X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=doc%2Fsp.texi;h=41ebf45121da6e1284563dad454bbe3ad16a7ff8;hb=7edc3ed722c8d36e4a99b1cf45f209a973165a37;hp=b111988367312de51809402c087693661fd18eaa;hpb=4a4c1be88baf3fa5426bc1c9c96e104643155fca;p=nncp.git diff --git a/doc/sp.texi b/doc/sp.texi index b111988..41ebf45 100644 --- a/doc/sp.texi +++ b/doc/sp.texi @@ -1,13 +1,13 @@ @node Sync -@unnumbered Sync protocol +@unnumbered Synchronization protocol -So-called sync protocol (SP) is used in current TCP daemon's +So-called synchronization protocol (SP) is used in current TCP daemon's implementation. It is used for synchronizing @ref{Spool, spool} directory contents between two nodes. It is aimed to be very simple and effective. It uses reliable transport like TCP connections. It must be effective both on single-duplex and -full-duplex links: for example satellites have very high throughput and +full-duplex links: for example satellites have very high throughput but high-delay links, so acknowledging of each received packet, like @url{https://en.wikipedia.org/wiki/XMODEM, XMODEM} does, causes unacceptable performance degradation. @@ -15,7 +15,7 @@ unacceptable performance degradation. SP works on top of @url{http://noiseprotocol.org/noise.html#interactive-patterns, @code{Noise_IK_25519_ChaChaPoly_BLAKE2b}} protocol. Each Noise packet -are sent inside XDR envelope: +is sent inside an @url{https://tools.ietf.org/html/rfc4506, XDR} envelope: @verbatim +-----------------+ @@ -24,49 +24,54 @@ are sent inside XDR envelope: @end verbatim @multitable @columnfractions 0.2 0.3 0.5 -@headitem @tab XDR type @tab Value +@headitem @tab XDR type @tab Value @item Magic number @tab 8-byte, fixed length opaque data @tab - @code{NNCPS0x10x00x00} + @verb{|N N C P S 0x00 0x00 0x01|} @item Payload @tab variable length opaque data @tab Noise packet itself @end multitable -Peers static keys are specified as @ref{Configuration, @code{noisepub}} +Peers static keys are specified as @ref{Configuration, @emph{noisepub}} configuration entry. -Payload inside Noise packets has maximum size of @code{65 KiB - 256 B = +Payload inside Noise packets has maximum size of @emph{64 KiB - 256 B = 65280 B}. It is sent immediately in the first message by each side. The very first payload (that is carried inside handshake messages) is always -padded to the maximum size with @code{HALT} packets (read below), for -hiding actual number of @code{INFO} packets (number of files available +padded to the maximum size with @emph{HALT} packets (read below), for +hiding actual number of @emph{INFO} packets (number of files available for transmission). -Each SP payload is a concatenation of various SP packets. Each packet -has XDR-encoded header and then corresponding XDR-encoded body. Header -is just an unsigned integer telling what body structure follows. +Each SP payload is a concatenation of SP packets. Each packet has +XDR-encoded header and then corresponding XDR-encoded body. Header is +just an unsigned integer telling what body structure follows. -@table @code +@table @emph @item HALT Stop file transmission, empty sending queue on the remote side. - Actually @code{HALT} packet does not have any body, only the header + Actually @emph{HALT} packet does not have any body, only the header with the type. It is also used in the first payload for padding to the maximum size. +@verbatim ++------+ +| HALT | ++------+ +@end verbatim @item INFO Information about the file we have for transmission. @verbatim -+--------------------+ -| NICE | SIZE | HASH | -+--------------------+ ++------+--------------------+ +| INFO | NICE | SIZE | HASH | ++------+--------------------+ @end verbatim @multitable @columnfractions 0.2 0.3 0.5 - @headitem @tab XDR type @tab Value + @headitem @tab XDR type @tab Value @item Niceness @tab unsigned integer @tab - 1-255, file niceness level, its priority + 1-255, file niceness level @item Size @tab unsigned hyper integer @tab File size @@ -79,12 +84,12 @@ is just an unsigned integer telling what body structure follows. File transmission request. Ask remote side to queue the file for transmission. @verbatim -+---------------+ -| HASH | OFFSET | -+---------------+ ++------+---------------+ +| FREQ | HASH | OFFSET | ++------+---------------+ @end verbatim @multitable @columnfractions 0.2 0.3 0.5 - @headitem @tab XDR type @tab Value + @headitem @tab XDR type @tab Value @item Hash @tab 32-byte, fixed length opaque data @tab Unique file identifier, its checksum @@ -96,12 +101,12 @@ is just an unsigned integer telling what body structure follows. @item FILE Chunk of file. @verbatim -+-------------------------+ -| HASH | OFFSET | PAYLOAD | -+-------------------------+ ++------+-------------------------+ +| FILE | HASH | OFFSET | PAYLOAD | ++------+-------------------------+ @end verbatim @multitable @columnfractions 0.2 0.3 0.5 - @headitem @tab XDR type @tab Value + @headitem @tab XDR type @tab Value @item Hash @tab 32-byte, fixed length opaque data @tab Unique file identifier, its checksum @@ -116,15 +121,77 @@ is just an unsigned integer telling what body structure follows. @item DONE Signal remote side that we have successfully downloaded the file. @verbatim -+------+ -| HASH | -+------+ ++------+------+ +| DONE | HASH | ++------+------+ @end verbatim @multitable @columnfractions 0.2 0.3 0.5 - @headitem @tab XDR type @tab Value + @headitem @tab XDR type @tab Value @item Hash @tab 32-byte, fixed length opaque data @tab Unique file identifier, its checksum @end multitable @end table + +Typical peer's behaviour is following: + +@verbatiminclude sp.utxt + +@enumerate +@item Perform @emph{Noise-IK} handshake: + + @table @strong + @item Initiator + Collects all @emph{tx}-related files information and prepares + payload filled with @emph{INFO}s for including in the @strong{first} + handshake message. + @item Responder + After receiving the first handshake message, it gains remote + identity knowledge and similarly prepares the payload for including + in the @strong{second} handshake message. + @end table + + All payloads are padded to maximal message size with @emph{HALT}s. + +@item If queued @emph{INFO}s are not sent completely in handshake +payloads, then send all of remaining in the transport stage. + +@item When @emph{INFO} packet received: + + @itemize + @item Check that it has an acceptable niceness level. + Ignore it if it is too nice. + @item If already downloaded file exists, then queue @emph{DONE} + sending. + @item If @file{.seen} exists, then queue @emph{DONE} sending. + @item If @file{.part} exists, then queue @emph{FREQ} sending with + corresponding offset. + @end itemize + +@item When @emph{FREQ} packet received, append it to current sending +queue. Sending queue contains files with offsets that are needed to be +sent. + +@item While sending queue is not empty, send @emph{FILE} packets. +@emph{FREQ} could contain offset equal to size -- anyway sent +@emph{FILE} packet with an empty payload. @emph{FILE} sending is +performed only if no other outgoing packets are queued: @emph{INFO}s +have higher priority. + +@item When @emph{FILE} packet received, check if it is completely +downloaded (comparing to @emph{INFO}'s packet size information). If so, +then run background integrity checker on it. If check succeeds, then +delete @file{.part} suffix from file's name and send @emph{DONE} packet. + +@item When @emph{DONE} packet received, delete corresponding file. +@item When @emph{HALT} packet received, empty file sending queue. + +@item Each second, node checks: are there any new @emph{tx} packets +appeared and queues corresponding @emph{INFO} packets. + +@item If no packets are sent and received during @ref{CfgOnlineDeadline, +onlinedeadline} duration, then close the connection. There is no +explicit indication that session is over. + +@end enumerate