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client_names_resolver.go
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client_names_resolver.go
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package resolver
import (
"fmt"
"net"
"strings"
"time"
"github.com/0xERR0R/blocky/cache/expirationcache"
"github.com/0xERR0R/blocky/config"
"github.com/0xERR0R/blocky/model"
"github.com/0xERR0R/blocky/util"
"github.com/miekg/dns"
"github.com/sirupsen/logrus"
)
// ClientNamesResolver tries to determine client name by asking responsible DNS server via rDNS (reverse lookup)
type ClientNamesResolver struct {
cache expirationcache.ExpiringCache
externalResolver Resolver
singleNameOrder []uint
clientIPMapping map[string][]net.IP
NextResolver
}
// NewClientNamesResolver creates new resolver instance
func NewClientNamesResolver(
cfg config.ClientLookupConfig, bootstrap *Bootstrap, shouldVerifyUpstreams bool,
) (cr *ClientNamesResolver, err error) {
var r Resolver
if !cfg.Upstream.IsDefault() {
r, err = NewUpstreamResolver(cfg.Upstream, bootstrap, shouldVerifyUpstreams)
if err != nil {
return nil, err
}
}
cr = &ClientNamesResolver{
cache: expirationcache.NewCache(expirationcache.WithCleanUpInterval(time.Hour)),
externalResolver: r,
singleNameOrder: cfg.SingleNameOrder,
clientIPMapping: cfg.ClientnameIPMapping,
}
return
}
// Configuration returns current resolver configuration
func (r *ClientNamesResolver) Configuration() (result []string) {
if r.externalResolver == nil && len(r.clientIPMapping) == 0 {
return append(configDisabled, "use only IP address")
}
result = append(result, fmt.Sprintf("singleNameOrder = \"%v\"", r.singleNameOrder))
if r.externalResolver != nil {
result = append(result, fmt.Sprintf("externalResolver = \"%s\"", r.externalResolver))
}
result = append(result, fmt.Sprintf("cache item count = %d", r.cache.TotalCount()))
if len(r.clientIPMapping) > 0 {
result = append(result, "client IP mapping:")
for k, v := range r.clientIPMapping {
result = append(result, fmt.Sprintf("%s -> %s", k, v))
}
}
return
}
// Resolve tries to resolve the client name from the ip address
func (r *ClientNamesResolver) Resolve(request *model.Request) (*model.Response, error) {
clientNames := r.getClientNames(request)
request.ClientNames = clientNames
request.Log = request.Log.WithField("client_names", strings.Join(clientNames, "; "))
return r.next.Resolve(request)
}
// returns names of client
func (r *ClientNamesResolver) getClientNames(request *model.Request) []string {
if request.RequestClientID != "" {
return []string{request.RequestClientID}
}
ip := request.ClientIP
if ip == nil {
return []string{}
}
c, _ := r.cache.Get(ip.String())
if c != nil {
if t, ok := c.([]string); ok {
return t
}
}
names := r.resolveClientNames(ip, withPrefix(request.Log, "client_names_resolver"))
r.cache.Put(ip.String(), names, time.Hour)
return names
}
func extractClientNamesFromAnswer(answer []dns.RR, fallbackIP net.IP) (clientNames []string) {
for _, answer := range answer {
if t, ok := answer.(*dns.PTR); ok {
hostName := strings.TrimSuffix(t.Ptr, ".")
clientNames = append(clientNames, hostName)
}
}
if len(clientNames) == 0 {
clientNames = []string{fallbackIP.String()}
}
return
}
// tries to resolve client name from mapping, performs reverse DNS lookup otherwise
func (r *ClientNamesResolver) resolveClientNames(ip net.IP, logger *logrus.Entry) (result []string) {
// try client mapping first
result = r.getNameFromIPMapping(ip, result)
if len(result) > 0 {
return
}
if r.externalResolver == nil {
return []string{ip.String()}
}
reverse, _ := dns.ReverseAddr(ip.String())
resp, err := r.externalResolver.Resolve(&model.Request{
Req: util.NewMsgWithQuestion(reverse, dns.Type(dns.TypePTR)),
Log: logger,
})
if err != nil {
logger.Error("can't resolve client name: ", err)
return []string{ip.String()}
}
clientNames := extractClientNamesFromAnswer(resp.Res.Answer, ip)
// optional: if singleNameOrder is set, use only one name in the defined order
if len(r.singleNameOrder) > 0 {
for _, i := range r.singleNameOrder {
if i > 0 && int(i) <= len(clientNames) {
result = []string{clientNames[i-1]}
break
}
}
} else {
result = clientNames
}
logger.WithField("client_names", strings.Join(result, "; ")).Debug("resolved client name(s) from external resolver")
return result
}
func (r *ClientNamesResolver) getNameFromIPMapping(ip net.IP, result []string) []string {
for name, ips := range r.clientIPMapping {
for _, i := range ips {
if ip.String() == i.String() {
result = append(result, name)
}
}
}
return result
}
// FlushCache reset client name cache
func (r *ClientNamesResolver) FlushCache() {
r.cache.Clear()
}