AdGuardHome/dnsfilter/dnsfilter.go
2019-02-27 15:02:11 +03:00

1042 lines
25 KiB
Go

package dnsfilter
import (
"bufio"
"bytes"
"crypto/sha256"
"encoding/json"
"errors"
"fmt"
"io/ioutil"
"net"
"net/http"
"regexp"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/bluele/gcache"
"github.com/AdguardTeam/golibs/log"
"golang.org/x/net/publicsuffix"
)
const defaultCacheSize = 64 * 1024 // in number of elements
const defaultCacheTime = 30 * time.Minute
const defaultHTTPTimeout = 5 * time.Minute
const defaultHTTPMaxIdleConnections = 100
const defaultSafebrowsingServer = "sb.adtidy.org"
const defaultSafebrowsingURL = "http://%s/safebrowsing-lookup-hash.html?prefixes=%s"
const defaultParentalServer = "pctrl.adguard.com"
const defaultParentalURL = "http://%s/check-parental-control-hash?prefixes=%s&sensitivity=%d"
// ErrInvalidSyntax is returned by AddRule when the rule is invalid
var ErrInvalidSyntax = errors.New("dnsfilter: invalid rule syntax")
// ErrAlreadyExists is returned by AddRule when the rule was already added to the filter
var ErrAlreadyExists = errors.New("dnsfilter: rule was already added")
const shortcutLength = 6 // used for rule search optimization, 6 hits the sweet spot
const enableFastLookup = true // flag for debugging, must be true in production for faster performance
const enableDelayedCompilation = true // flag for debugging, must be true in production for faster performance
// Config allows you to configure DNS filtering with New() or just change variables directly.
type Config struct {
ParentalSensitivity int `yaml:"parental_sensitivity"` // must be either 3, 10, 13 or 17
ParentalEnabled bool `yaml:"parental_enabled"`
SafeSearchEnabled bool `yaml:"safesearch_enabled"`
SafeBrowsingEnabled bool `yaml:"safebrowsing_enabled"`
}
type privateConfig struct {
parentalServer string // access via methods
safeBrowsingServer string // access via methods
}
type rule struct {
text string // text without @@ decorators or $ options
shortcut string // for speeding up lookup
originalText string // original text for reporting back to applications
ip net.IP // IP address (for the case when we're matching a hosts file)
// options
options []string // optional options after $
// parsed options
apps []string
isWhitelist bool
isImportant bool
// user-supplied data
listID int64
// suffix matching
isSuffix bool
suffix string
// compiled regexp
compiled *regexp.Regexp
sync.RWMutex
}
// LookupStats store stats collected during safebrowsing or parental checks
type LookupStats struct {
Requests uint64 // number of HTTP requests that were sent
CacheHits uint64 // number of lookups that didn't need HTTP requests
Pending int64 // number of currently pending HTTP requests
PendingMax int64 // maximum number of pending HTTP requests
}
// Stats store LookupStats for safebrowsing, parental and safesearch
type Stats struct {
Safebrowsing LookupStats
Parental LookupStats
Safesearch LookupStats
}
// Dnsfilter holds added rules and performs hostname matches against the rules
type Dnsfilter struct {
storage map[string]bool // rule storage, not used for matching, just for filtering out duplicates
storageMutex sync.RWMutex
// rules are checked against these lists in the order defined here
important *rulesTable // more important than whitelist and is checked first
whiteList *rulesTable // more important than blacklist
blackList *rulesTable
// HTTP lookups for safebrowsing and parental
client http.Client // handle for http client -- single instance as recommended by docs
transport *http.Transport // handle for http transport used by http client
Config // for direct access by library users, even a = assignment
privateConfig
}
// Filter represents a filter list
type Filter struct {
ID int64 `json:"id"` // auto-assigned when filter is added (see nextFilterID), json by default keeps ID uppercase but we need lowercase
Rules []string `json:"-" yaml:"-"` // not in yaml or json
}
//go:generate stringer -type=Reason
// Reason holds an enum detailing why it was filtered or not filtered
type Reason int
const (
// reasons for not filtering
// NotFilteredNotFound - host was not find in any checks, default value for result
NotFilteredNotFound Reason = iota
// NotFilteredWhiteList - the host is explicitly whitelisted
