns(fsys fs.FS, paths []string) (patterns []string, err error) { for i, p := range paths { var fi fs.FileInfo fi, err = fs.Stat(fsys, p) if err != nil { if errors.Is(err, fs.ErrNotExist) { continue } // Don't put a filename here since it's already added by [fs.Stat]. return nil, fmt.Errorf("path at index %d: %w", i, err) } if fi.IsDir() { p = path.Join(p, "*") } patterns = append(patterns, p) } return patterns, nil } // handleEvents concurrently handles the file system events. It closes the // update channel of HostsContainer when finishes. It is intended to be used as // a goroutine. func (hc *HostsContainer) handleEvents() { defer log.OnPanic(fmt.Sprintf("%s: handling events", hostsContainerPrefix)) defer close(hc.updates) eventsCh := hc.watcher.Events() ok := eventsCh != nil for ok { select { case _, ok = <-eventsCh: if !ok { log.Debug("%s: watcher closed the events channel", hostsContainerPrefix) continue } if err := hc.refresh(); err != nil { log.Error("%s: warning: refreshing: %s", hostsContainerPrefix, err) } case _, ok = <-hc.done: // Go on. } } } // sendUpd tries to send the parsed data to the ch. func (hc *HostsContainer) sendUpd(recs *hostsfile.DefaultStorage) { log.Debug("%s: sending upd", hostsContainerPrefix) ch := hc.updates select { case ch <- recs: // Updates are delivered. Go on. case <-ch: ch <- recs log.Debug("%s: replaced the last update", hostsContainerPrefix) case ch <- recs: // The previous update was just read and the next one pushed. Go on. default: log.Error("%s: the updates channel is broken", hostsContainerPrefix) } } // refresh gets the data from specified files and propagates the updates if // needed. // // TODO(e.burkov): Accept a parameter to specify the files to refresh. func (hc *HostsContainer) refresh() (err error) { log.Debug("%s: refreshing", hostsContainerPrefix) // The error is always nil here since no readers passed. strg, _ := hostsfile.NewDefaultStorage() _, err = aghos.FileWalker(func(r io.Reader) (patterns []string, cont bool, err error) { // Don't wrap the error since it's already informative enough as is. return nil, true, hostsfile.Parse(strg, r, nil) }).Walk(hc.fsys, hc.patterns...) if err != nil { // Don't wrap the error since it's informative enough as is. return err } // TODO(e.burkov): Serialize updates using [time.Time]. if !hc.current.Load().Equal(strg) { hc.current.Store(strg) hc.sendUpd(strg) } return nil }