unrealircd/doc/RELEASE-NOTES.md

UnrealIRCd 5.0.3.1 Release Notes

UnrealIRCd 5.0.3.1

This fixes a crash issue after REHASH in 5.0.3.

UnrealIRCd 5.0.3

Fixes:

• Fix serious flood issue in labeled-response implementation.
• An IRCOp SQUIT'ing a far remote server may cause a broken link topology
• In channels that are +D (delayed join), PARTs were not shown correctly to channel operators.

Enhancements:

• A new HISTORY command for history playback (HISTORY #channel number-of-lines) which allows you to fetch more lines than the on-join history playback. Of course, taking into account the set limits in the +H channel mode. This command is one of the two interfaces to Channel history.
• Two new message tags, unrealircd.org/userip and unrealircd.org/userhost which communicate the user@ip and real user@host to IRCOps.

Changes:

• Drop the draft/ prefix now that the IRCv3 labeled-response specification is out of draft.
• The operclass permission immune:target-limit is now called immune:max-concurrent-conversations, since it bypasses set::anti-flood::max-concurrent-conversations. For 99% of the users this change is not important, but it may be if you use highly customized operclass blocks

Are you upgrading from UnrealIRCd 4.x to UnrealIRCd 5? If so, then check out the UnrealIRCd 5 release notes further down. At the very least, check out Upgrading from 4.x.

UnrealIRCd 5.0.2

Fixes:

• Halfop users are not synced correctly, resulting in missing users across links.
• Channel history used incorrect time internally, resulting in messages expiring too soon. The syntax is now really /MODE #chan +H lines:time-in-minutes. To make clear that the time is in minutes, an 'm' will be added automatically by the server (eg +H 15:1440m).
• Documentation: to exempt someone from gline via /ELINE you have to use type 'G', not 'g'. Similarly, to exempt from spamfilter, use type 'F' and not 'f'.
• Exempting IPs from throttling via except throttle was not working.
• Unable to customize set::tls::outdated-protocols and set::tls::outdated-ciphers.
• Specifying multiple channels did not work in set::auto-join, set::oper-auto-join and tld::channel.

Enhancements:

• Extended server bans in *LINE and /ELINE allow you to ban or exempt users on criteria other than host/IP. These use a similar syntax to extended bans. Currently supported are ~a, ~S and ~r. Examples:
  • /ELINE ~a:TrustedAccount kG 0 This user can bypass kline/gline when using SASL
  • /ELINE ~S:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef kGF 0 Trusted user with this certificate fingerprint
  • /GLINE ~r:*some*stupid*real*name*
  • These can also be used in the configuration file, eg: except ban { mask ~S:11223344etc; type all; };
• New options that may not be used much, but can be useful on specific networks:
  • The IRCd may add automatic bans, for example due to a blacklist hit, a spamfilter hit, or because of antirandom or antimixedutf8. The new option set::automatic-ban-target specifies on what the ban should be placed. The default is ip. Other options are: userip, host, userhost, account, certfp.
  • Similarly, an oper may type /GLINE nickname. The new option set::manual-ban-target specifies on what the ban should be placed. By default this is host (fallback to ip).
• New options to exempt webirc users: set::connthrottle::webirc-bypass, set::restrict-commands::name-of-command::exempt-webirc.

UnrealIRCd 5.0.1

Fixes:

• IRCd may hang in rare circumstances
• Windows: fix repeated "ERROR renaming 'data/reputation.db.tmp'" warnings
• Antirandom and blacklist did not deal properly with 'warn' actions
• Authprompt did not always work properly
• Line numbers were incorrect in config file warnings/errors when using @if or @define

Enhancements:

• New /ELINE exception type 'm' to bypass allow::maxperip. Or in the configuration file: except ban { mask 203.0.113.0/24; type maxperip; };
• IRCOps can override MLOCK restrictions when services are down, if they have the channel:override:mlock operclass permission, such as opers which use the operclass 'netadmin-with-override'.

Other:

• Gottem and k4be have uploaded their 3rd party modules to unrealircd-contrib so *NIX users can now easily install them using the new Module manager

UnrealIRCd 5

After more than 6 months of hard work, UnrealIRCd 5 is now our new "stable" branch. In particular I would like to thank Gottem and 'i' for their source code contributions and PeGaSuS and westor for testing releases.

When we transitioned from 3.2.x to 4.0.0 there were 175,000 lines of source code added/removed during 3 years of development. This time it was 120,000 lines in only 6 months, a major effort!