NotFilteredWhiteList
// NotFilteredError - there was a transitive error during check
NotFilteredError
// reasons for filtering
// FilteredBlackList - the host was matched to be advertising host
FilteredBlackList
// FilteredSafeBrowsing - the host was matched to be malicious/phishing
FilteredSafeBrowsing
// FilteredParental - the host was matched to be outside of parental control settings
FilteredParental
// FilteredInvalid - the request was invalid and was not processed
FilteredInvalid
// FilteredSafeSearch - the host was replaced with safesearch variant
FilteredSafeSearch
)
// these variables need to survive coredns reload
var (
stats Stats
safebrowsingCache gcache.Cache
parentalCache gcache.Cache
safeSearchCache gcache.Cache
)
// Result holds state of hostname check
type Result struct {
IsFiltered bool `json:",omitempty"` // True if the host name is filtered
Reason Reason `json:",omitempty"` // Reason for blocking / unblocking
Rule string `json:",omitempty"` // Original rule text
IP net.IP `json:",omitempty"` // Not nil only in the case of a hosts file syntax
FilterID int64 `json:",omitempty"` // Filter ID the rule belongs to
}
// Matched can be used to see if any match at all was found, no matter filtered or not
func (r Reason) Matched() bool {
return r != NotFilteredNotFound
}
// CheckHost tries to match host against rules, then safebrowsing and parental if they are enabled
func (d *Dnsfilter) CheckHost(host string) (Result, error) {
// sometimes DNS clients will try to resolve ".", which is a request to get root servers
if host == "" {
return Result{Reason: NotFilteredNotFound}, nil
}
host = strings.ToLower(host)
// try filter lists first
result, err := d.matchHost(host)
if err != nil {
return result, err
}
if result.Reason.Matched() {
return result, nil
}
// check safeSearch if no match
if d.SafeSearchEnabled {
result, err = d.checkSafeSearch(host)
if err != nil {
log.Printf("Failed to safesearch HTTP lookup, ignoring check: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
// check safebrowsing if no match
if d.SafeBrowsingEnabled {
result, err = d.checkSafeBrowsing(host)
if err != nil {
// failed to do HTTP lookup -- treat it as if we got empty response, but don't save cache
log.Printf("Failed to do safebrowsing HTTP lookup, ignoring check: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
// check parental if no match
if d.ParentalEnabled {
result, err = d.checkParental(host)
if err != nil {
// failed to do HTTP lookup -- treat it as if we got empty response, but don't save cache
log.Printf("Failed to do parental HTTP lookup, ignoring check: %v", err)
return Result{}, nil
}
if result.Reason.Matched() {
return result, nil
}
}
// nothing matched, return nothing
return Result{}, nil
}
//
// rules table
//
type rulesTable struct {
rulesByHost map[string]*rule
rulesByShortcut map[string][]*rule
rulesLeftovers []*rule
sync.RWMutex
}
func newRulesTable() *rulesTable {
return &rulesTable{
rulesByHost: make(map[string]*rule),
rulesByShortcut: make(map[string][]*rule),
rulesLeftovers: make([]*rule, 0),
}
}
func (r *rulesTable) Add(rule *rule) {
r.Lock()
if rule.ip != nil {
// Hosts syntax
r.rulesByHost[rule.text] = rule
} else if len(rule.shortcut) == shortcutLength && enableFastLookup {
// Adblock syntax with a shortcut
r.rulesByShortcut[rule.shortcut] = append(r.rulesByShortcut[rule.shortcut], rule)
} else {
// Adblock syntax -- too short to have a shortcut
r.rulesLeftovers = append(r.rulesLeftovers, rule)
}
r.Unlock()
}
func (r *rulesTable) matchByHost(host string) (Result, error) {
// First: examine the hosts-syntax rules
res, err := r.searchByHost(host)
if err != nil {
return res, err
}
if res.Reason.Matched() {
return res, nil
}
// Second: examine the adblock-syntax rules with shortcuts
res, err = r.searchShortcuts(host)
if err != nil {
return res, err
}
if res.Reason.Matched() {
return res, nil
}
// Third: examine the others
res, err = r.searchLeftovers(host)
if err != nil {
return res, err
}
if res.Reason.Matched() {
return res, nil
}
return Result{}, nil
}
func (r *rulesTable) searchByHost(host string) (Result, error) {
rule, ok := r.rulesByHost[host]
if ok {
return rule.match(host)
}
return Result{}, nil
}
