[#1800] Make ipfs.getFromDatastore IpnsEntry unmarshal fail gracefully

If any record is returned that fails to unmarshal into an pb.IpnsEntry,
the error bubbles all the way up without properly checking the
alternative key prefixes.

Author: placer14

ipfs/resolve.go

@@ -2,6 +2,8 @@ package ipfs
 
 import (
 	"context"
+	"fmt"
+	"runtime/debug"
 	"time"
 
 	ipath "gx/ipfs/QmQAgv6Gaoe2tQpcabqwKXKChp2MZ7i3UXv9DqTTaxCaTR/go-path"
@@ -99,30 +101,41 @@ func ResolveAltRoot(n *core.IpfsNode, p peer.ID, altRoot string, timeout time.Du
 // under /ipns/persistentcache/<peerID> which returns only the value (the path)
 // inside the protobuf record.
 func getFromDatastore(datastore ds.Datastore, p peer.ID) (ipath.Path, error) {
-	ival, err := datastore.Get(nativeIPNSRecordCacheKey(p))
-	if err != nil {
-		pth, err := datastore.Get(persistentCacheKey(p))
-		if err != nil {
-			if err == ds.ErrNotFound {
-				return "", namesys.ErrResolveFailed
-			}
-			return "", err
-		}
-		return ipath.ParsePath(string(pth))
+	rec, err := getCachedIPNSRecord(datastore, p)
+	if err == nil {
+		return ipath.ParsePath(string(rec.Value))
 	}
 
-	rec := new(ipnspb.IpnsEntry)
-	err = proto.Unmarshal(ival, rec)
+	pth, err := datastore.Get(persistentCacheKey(p))
 	if err != nil {
-		return "", err
+		if err == ds.ErrNotFound {
+			return "", namesys.ErrResolveFailed
+		}
+		return "", fmt.Errorf("getting cached ipns path: %s", err.Error())
 	}
-	return ipath.ParsePath(string(rec.Value))
+	return ipath.ParsePath(string(pth))
 }
 
 func putToDatastoreCache(datastore ds.Datastore, p peer.ID, pth ipath.Path) error {
 	return datastore.Put(persistentCacheKey(p), []byte(pth.String()))
 }
 
+// getCachedIPNSRecord retrieves the full IPNSEntry from the provided datastore if present
+func getCachedIPNSRecord(store ds.Datastore, id peer.ID) (*ipnspb.IpnsEntry, error) {
+	ival, err := store.Get(nativeIPNSRecordCacheKey(id))
+	if err != nil {
+		return nil, fmt.Errorf("getting cached ipns record: %s", err.Error())
+	}
+	rec := new(ipnspb.IpnsEntry)
+	err = proto.Unmarshal(ival, rec)
+	if err != nil {
+		log.Errorf("failed parsing cached record for peer (%s): %s", id.Pretty(), err.Error())
+		log.Debug(debug.Stack())
+		return nil, fmt.Errorf("parsing cached ipns record: %s", err.Error())
+	}
+	return rec, nil
+}
+
 // PutCachedPubkey persists the pubkey using the appropriate key prefix
 // from the provided datastore
 func PutCachedPubkey(store ds.Datastore, peerID string, pubkey []byte) error {