If you are upgrading from 4.x to 5.x, then it would be wise to read Upgrading from 4.x. In any case, be sure to upgrade your services package first! (if you use any)

UnrealIRCd 5 is compatible with the following services:

• anope (version 2.0.7 or higher) - with the "unreal4" protocol module
• atheme (version 7.2.9 or higher) - with the "unreal4" protocol module

Summary

The most visible change to end-users is channel history. A lot of IRCv3 features were added. Various modules from Gottem have been integrated and enhanced. We now have a 3rd party module manager so you can install modules with 1 simple command. Channel settings of +P channels and *LINES are saved in a database and restored on startup (via 'channeldb' and 'tkldb' respectively). Channel mode +L has a slight change of meaning, the existing floodprot mode (+f) has a new type to prevent repeated messages and a new drop action. A few extended bans have been added as well (~f and ~p). IRCOps now have the ability to add ban exceptions via the /ELINE command. Advanced admins can use more dynamic configuration options where you can define variables and use them later in the configuration file. Finally, there have been speed improvements, we use better defaults and have added more countermeasures and options against spambots. Under the hood a significant amount of the source code was changed and cleaned up.

Read below for the full list of enhancements, changes and removals (and information for developers too).

Enhancements

• Support for IRCv3 server generated message tags, which allows us to communicate additional information in protocol messages such as in JOIN and PRIVMSG. Currently implemented and permitted message tags are:

  • account: communicate the services account that a user uses
  • msgid: assign an unique message id to each message
  • time: assign a time label to each message The last two are mainly for history playback.

• Support for IRCv3 echo-message, which helps clients, among other things, to see if the message you sent was altered in any way, eg: censored, stripped from color, etc.

• Support for IRCv3 draft/labeled-response-0.2, which helps clients to correlate commands and responses.

• Support for IRCv3 BATCH, needed for some other features.

• Recording and playback of channel history when channel mode +H is set. The syntax is: MODE #chan +H max-lines-to-record:max-time-to-record-in-minutes.

  For example: MODE #chan +H 50:1440 means the last 50 messages will be stored and no message will be stored longer than 1440 minutes (1 day).

  The channel history is then played back when joining such a channel, but with two things to keep in mind:

  1. The client must support the 'server-time' CAP ('time' message tag), otherwise history is not shown. Any modern IRC client supports this.
  2. Only a maximum of 15 lines are played back on-join by default

  The reason for the maximum 15 lines on-join playback is that this can be quite annoying if you rejoin repeatedly and as to not flood the users screen too much (unwanted). In the future we will support a mechanism for clients to "fetch" history - rather than sending it on-join - so they can fetch more than the 15 lines, up to the number of lines and time configured in the +H channel mode.

  You can configure the exact number of lines that are played back and all the limits that apply to +H via set::history::channel.

• For saving and retrieving history we currently have the following options:

  • history_backend_mem: channel history is stored in memory. This is very fast but also means history is lost on restart.
  • history_backend_null: don't store channel history at all. This can be useful to load on servers with no users on it, such as a hub server, where storing history is unnecessary.

  As you can see there is currently no 'disk' backend. However, in the future more options may be added. Also note that 3rd party modules can add history backends as well.

• Support for ban exceptions via the new /ELINE command. This allows you to add exceptions for regular bans (KLINE/GLINE/ZLINE/etc), but also for connection throttling and blacklist checking. For more information, just type /ELINE in your IRC client as an IRCOp.

• Websocket support now includes type 'text' in addition to 'binary', which should work with KiwiIRC's nextclient.

  Also, websockets are no longer active on all ports by default. You have to explicitly enable the websocket option in the listen block and also specify type text or binary, eg: listen { ip *; port 6667; options { websocket { type text; } } }

  Also note that websockets require nick names and channels to consist of UTF8 characters only, due to WebSocket being incompatible with non-UTF8

• There's now a Module manager which allows you to install and upgrade 3rd party modules in an easy way:

  • ./unrealircd module list - to list all available 3rd party modules
  • ./unrealircd module install third/something - to install the specified module.

• You can now test for configuration errors without actually starting the IRC server. This is ideal if you are upgrading UnrealIRCd to a newer version: simply run ./unrealircd configtest to make sure it passes the configuration test, and then you can safely restart the server for the upgrade (in this example case).

• Channel mode +L now kicks in for any rejected join, so not just for +l but also for +b, +i, +O, +z, +R and +k. If, for example, the channel is +L #insecure and also +z then, when an insecure user ties to join, they will be redirected to #insecure.

• New extended ban ~f to forward users to the specified channel if the ban matches. Example: MODE #chan +b ~f:#badisp:*!*@*.isp.org

• Channel mode +f now has a 'd' action: drop message. This will send an error message to the user and not show the message in the channel but otherwise do nothing (no kick or ban). For example: MODE #chan +f [5t#d]:15 will limit sending a maximum of 5 messages per 15 seconds per-user and drop any messages sent above that limit.