func (r *rulesTable) searchShortcuts(host string) (Result, error) {
// check in shortcuts first
for i := 0; i < len(host); i++ {
shortcut := host[i:]
if len(shortcut) > shortcutLength {
shortcut = shortcut[:shortcutLength]
}
if len(shortcut) != shortcutLength {
continue
}
rules, ok := r.rulesByShortcut[shortcut]
if !ok {
continue
}
for _, rule := range rules {
res, err := rule.match(host)
// error? stop search
if err != nil {
return res, err
}
// matched? stop search
if res.Reason.Matched() {
return res, err
}
// continue otherwise
}
}
return Result{}, nil
}
func (r *rulesTable) searchLeftovers(host string) (Result, error) {
for _, rule := range r.rulesLeftovers {
res, err := rule.match(host)
// error? stop search
if err != nil {
return res, err
}
// matched? stop search
if res.Reason.Matched() {
return res, err
}
// continue otherwise
}
return Result{}, nil
}
func findOptionIndex(text string) int {
for i, r := range text {
// ignore non-$
if r != '$' {
continue
}
// ignore `\$`
if i > 0 && text[i-1] == '\\' {
continue
}
// ignore `$/`
if i > len(text) && text[i+1] == '/' {
continue
}
return i + 1
}
return -1
}
func (rule *rule) extractOptions() error {
optIndex := findOptionIndex(rule.text)
if optIndex == 0 { // starts with $
return ErrInvalidSyntax
}
if optIndex == len(rule.text) { // ends with $
return ErrInvalidSyntax
}
if optIndex < 0 {
return nil
}
optionsStr := rule.text[optIndex:]
rule.text = rule.text[:optIndex-1] // remove options from text
begin := 0
i := 0
for i = 0; i < len(optionsStr); i++ {
switch optionsStr[i] {
case ',':
if i > 0 {
// it might be escaped, if so, ignore
if optionsStr[i-1] == '\\' {
break // from switch, not for loop
}
}
rule.options = append(rule.options, optionsStr[begin:i])
begin = i + 1
}
}
if begin != i {
// there's still an option remaining
rule.options = append(rule.options, optionsStr[begin:])
}
return nil
}
func (rule *rule) parseOptions() error {
err := rule.extractOptions()
if err != nil {
return err
}
for _, option := range rule.options {
switch {
case option == "important":
rule.isImportant = true
case strings.HasPrefix(option, "app="):
option = strings.TrimPrefix(option, "app=")
rule.apps = strings.Split(option, "|")
default:
return ErrInvalidSyntax
}
}
return nil
}
func (rule *rule) extractShortcut() {
// regex rules have no shortcuts
if rule.text[0] == '/' && rule.text[len(rule.text)-1] == '/' {
return
}
fields := strings.FieldsFunc(rule.text, func(r rune) bool {
switch r {
case '*', '^', '|':
return true
}
return false
})
longestField := ""
for _, field := range fields {
if len(field) > len(longestField) {
longestField = field
}
}
if len(longestField) > shortcutLength {
longestField = longestField[:shortcutLength]
}
rule.shortcut = strings.ToLower(longestField)
}
func (rule *rule) compile() error {
rule.RLock()
isCompiled := rule.isSuffix || rule.compiled != nil
rule.RUnlock()
if isCompiled {
return nil
}
isSuffix, suffix := getSuffix(rule.text)
if isSuffix {
rule.Lock()
rule.isSuffix = isSuffix
rule.suffix = suffix
rule.Unlock()
return nil
}
expr, err := ruleToRegexp(rule.text)
if err != nil {
return err
}
compiled, err := regexp.Compile(expr)
if err != nil {
return err
}
rule.Lock()
rule.compiled = compiled
rule.Unlock()
return nil
}
// Checks if the rule matches the specified host and returns a corresponding Result object
func (rule *rule) match(host string) (Result, error) {
res := Result{}
if rule.ip != nil && rule.text == host {
// This is a hosts-syntax rule -- just check that the hostname matches and return the result
return Result{
IsFiltered: true,
Reason: FilteredBlackList,
Rule: rule.originalText,
IP: rule.ip,
FilterID: rule.listID,
}, nil
}
err := rule.compile()
if err != nil {
return res, err
}
rule.RLock()
matched := false
if rule.isSuffix {
if host == rule.suffix {
matched = true
} else if strings.HasSuffix(host, "."+rule.suffix) {
matched = true
}
} else {
matched = rule.compiled.MatchString(host)
}
rule.RUnlock()
if matched {
res.Reason = FilteredBlackList
res.IsFiltered = true
res.FilterID = rule.listID
res.Rule = rule.originalText
if rule.isWhitelist {
res.Reason = NotFilteredWhiteList
res.IsFiltered = false
}
}
return res, nil
}
func getCachedReason(cache gcache.Cache, host string) (result Result, isFound bool, err error) {
