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Bram Matthys
b0dba4bede
and 7 for unknown-users (with max-bytes 5250 and 1500 respectively). This
allows pasting a short snippet of code, config file, text from a site, etc.
With multiline you have the guarantee that:
1) You will see the entire text with no delay between lines
2) You won't see another persons chat half-way through such a paste
3) For multiline supporting clients it is now clear that all the text
belongs to each other, which can make selecting/copying it easier.
This basically means short snippets/pastes like that can be completely on
IRC again. No need for a pastebin for it. Though, you may still need such
a service if you are pasting more lines.
Regarding the implementation in UnrealIRCd:
* Clients without multiline get individual fallback lines (concat lines
merged, blank lines skipped, as per spec). And we know that clients like
weechat - which does support multiline - also shows all lines and not
only a few plus snippet style "[.."]. That is another reason for only
allowing 15 lines by default and not something much more. Otherwise all
those clients would get a big wall of text, which just sucks.
* Spamfilter (also) runs on the full text of all lines together, so
splitting a phrase across lines does not evade spamfilter.
* Fakelag: a client can send the BATCH start+PRIVMSG (or NOTICE)+BATCH end
at full speed. We impose no fake lag there. Also, the multiline default
max-lines and max-bytes are lower than the example class::recvq of 8000,
so should be perfectly safe. If the entire BATCH is accepted then we
will impose fake-lag afterwards, with a cap of 15 seconds maximum.
If the BATCH is rejected, we impose half the fakelag plus 2sec.
* If the time between BATCH start and BATCH end is more than 15 seconds
then the BATCH is rejected (set::multiline::batch-timeout).
* The BATCH is atomic (either you see it all, or you see none of it):
* When the client sends it to server, it is buffered first.
* Only after the batch close the server indicates if it is accepted
or rejected. This has various reasons, two of them are: 1) The client
is going to send everything in one go anyway and not wait for a
response between each PRIVMSG, and 2) we can't do many checks in the
buffering stage and skip those after, that would cause a TOCTOU
problem (eg. a banned user still being able to speak).
* If any line gets rejected due to spamfilter or other case
(eg +c, +b ~text with block, etc etc), the entire batch is rejected
* Locally we deliver all or nothing (as said)
* S2S we buffer the batch as well, so if a server splits after having
received 10 lines out of 15, then clients will not see anything.
* We send max-lines and max-bytes, this is the hard upper limit.
* A multiline can still be limited more tight if:
* +f with 't' or 'm' restricts to fewer lines,
eg +f [5t]:15, which means max 5 lines per 15 seconds,
means the max accepted multiline is 5 for that channel.
* +F works the same, except that default +F normal does not
have a 't' at the moment and 'm' is very high (50) so
practically not limited by default.
* There will be a future +f flood subtype for some more control
TODO: we will send CAP NEW on unknown-users <-> known-users to
indicate the new max-lines value if you transition security groups
TODO: chat history does not yet include multiline batches.