• Channel mode +f now has 'r' floodtype to prevent repeated lines. This will compare the current message to the last message and the one before that the user sent to the channel. If it's a repeat then the user can be kicked (the default action), the message can be dropped ('d') or the user can be banned ('b'). Example: MODE #chan +f [1r#d]:15 If you want to permit 1 repeated line but not 2 then use: +f [2r#d]:15

• New module tkldb (loaded by default): all *LINES and spamfilters are now saved across reboots. No need for services for that anymore.

• New module channeldb (loaded by default): saves and restores all channel settings including topic, modes, bans etc. of +P (persistent) channels.

• New module restrict-commands, which allows you to restrict any IRC command based on criteria such as "how long is this user connected", "is this user registered (has a services account)" etc. The example.conf now ships with configuration to disable LIST the first 60 seconds and disable INVITE the first 120 seconds. If you are having spambot problems then tweaking this configuration may be helpful to you.

• New option set::require-module, which allows you to require certain modules on other UnrealIRCd 5 servers, otherwise the link is rejected.

• New option set::min-nick-length to set a minimum nick length.

• New module rmtkl (loaded by default): this allows you to remove TKL's such as GLINEs easily via the /RMTKL command.

• The reputation and connthrottle modules are now loaded by default. Just as a reminder, what these do is classifying your users in "known users (known IP's)" and "unknown IP's" for IP's that have not been seen before (or only for a short amount of time). Then, when there is a connection flood, unknown/new IP addresses are throttled at 20 connections per minute, while known users are always allowed in.

• Add support for defines and conditional configuration via @define and @if. This is mostly for power users, in particular users who share the same configuration file across several servers.

• New extban ~p to hide the part/quit message in PART and QUIT. For example: MODE #chan +b ~p:*!*@*.nl

• You will now see a warning when a server is not responding even before they time out. How long to wait for a PONG reply upon PING can be changed via set::ping-warning and defaults to 15 seconds. If you see the warning frequently then your connection is flakey.

• Add new setting set::broadcast-channel-messages which defines when channel messages are sent across server links. The default setting is auto which is the correct setting for pretty much everyone.

• Add new option set::part-instead-of-quit-on-comment-change: when a QUIT message is changed due to channel restrictions, such as stripping color or censoring a word, we normally change the QUIT message. This has an effect on ALL channels, not just the one that imposed the restrictions. While we feel that is the best tradeoff, there is now also this new option (off by default) that will change the QUIT into a PART in such a case, so the other channels that do not have the restrictions (eg: are -S and -G) can still see the original QUIT message.

• New module webredir. Quite some people run their IRCd on port 443 or 80 so their users can avoid firewall restrictions in place. In such a case, with this module, you can now send a HTTP redirect in case some user enters your IRC server name in their browser. Eg https://irc.example.org/ can be made to redirect to https://www.example.org/

• We now protect against misbehaving SASL servers and will time out SASL sessions after set::sasl-timeout, which is 15 seconds by default.

Changed

• Channel mode +L can now be set by chanops (+o and higher) instead of only by +q (channel owner)

• Channel names must now be valid UTF8 by default. We actually have 3 possible settings of set::allowed-channelchars:

  • utf8: Channel must be valid UTF8, this is the new default
  • ascii: A very strict setting, for example in use at freenode, the channel name may not contain high ascii or UTF8
  • any: A very loose setting, which allows almost all characters in the channel name. This was the OLD default, up to and including UnrealIRCd 4. It is no longer recommended.

  For most networks this new default setting of utf8 will be fine, since by far most IRC clients use UTF8 for many years already. If you have a network that has a significant portion of chatters that are on old non-UTF8 clients that use a specific character set then you may want to use set { allowed-nickchars any; } Some Russian and Ukrainian networks are known to need this.

• The "except tkl" block is now called except ban. If no type is specified in an except ban { } block then we exempt the entry from kline, gline, zline, gzline and shun.

• We no longer use a blacklist for stats (set::oper-only-stats). We use a whitelist now instead: set::allow-user-starts. Most users can just remove their old set::oper-only-stats line, since the new default set::allow-user-starts setting is fine.

• Windows: we now require a 64-bit version, Windows 7 or later. The new program path is: C:\Program Files\UnrealIRCd 5 and the binaries have been moved to a new subdirectory: bin\

• Modules lost their m_ prefix, so for example m_map is now just map. Also the modules in cap/ are now directly in modules.

• More modules that were previously PERM (permanent) can now be unloaded and reloaded on the fly. This allows more "hotfixing" without restart in case of a bug and also more control for admins at runtime. Only <5 modules out of 173 are permanent now.

• User mode +T now blocks channel CTCPs as well.

• User mode +q (unkickable) could previously be set by any IRCOp. This has been changed to require the self:unkickablemode operclass permission. This is included in the *-with-override operclasses (eg: netadmin-with-operoverride).

