X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=doc%2Fsp.texi;h=3944a752f630d5c53d1dd6bc9ef08f22e1994fb2;hb=09d14cc39cce6710af382e3a178d215be268a0d7;hp=75019c024cc7425262abaf7ab377b47b52f84840;hpb=953dbfc308ce51814274bfb0ffb1a42c1344c5e0;p=nncp.git

diff --git a/doc/sp.texi b/doc/sp.texi
index 75019c0..3944a75 100644
--- a/doc/sp.texi
+++ b/doc/sp.texi
@@ -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
 +-----------------+
@@ -24,46 +24,63 @@ 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 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 PING
+    Dummy packet only used for determining workability of the connection.
+
+@verbatim
++------+
+| PING |
++------+
+@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
@@ -78,13 +95,15 @@ just an unsigned integer telling what body structure follows.
 @item FREQ
     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
@@ -95,13 +114,15 @@ 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
@@ -115,16 +136,88 @@ 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.plantuml.txt
+
+@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/XXX} 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, insert it to current sending
+queue with niceness level sort: higher priority packets will be sent
+first. 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 Each minute, if no packets were sent, node sends @emph{PING}
+packet.
+
+@item If no non-PING packets are sent and received during
+@ref{CfgOnlineDeadline, onlinedeadline} duration, then close the
+connection. There is no explicit indication that session is over.
+
+@item If no packets are received during two minutes (two PING timeouts),
+then close the connection.
+
+@end enumerate