commit b789e719affbb0a6ff9c22095f6ca8db6a5f4926
Author: Eduard Bagdasaryan <eduard.bagdasaryan@measurement-factory.com>
Date:   2020-07-27 15:28:31 +0000

    Fix livelocking in peerDigestHandleReply (#698)
    
    peerDigestHandleReply() was missing a premature EOF check. The existing
    peerDigestFetchedEnough() cannot detect EOF because it does not have
    access to receivedData.length used to indicate the EOF condition. We did
    not adjust peerDigestFetchedEnough() because it is abused to check both
    post-I/O state and the state after each digest processing step. The
    latter invocations lack access to receivedData.length and should not
    really bother with EOF anyway.

diff --git a/src/peer_digest.cc b/src/peer_digest.cc
index d48340f97..265f16183 100644
--- a/src/peer_digest.cc
+++ b/src/peer_digest.cc
@@ -483,6 +483,15 @@ peerDigestHandleReply(void *data, StoreIOBuffer receivedData)
 
     } while (cbdataReferenceValid(fetch) && prevstate != fetch->state && fetch->bufofs > 0);
 
+    // Check for EOF here, thus giving the parser one extra run. We could avoid this overhead by
+    // checking at the beginning of this function. However, in this case, we would have to require
+    // that the parser does not regard EOF as a special condition (it is true now but may change
+    // in the future).
+    if (!receivedData.length) { // EOF
+        peerDigestFetchAbort(fetch, fetch->buf, "premature end of digest reply");
+        return;
+    }
+
     /* Update the copy offset */
     fetch->offset += receivedData.length;