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commit b789e719affbb0a6ff9c22095f6ca8db6a5f4926
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Author: Eduard Bagdasaryan <eduard.bagdasaryan@measurement-factory.com>
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Date: 2020-07-27 15:28:31 +0000
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Fix livelocking in peerDigestHandleReply (#698)
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peerDigestHandleReply() was missing a premature EOF check. The existing
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peerDigestFetchedEnough() cannot detect EOF because it does not have
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access to receivedData.length used to indicate the EOF condition. We did
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not adjust peerDigestFetchedEnough() because it is abused to check both
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post-I/O state and the state after each digest processing step. The
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latter invocations lack access to receivedData.length and should not
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really bother with EOF anyway.
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diff --git a/src/peer_digest.cc b/src/peer_digest.cc
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index d48340f97..265f16183 100644
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--- a/src/peer_digest.cc
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+++ b/src/peer_digest.cc
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@@ -483,6 +483,15 @@ peerDigestHandleReply(void *data, StoreIOBuffer receivedData)
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} while (cbdataReferenceValid(fetch) && prevstate != fetch->state && fetch->bufofs > 0);
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+ // Check for EOF here, thus giving the parser one extra run. We could avoid this overhead by
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+ // checking at the beginning of this function. However, in this case, we would have to require
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+ // that the parser does not regard EOF as a special condition (it is true now but may change
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+ // in the future).
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+ if (!receivedData.length) { // EOF
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+ peerDigestFetchAbort(fetch, fetch->buf, "premature end of digest reply");
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+ return;
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+ }
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+
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/* Update the copy offset */
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fetch->offset += receivedData.length;
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