miracle091/dnscrypt-proxy
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dnscrypt-proxy
mirror of https://github.com/DNSCrypt/dnscrypt-proxy.git
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Infer TTL from Date: and Expire: headers 

Unfortunately, Google DNS sets Expire: to the same value as Date:

So we may want to use Cache-Control instead.
This commit is contained in:
Frank Denis 2018-02-04 13:35:40 +01:00
parent 458da8fa77
commit ed60976dd2
2 changed files with 34 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
dnscrypt-proxy/plugins.go
View File

@ -148,7 +148,7 @@ func (pluginsState *PluginsState) ApplyQueryPlugins(pluginsGlobals *PluginsGloba
return packet2, nil
}
func (pluginsState *PluginsState) ApplyResponsePlugins(pluginsGlobals *PluginsGlobals, packet []byte) ([]byte, error) {
func (pluginsState *PluginsState) ApplyResponsePlugins(pluginsGlobals *PluginsGlobals, packet []byte, ttl *uint32) ([]byte, error) {
if len(*pluginsGlobals.responsePlugins) == 0 {
return packet, nil
}
@ -177,6 +177,9 @@ func (pluginsState *PluginsState) ApplyResponsePlugins(pluginsGlobals *PluginsGl
}
}
pluginsGlobals.RUnlock()
if ttl != nil {
setMaxTTL(&msg, *ttl)
}
packet2, err := msg.PackBuffer(packet)
if err != nil {
return packet, err

31
dnscrypt-proxy/proxy.go
View File

@ -5,6 +5,7 @@ import (
"io/ioutil"
"math/rand"
"net"
"net/http"
"sync/atomic"
"time"
@ -263,6 +264,7 @@ func (proxy *Proxy) processIncomingQuery(serverInfo *ServerInfo, clientProto str
}
}
if len(response) == 0 {
var ttl *uint32
if serverInfo.Proto == StampProtoTypeDNSCrypt {
encryptedQuery, clientNonce, err := proxy.Encrypt(serverInfo, query, serverProto)
if err != nil {
@ -293,6 +295,7 @@ func (proxy *Proxy) processIncomingQuery(serverInfo *ServerInfo, clientProto str
if len(response) >= MinDNSPacketSize {
SetTransactionID(response, tid)
}
ttl = ttlFromHTTPResponse(proxy, resp)
} else {
dlog.Fatal("Unsupported protocol")
}
@ -300,7 +303,7 @@ func (proxy *Proxy) processIncomingQuery(serverInfo *ServerInfo, clientProto str
serverInfo.noticeFailure(proxy)
return
}
response, _ = pluginsState.ApplyResponsePlugins(&proxy.pluginsGlobals, response)
response, _ = pluginsState.ApplyResponsePlugins(&proxy.pluginsGlobals, response, ttl)
}
if len(response) < MinDNSPacketSize || len(response) > MaxDNSPacketSize {
serverInfo.noticeFailure(proxy)
@ -329,3 +332,29 @@ func (proxy *Proxy) processIncomingQuery(serverInfo *ServerInfo, clientProto str
}
serverInfo.noticeSuccess(proxy)
}
func ttlFromHTTPResponse(proxy *Proxy, resp *http.Response) *uint32 {
expiresStr, dateStr := resp.Header.Get("Expires"), resp.Header.Get("Date")
if len(expiresStr) == 0 || len(dateStr) == 0 {
return nil
}
expires, err := http.ParseTime(expiresStr)
if err != nil {
return nil
}
date, err := http.ParseTime(dateStr)
if err != nil {
return nil
}
if !expires.After(date) {
return nil
}
foundTTL := uint32(expires.Sub(date).Seconds())
if foundTTL < proxy.cacheMaxTTL {
foundTTL = proxy.cacheMinTTL
}
if foundTTL > proxy.cacheMaxTTL {
foundTTL = proxy.cacheMaxTTL
}
return &foundTTL
}