isFound = false // not found yet
// get raw value
rawValue, err := cache.Get(host)
if err == gcache.KeyNotFoundError {
// not a real error, just not found
err = nil
return
}
if err != nil {
// real error
return
}
// since it can be something else, validate that it belongs to proper type
cachedValue, ok := rawValue.(Result)
if !ok {
// this is not our type -- error
text := "SHOULD NOT HAPPEN: entry with invalid type was found in lookup cache"
log.Println(text)
err = errors.New(text)
return
}
isFound = ok
return cachedValue, isFound, err
}
// for each dot, hash it and add it to string
func hostnameToHashParam(host string, addslash bool) (string, map[string]bool) {
var hashparam bytes.Buffer
hashes := map[string]bool{}
tld, icann := publicsuffix.PublicSuffix(host)
if !icann {
// private suffixes like cloudfront.net
tld = ""
}
curhost := host
for {
if curhost == "" {
// we've reached end of string
break
}
if tld != "" && curhost == tld {
// we've reached the TLD, don't hash it
break
}
tohash := []byte(curhost)
if addslash {
tohash = append(tohash, '/')
}
sum := sha256.Sum256(tohash)
hexhash := fmt.Sprintf("%X", sum)
hashes[hexhash] = true
hashparam.WriteString(fmt.Sprintf("%02X%02X%02X%02X/", sum[0], sum[1], sum[2], sum[3]))
pos := strings.IndexByte(curhost, byte('.'))
if pos < 0 {
break
}
curhost = curhost[pos+1:]
}
return hashparam.String(), hashes
}
func (d *Dnsfilter) checkSafeSearch(host string) (Result, error) {
if safeSearchCache == nil {
safeSearchCache = gcache.New(defaultCacheSize).LRU().Expiration(defaultCacheTime).Build()
}
// Check cache. Return cached result if it was found
cachedValue, isFound, err := getCachedReason(safeSearchCache, host)
if isFound {
atomic.AddUint64(&stats.Safesearch.CacheHits, 1)
return cachedValue, nil
}
if err != nil {
return Result{}, err
}
safeHost, ok := d.SafeSearchDomain(host)
if !ok {
return Result{}, nil
}
res := Result{IsFiltered: true, Reason: FilteredSafeSearch}
if ip := net.ParseIP(safeHost); ip != nil {
res.IP = ip
err = safeSearchCache.Set(host, res)
if err != nil {
return Result{}, nil
}
return res, nil
}
// TODO this address should be resolved with upstream that was configured in dnsforward
addrs, err := net.LookupIP(safeHost)
if err != nil {
log.Tracef("SafeSearchDomain for %s was found but failed to lookup for %s cause %s", host, safeHost, err)
return Result{}, err
}
res.IP = addrs[0]
// The next bug may occurs: LookupIP returns DNS64 mapped ipv4 address with zero-prefix
for _, i := range addrs {
if ipv4 := i.To4(); ipv4 != nil && len(i) == net.IPv6len {
res.IP = ipv4
break
}
}
// Cache result
err = safeSearchCache.Set(host, res)
if err != nil {
return Result{}, nil
}
return res, nil
}
func (d *Dnsfilter) checkSafeBrowsing(host string) (Result, error) {
// prevent recursion -- checking the host of safebrowsing server makes no sense
if host == d.safeBrowsingServer {
return Result{}, nil
}
format := func(hashparam string) string {
url := fmt.Sprintf(defaultSafebrowsingURL, d.safeBrowsingServer, hashparam)
return url
}
handleBody := func(body []byte, hashes map[string]bool) (Result, error) {
result := Result{}
scanner := bufio.NewScanner(strings.NewReader(string(body)))
for scanner.Scan() {
line := scanner.Text()
splitted := strings.Split(line, ":")
if len(splitted) < 3 {
continue
}
hash := splitted[2]
if _, ok := hashes[hash]; ok {
// it's in the hash
result.IsFiltered = true
result.Reason = FilteredSafeBrowsing
result.Rule = splitted[0]
break
}
}
if err := scanner.Err(); err != nil {
// error, don't save cache
return Result{}, err
}
return result, nil
}
if safebrowsingCache == nil {
safebrowsingCache = gcache.New(defaultCacheSize).LRU().Expiration(defaultCacheTime).Build()
}
result, err := d.lookupCommon(host, &stats.Safebrowsing, safebrowsingCache, true, format, handleBody)
return result, err
}
func (d *Dnsfilter) checkParental(host string) (Result, error) {
// prevent recursion -- checking the host of parental safety server makes no sense
if host == d.parentalServer {
return Result{}, nil
}
format := func(hashparam string) string {
url := fmt.Sprintf(defaultParentalURL, d.parentalServer, hashparam, d.ParentalSensitivity)
return url
}
handleBody := func(body []byte, hashes map[string]bool) (Result, error) {
