Server protocol:SJOIN command

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The SJOIN command is used to synchronize channel information between servers and for user joins.

Syntax

Syntax:

SJOIN timestamp channel [modes and parameters] :buffer

Where:

  • timestamp: creation time of the channel
  • channel: the channel name
  • modes and parameters: the modes, including parameters, eg: +lk 666 key. If the channel has no modes set then this parameter will not exist.
  • buffer: the sjoin buffer, explained further down

Creation time and behavior

Similar to MODE, different rules apply depending on how their_ts (the timestamp of the other server) compares to our_ts (the timestamp we have on record for the channel):

Timestamp Description of the situation What happens with the MODEs
their_ts == our_ts The channel has the same creation timestamp on both sides of the link. This means that the channel was not recreated. There's no risk of split riding or channel takeover, the channel is more or less in a "safe state". The IRC server will merge modes. So any modes set only on one side of the link will be added to the other side. This is true for channel modes (eg: +si), bans/exempts/invex (+beI) and privileges (+vhoaq).
their_ts < our_ts The other server holds the original channel and our channel was apparently (re)created later. They win. We will remove all modes on our side. So all channel modes (eg: -si), all lists (-beI) and privileges (-vhoaq).
their_ts > our_ts We hold the original channel and their channel was (re)created later. We are the winner. We simply ignore and do not set their modes. They will take care of removing their own modes.

So, the channel creation time decides what to do with the contents of the SJOIN command.

SJOIN buffer

Channel members

A simple SJOIN for three users in a channel that only has modes +nt set would look like this:

SJOIN 1548605089 #test +nt :One Two @Three

Upon receipt of such a message, the IRC server will send the following to it's locally connected users:

*** One joins #test
*** Two joins #test
*** Three joins #test
*** other.server sets modes: +o Three

In the SJOIN buffer each item is separated by spaces. The nick can be prefixed with the following characters to give the user certain channel privileges:

Character Description Mode
+ Voice +v
% Halfop +h
@ Op +o
~ Admin +a
* Owner +q

NOTE: As you can see the characters for +a and +q differ from the ones you see in NAMES as PREFIX on IRC. So take care not to mix them up!

Multiple characters can be combined if the user holds multiple privileges, eg +vo for user Ein will be communicated as +@Ein

Mode lists

The SJOIN command is also used to communicate +b (bans), +e (ban exempts) and +I (invite exceptions). For example:

SJOIN 1548605089 #test +nt :&this!is@a.ban "this!is@an.exempt 'this!is@an.invex

The first letter of each item tells the type of the list:

Character Description Mode
& Ban +b
" Ban exemption +e
' Invite exception +I
Extended information

For lists it is possible to prefix the buffer with additional information to communicate when and who set the +beI. This requires SJSBY to be enabled via PROTOCTL

Example without extended information:

SJOIN 1548605089 #test +nt :&this!is@a.ban

Example with extended information:

SJOIN 1548605089 #test +nt :<1548605202,UserOne>&this!is@a.ban

So, the <setat,setby> prefix is used to communicate this information. Being <1548605202,UserOne> in the example.

The server would still show this as:

*** some.server.net sets mode: +b this!is@a.ban

...but if the user queries the list at a later point by doing /MODE #channel b then it will show the user and time of the ban:

#test this!is@a.ban set by UserOne (Sun Jan 27 17:06:42 2019)
#test End of Channel Ban List