-Files for which a hash cannot be found should not be added to the DHT.
+Use python-debian for parsing RFC 822 files.
-If the hash can't found, it stands to reason that other peers will not
-be able to find the hash either. So adding those files to the DHT will
-just clutter it with useless information. Examples include Release.gpg,
-Release, Translation-de.bz2, and Contents.gz.
+There are already routines for parsing these files, so there is no need
+to write more. In the AptPackages, change the Release file parsing to
+use the python-debian routines.
Packages.diff files need to be considered.
adding them to the tracking done by the AptPackages module.
-Hashes need to be sent with requests for some files.
-
-Some files can change without changing the file name, since the file was
-added to the DHT by the peer. Examples are Release, Packages.gz, and
-Sources.bz2. For files like this (and only for files like this), the
-request to download from the peer should include the downloader's
-expected hash for the file as a new HTTP header. If the file is found,
-the cached hash for the file will be used to determine whether the
-request is for the same file as is currently available, and a special
-HTTP response can be sent if it is not (i.e. not a 404).
-
-Alternatively, consider sharing the files by hash instead of by
-directory. Then the request would be for
-http://127.3.45.9:9977/<urlencodedHash>, and it would always work. This
-would require a database lookup for every request.
-
-
PeerManager needs to download large files from multiple peers.
The PeerManager currently chooses a peer at random from the list of
consensus revealing the misbehaving peer.
-Consider storing torrent-like strings in the DHT.
+Store and share torrent-like strings for large files.
-Instead of only storing the file download location (which would still be
+In addition to storing the file download location (which would still be
used for small files), a bencoded dictionary containing the peer's
hashes of the individual pieces could be stored for the larger files
-(20% of all the files are larger than 512 KB ). This dictionary would
-have the download location, a list of the piece sizes, and a list of the
-piece hashes (bittorrent uses a single string of length 20*#pieces, but
-for general non-sha1 case a list is needed).
-
-These piece hashes could be compared ahead of time to determine which
-peers have the same piece hashes (they all should), and then used during
-the download to verify the downloaded pieces.
-
-Alternatively, the peers could store the torrent-like string for large
-files separately, and only contain a reference to it in their stored
-value for the hash of the file. The reference would be a hash of the
-bencoded dictionary, and a lookup of that hash in the DHT would give the
-torrent-like string. (A 100 MB file would result in 200 hashes, which
-would create a bencoded dictionary larger than 6000 bytes.)
+(20% of all the files are larger than 512 KB). This dictionary would
+have the normal piece size, the hash length, and a string containing the
+piece hashes of length <hash length>*<#pieces>. These piece hashes could
+be compared ahead of time to determine which peers have the same piece
+hashes (they all should), and then used during the download to verify
+the downloaded pieces.
+
+For very large files (5 or more pieces), the torrent strings are too
+long to store in the DHT and retrieve (a single UDP packet should be
+less than 1472 bytes to avoid fragmentation). Instead, the peers should
+store the torrent-like string for large files separately, and only
+contain a reference to it in their stored value for the hash of the
+file. The reference would be a hash of the bencoded dictionary. If the
+torrent-like string is short enough to store in the DHT (i.e. less than
+1472 bytes, or about 70 pieces for the SHA1 hash), then a
+lookup of that hash in the DHT would give the torrent-like string.
+Otherwise, a request to the peer for the hash (just like files are
+downloaded), should return the bencoded torrent-like string.
PeerManager needs to track peers' properties.
projects / quix0rs-apt-p2p.git / blobdiff