// parse json
var m []struct {
Blocked bool `json:"blocked"`
ClientTTL int `json:"clientTtl"`
Reason string `json:"reason"`
Hash string `json:"hash"`
}
err := json.Unmarshal(body, &m)
if err != nil {
// error, don't save cache
log.Printf("Couldn't parse json '%s': %s", body, err)
return Result{}, err
}
result := Result{}
for i := range m {
if !hashes[m[i].Hash] {
continue
}
if m[i].Blocked {
result.IsFiltered = true
result.Reason = FilteredParental
result.Rule = fmt.Sprintf("parental %s", m[i].Reason)
break
}
}
return result, nil
}
if parentalCache == nil {
parentalCache = gcache.New(defaultCacheSize).LRU().Expiration(defaultCacheTime).Build()
}
result, err := d.lookupCommon(host, &stats.Parental, parentalCache, false, format, handleBody)
return result, err
}
type formatHandler func(hashparam string) string
type bodyHandler func(body []byte, hashes map[string]bool) (Result, error)
// real implementation of lookup/check
func (d *Dnsfilter) lookupCommon(host string, lookupstats *LookupStats, cache gcache.Cache, hashparamNeedSlash bool, format formatHandler, handleBody bodyHandler) (Result, error) {
// if host ends with a dot, trim it
host = strings.ToLower(strings.Trim(host, "."))
// check cache
cachedValue, isFound, err := getCachedReason(cache, host)
if isFound {
atomic.AddUint64(&lookupstats.CacheHits, 1)
return cachedValue, nil
}
if err != nil {
return Result{}, err
}
// convert hostname to hash parameters
hashparam, hashes := hostnameToHashParam(host, hashparamNeedSlash)
// format URL with our hashes
url := format(hashparam)
// do HTTP request
atomic.AddUint64(&lookupstats.Requests, 1)
atomic.AddInt64(&lookupstats.Pending, 1)
updateMax(&lookupstats.Pending, &lookupstats.PendingMax)
resp, err := d.client.Get(url)
atomic.AddInt64(&lookupstats.Pending, -1)
if resp != nil && resp.Body != nil {
defer resp.Body.Close()
}
if err != nil {
// error, don't save cache
return Result{}, err
}
// get body text
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
// error, don't save cache
return Result{}, err
}
// handle status code
switch {
case resp.StatusCode == 204:
// empty result, save cache
err = cache.Set(host, Result{})
if err != nil {
return Result{}, err
}
return Result{}, nil
case resp.StatusCode != 200:
// error, don't save cache
return Result{}, nil
}
result, err := handleBody(body, hashes)
if err != nil {
// error, don't save cache
return Result{}, err
}
err = cache.Set(host, result)
if err != nil {
return Result{}, err
}
return result, nil
}
//
// Adding rule and matching against the rules
//
// AddRules is a convinience function to add an array of filters in one call
func (d *Dnsfilter) AddRules(filters []Filter) error {
for _, f := range filters {
for _, rule := range f.Rules {
err := d.AddRule(rule, f.ID)
if err == ErrAlreadyExists || err == ErrInvalidSyntax {
continue
}
if err != nil {
log.Printf("Cannot add rule %s: %s", rule, err)
// Just ignore invalid rules
continue
}
}
}
return nil
}
// AddRule adds a rule, checking if it is a valid rule first and if it wasn't added already
func (d *Dnsfilter) AddRule(input string, filterListID int64) error {
input = strings.TrimSpace(input)
d.storageMutex.RLock()
_, exists := d.storage[input]
d.storageMutex.RUnlock()
if exists {
// already added
return ErrAlreadyExists
}
if !isValidRule(input) {
return ErrInvalidSyntax
}
// First, check if this is a hosts-syntax rule
if d.parseEtcHosts(input, filterListID) {
// This is a valid hosts-syntax rule, no need for further parsing
return nil
}
// Start parsing the rule
r := rule{
text: input, // will be modified
originalText: input,
listID: filterListID,
}
// Mark rule as whitelist if it starts with @@
if strings.HasPrefix(r.text, "@@") {
r.isWhitelist = true
r.text = r.text[2:]
}
err := r.parseOptions()
if err != nil {
return err
}
r.extractShortcut()
if !enableDelayedCompilation {
err := r.compile()
if err != nil {
return err
}
}
destination := d.blackList
if r.isImportant {
destination = d.important
} else if r.isWhitelist {
destination = d.whiteList
}
d.storageMutex.Lock()
d.storage[input] = true
d.storageMutex.Unlock()
destination.Add(&r)
return nil
}
// Parses the hosts-syntax rules. Returns false if the input string is not of hosts-syntax.
