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Add a grace TTL for expired cached IPs

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And some comments to make the code more readable
This commit is contained in:
Frank Denis 2019-11-01 23:19:07 +01:00
parent 0dc69eacd5
commit 6032c3b79b
1 changed files with 6 additions and 2 deletions
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8
dnscrypt-proxy/xtransport.go
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@ -30,6 +30,7 @@ const (
DefaultKeepAlive = 5 * time.Second
DefaultTimeout = 30 * time.Second
SystemResolverTTL = 24 * time.Hour
ExpiredCachedIPGraceTTL = 1 * time.Minute
)
type CachedIPItem struct {
@ -98,8 +99,7 @@ func (xTransport *XTransport) saveCachedIP(host string, ip net.IP, ttl time.Dura
}
func (xTransport *XTransport) loadCachedIP(host string) (ip net.IP, expired bool) {
ip = nil
expired = false
ip, expired = nil, false
xTransport.cachedIPs.RLock()
item, ok := xTransport.cachedIPs.cache[host]
xTransport.cachedIPs.RUnlock()
@ -131,6 +131,8 @@ func (xTransport *XTransport) rebuildTransport() {
DialContext: func(ctx context.Context, network, addrStr string) (net.Conn, error) {
host, port := ExtractHostAndPort(addrStr, stamps.DefaultPort)
ipOnly := host
// resolveWithCache() is always called in `Fetch()` before the `Dial()`
// method is used, so that a cached entry must be present at this point.
cachedIP, _ := xTransport.loadCachedIP(host)
if cachedIP == nil {
if ipv4 := cachedIP.To4(); ipv4 != nil {
@ -242,6 +244,7 @@ func (xTransport *XTransport) resolveUsingResolver(proto, host string, resolver
return
}
// Return a cached entry, or resolve a name and update the cache
func (xTransport *XTransport) resolveWithCache(host string) (err error) {
if xTransport.proxyDialer != nil || xTransport.httpProxyFunction != nil {
return
@ -278,6 +281,7 @@ func (xTransport *XTransport) resolveWithCache(host string) (err error) {
if err != nil {
if cachedIP != nil {
foundIP = cachedIP
ttl = ExpiredCachedIPGraceTTL
} else {
return
}