miracle091/dnscrypt-proxy
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Code Issues Releases Wiki Activity

Reduce the chances of corrupting the cache

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Write both parts of the cache to their temp files before renaming
Now only the 2nd rename failing can leave the cache in a bad state.
This commit is contained in:
William Elwood 2019-11-02 04:36:33 +00:00 committed by Frank Denis
parent b6d11b4351
commit 5ed7b7c24f
1 changed files with 22 additions and 12 deletions
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34
dnscrypt-proxy/sources.go
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@ -79,21 +79,25 @@ func (source *Source) fetchFromCache(now time.Time) (delay time.Duration, err er
func (source *Source) writeToCache(bin, sig []byte) (err error) {
f := source.cacheFile
defer func() {
if err != nil {
if absPath, err2 := filepath.Abs(f); err2 == nil {
f = absPath
}
dlog.Warnf("%s: %s", f, err)
}
}()
if err = safefile.WriteFile(f, bin, 0644); err != nil {
var fSrc, fSig *safefile.File
if fSrc, err = safefile.Create(f, 0644); err != nil {
return
}
if err = safefile.WriteFile(f+".minisig", sig, 0644); err != nil {
defer fSrc.Close()
if fSig, err = safefile.Create(f+".minisig", 0644); err != nil {
return
}
return
defer fSig.Close()
if _, err = fSrc.Write(bin); err != nil {
return
}
if _, err = fSig.Write(sig); err != nil {
return
}
if err = fSrc.Commit(); err != nil {
return
}
return fSig.Commit()
}
func (source *Source) parseURLs(urls []string) {
@ -155,7 +159,13 @@ func (source *Source) fetchWithCache(xTransport *XTransport, now time.Time) (del
return
}
source.in = bin
source.writeToCache(bin, sig) // ignore error: not fatal
if writeErr := source.writeToCache(bin, sig); writeErr != nil { // an error here isn't fatal
f := source.cacheFile
if absPath, absErr := filepath.Abs(f); absErr == nil {
f = absPath
}
dlog.Warnf("%s: %s", f, writeErr)
}
delay = source.prefetchDelay
return
}