func (d *Dnsfilter) parseEtcHosts(input string, filterListID int64) bool {
// Strip the trailing comment
ruleText := input
if pos := strings.IndexByte(ruleText, '#'); pos != -1 {
ruleText = ruleText[0:pos]
}
fields := strings.Fields(ruleText)
if len(fields) < 2 {
return false
}
addr := net.ParseIP(fields[0])
if addr == nil {
return false
}
d.storageMutex.Lock()
d.storage[input] = true
d.storageMutex.Unlock()
for _, host := range fields[1:] {
r := rule{
text: host,
originalText: input,
listID: filterListID,
ip: addr,
}
d.blackList.Add(&r)
}
return true
}
// matchHost is a low-level way to check only if hostname is filtered by rules, skipping expensive safebrowsing and parental lookups
func (d *Dnsfilter) matchHost(host string) (Result, error) {
lists := []*rulesTable{
d.important,
d.whiteList,
d.blackList,
}
for _, table := range lists {
res, err := table.matchByHost(host)
if err != nil {
return res, err
}
if res.Reason.Matched() {
return res, nil
}
}
return Result{}, nil
}
//
// lifecycle helper functions
//
// New creates properly initialized DNS Filter that is ready to be used
func New(c *Config) *Dnsfilter {
d := new(Dnsfilter)
d.storage = make(map[string]bool)
d.important = newRulesTable()
d.whiteList = newRulesTable()
d.blackList = newRulesTable()
// Customize the Transport to have larger connection pool,
// We are not (re)using http.DefaultTransport because of race conditions found by tests
d.transport = &http.Transport{
Proxy: http.ProxyFromEnvironment,
MaxIdleConns: defaultHTTPMaxIdleConnections, // default 100
MaxIdleConnsPerHost: defaultHTTPMaxIdleConnections, // default 2
IdleConnTimeout: 90 * time.Second,
TLSHandshakeTimeout: 10 * time.Second,
ExpectContinueTimeout: 1 * time.Second,
}
d.client = http.Client{
Transport: d.transport,
Timeout: defaultHTTPTimeout,
}
d.safeBrowsingServer = defaultSafebrowsingServer
d.parentalServer = defaultParentalServer
if c != nil {
d.Config = *c
}
return d
}
// Destroy is optional if you want to tidy up goroutines without waiting for them to die off
// right now it closes idle HTTP connections if there are any
func (d *Dnsfilter) Destroy() {
if d != nil && d.transport != nil {
d.transport.CloseIdleConnections()
}
}
//
// config manipulation helpers
//
// SetSafeBrowsingServer lets you optionally change hostname of safesearch lookup
func (d *Dnsfilter) SetSafeBrowsingServer(host string) {
if len(host) == 0 {
d.safeBrowsingServer = defaultSafebrowsingServer
} else {
d.safeBrowsingServer = host
}
}
// SetHTTPTimeout lets you optionally change timeout during lookups
func (d *Dnsfilter) SetHTTPTimeout(t time.Duration) {
d.client.Timeout = t
}
// ResetHTTPTimeout resets lookup timeouts
func (d *Dnsfilter) ResetHTTPTimeout() {
d.client.Timeout = defaultHTTPTimeout
}
// SafeSearchDomain returns replacement address for search engine
func (d *Dnsfilter) SafeSearchDomain(host string) (string, bool) {
if d.SafeSearchEnabled {
val, ok := safeSearchDomains[host]
return val, ok
}
return "", false
}
//
// stats
//
// GetStats return dns filtering stats since startup
func (d *Dnsfilter) GetStats() Stats {
return stats
}
// Count returns number of rules added to filter
func (d *Dnsfilter) Count() int {
return len(d.storage)
}