-Change all print statements to log.msg() calls.
+Rotate DNS entries for mirrors more reliably.
+Currently the mirrors are accessed by DNS name, which can cause some
+issues when there are mirror differences and the DNS gets rotated.
+Instead, the HTTP Downloader should handle DNS lookups itself, store
+the resulting addresses, and send requests to IP addresses. If there
+is an error from the mirror (hash check or 404 response), the next IP
+address in the rotation should be used.
-Add ability to search and hash and DHT-store other directories.
-The user should be able to specify a list of directories that will be
-searched for files to hash and add to the DHT.
+Use GPG signatures as a hash for files.
+A detached GPG signature, such as is found in Release.gpg, can be used
+as a hash for the file. This hash can be used to verify the file when
+it is downloaded, and a shortened version can be added to the DHT to
+look up peers for the file. To get the hash into a binary form from
+the ascii-armored detached file, use the command
+'gpg --no-options --no-default-keyring --output - --dearmor -'. The
+hash should be stored as the reverse of the resulting binary string,
+as the bytes at the beginning are headers that are the same for most
+signatures. That way the shortened hash stored in the DHT will have a
+better chance of being unique and being stored on different peers. To
+verify a file, first the binary hash must be re-reversed, armored, and
+written to a temporary file with the command
+'gpg --no-options --no-default-keyring --output $tempfile --enarmor -'.
+Then the incoming file can be verified with the command
+'gpg --no-options --no-default-keyring --keyring /etc/apt/trusted.gpg
+--verify $tempfile -'.
-Missing Kademlia implementation details are needed.
+All communication with the command-line gpg should be done using pipes
+and the python module python-gnupginterface. There needs to be a new
+module for GPG verification and hashing, which will make this easier.
+In particular, it would need to support hashlib-like functionality
+such as new(), update(), and digest(). Note that the verification
+would not involve signing the file again and comparing the signatures,
+as this is not possible. Instead, the verify() function would have to
+behave differently for GPG hashes, and check that the verification
+resulted in a VALIDSIG. CAUTION: the detached signature can have a
+variable length, though it seems to be usually 65 bytes, 64 bytes has
+also been observed.
-The current implementation is missing some important features, mostly
-focussed on storing values:
- - values need to be republished (every hour?)
- - original publishers need to republish values (every 24 hours)
- - when a new node is found that is closer to some values, replicate the
- values there without deleting them
- - when a value lookup succeeds, store the value in the closest node
- found that didn't have it
- - make the expiration time of a value exponentially inversely
- proportional to the number of nodes between the current node and the
- node closest to the value
+
+Consider what happens when multiple requests for a file are received.
+
+When another request comes in for a file already being downloaded,
+the new request should wait for the old one to finish. This should
+also be done for multiple requests for peer downloads of files with
+the same hash.
+
+
+Packages.diff files need to be considered.
+
+The Packages.diff/Index files contain hashes of Packages.diff/rred.gz
+files, which themselves contain diffs to the Packages files previously
+downloaded. Apt will request these files for the testing/unstable
+distributions. They need to be dealt with properly by
+adding them to the tracking done by the AptPackages module.
+
+
+Improve the estimation of the total number of nodes
+
+The current total nodes estimation is based on the number of buckets.
+A better way is to look at the average inter-node spacing for the K
+closest nodes after a find_node/value completes. Be sure to measure
+the inter-node spacing in log2 space to dampen any ill effects. This
+can be used in the formula:
+ nodes = 2^160 / 2^(average of log2 spacing)
+The average should also be saved using an exponentially weighted
+moving average (of the log2 distance) over separate find_node/value
+actions to get a better calculation over time.
+
+
+Improve the downloaded and uploaded data measurements.
+
+There are 2 places that this data is measured: for statistics, and for
+limiting the upload bandwidth. They both have deficiencies as they
+sometimes miss the headers or the requests sent out. The upload
+bandwidth calculation only considers the stream in the upload and not
+the headers sent, and it also doesn't consider the upload bandwidth
+from requesting downloads from peers (though that may be a good thing).
+The statistics calculations for downloads include the headers of
+downloaded files, but not the requests received from peers for upload
+files. The statistics for uploaded data only includes the files sent
+and not the headers, and also misses the requests for downloads sent to
+other peers.
+
+
+Rehash changed files instead of removing them.
+
+When the modification time of a file changes but the size does not,
+the file could be rehased to verify it is the same instead of
+automatically removing it. The DB would have to be modified to return
+deferred's for a lot of its functions.
+
+
+Consider storing deltas of packages.
+
+Instead of downloading full package files when a previous version of
+the same package is available, peers could request a delta of the
+package to the previous version. This would only be done if the delta
+is significantly (>50%) smaller than the full package, and is not too
+large (absolutely). A peer that has a new package and an old one would
+add a list of deltas for the package to the value stored in the DHT.
+The delta information would specify the old version (by hash), the
+size of the delta, and the hash of the delta. A peer that has the same
+old package could then download the delta from the peer by requesting
+the hash of the delta. Alternatively, very small deltas could be
+stored directly in the DHT.
+
+
+Consider tracking security issues with packages.
+
+Since sharing information with others about what packages you have
+downloaded (and probably installed) is a possible security
+vulnerability, it would be advantageous to not share that information
+for packages that have known security vulnerabilities. This would
+require some way of obtaining a list of which packages (and versions)
+are vulnerable, which is not currently available.
+
+
+Consider adding peer characteristics to the DHT.
+
+Bad peers could be indicated in the DHT by adding a new value that is
+the NOT of their ID (so they are guaranteed not to store it) indicating
+information about the peer. This could be bad votes on the peer, as
+otherwise a peer could add good info about itself.
+
+
+Consider adding pieces to the DHT instead of files.
+
+Instead of adding file hashes to the DHT, only piece hashes could be
+added. This would allow a peer to upload to other peers while it is
+still downloading the rest of the file. It is not clear that this is
+needed, since peer's will not be uploading and downloading ery much of
+the time.
projects / quix0rs-apt-p2p.git / blobdiff