• set::modes-on-join is now +nt by default.

• The authprompt module is now loaded by default. This means that if you do a soft kline on someone (eg: KLINE %*@*.badisp) then the user has a chance to authenticate to services, even without SASL, and bypass the ban if (s)he is authenticated.

• The WHOX module is now used by default. Previously it was optional. WHOX enhances the "WHO" output, providing additional information to IRC clients such as the services account that someone is using. It is also more universal than standard WHO. Unfortunately this also means the WHO syntax changed to something less logical.

• At many places the term SSL has been changed to SSL/TLS or TLS. Configuration items (eg: set::ssl to set::tls) have been renamed as well and so have directories (eg: conf/ssl to conf/tls). The old configuration names still work and currently does NOT raise any warning. Also, when upgrading an existing installation on *NIX, the conf/tls directory will be symlinked to conf/ssl as to not break any Let's Encrypt certificate scripts.

• It is now mandatory to have at least one open SSL/TLS port, otherwise UnrealIRCd will refuse to boot. Previously this was a warning.

• IRCOps now need to use SSL/TLS in order to oper up, as the set::plaintext-policy::oper default setting is now 'deny'. Similarly, set::outdated-tls-policy::oper is now also 'deny'. You can change this, if you want, but it is not recommended.

• set::outdated-tls-policy::server is now 'deny' as well, since all servers should use reasonable SSL/TLS protocols and ciphers.

• The default generated certificated has been changed from RSA 4096 bits to Elliptic Curve Cryptography "384r1". This provides the same amount of security but at higher speed. This only affects the default self- signed certificate. You can still use RSA certificates just fine.

• If you do use an RSA certificate, we now require it to be at least 2048 bits otherwise UnrealIRCd will refuse to boot.

• When matching allow { } blocks, we now always continue with the next block (if any) if the password did not match or no password was specified. In other words, allow::options::nopasscont is now the default and we behave as if there was a ::wrongpasscont too.

• All snomasks are now oper-only. Previously some were not, which was confusing and could lead to information leaks. Also removed weird set::snomask-on-connect accordingly.

• The IRCd now uses hash tables that are resilient against hash table attacks. Also, the hash tables have increased in size to speed things up when looking up nick names etc.

• Server options in VERSION (eg: Fhin6OoEMR3) are no longer shown to normal users. They don't mean much nowadays anyway.

• ./Config now asks fewer questions and configure runs faster since many unnecessary checks have been removed (compatibility with very old compilers / systems).

• We now default to system libs (eg: --with-system-pcre2 is assumed)

• Spamfilter should catch some more spam evasion techniques.

• All /DCCDENY and deny dcc { } parsing and checking is now moved to the 'dccdeny' module.

• Windows: If you choose to run UnrealIRCd as a service then it now runs under the low-privilege NetworkService account rather than the high-privilege LocalSystem account.

Minor issues fixed

• Specifying a custom OpenSSL/LibreSSL path should work now

Removed

• Support for old server protocols has been removed. This means UnrealIRCd 5.x cannot link to 3.2.x. It also means you need to use reasonably new services. Generally, if your services can link to 4.x then they should be able to link to 5.x as well. More information about this change and why it was done can be found here.
• Connecting with a server password will no longer send that password to NickServ. Use SASL instead!
• Extended ban ~R (registered nick): this was the old method to match registered users. Everyone should use ~a (services account) instead.
• The old TRE posix regex method has been removed because the TRE library is no longer maintained for over a decade and contains many bugs. (It was already deprecated in UnrealIRCd 4.2.3). Use type regex instead, which uses the modern PCRE2 regex engine.
• Timesync support has been removed. Use your OS time synchronization instead. (Note that Timesync was already disabled by default in 2018)
• Changing time offsets via TSCTL OFFSET and TSCTL SVSTIME are no longer supported. Use your OS time synchronization (NTP!). Adjustments via TSCTL are simply not accurate enough.
• The nopost module was removed since it no longer serves any useful purpose. UnrealIRCd already protects against these kind of attacks via ping cookies (set::ping-cookie, enabled by default).

Deprecated

• The set::official-channels block is now deprecated. This provided a mechanism to pre-configure channels that would have 0 members and would appear in /LIST with those settings, but once you joined all those settings would be gone. Rather confusing.

  Since UnrealIRCd 4.x we have permanent channels (+P) and since 5.x we store these permanent channels in a database so all settings are saved every few minutes and across restarts.

  Since permanent channels (+P) are much better, the official-channels support will be removed in a later version. There's no reason to use official-channels anymore.

Developers

• The module header is now as follows:

  ModuleHeader MOD_HEADER
    = {
          "nameofmodule",
          "5.0",
          "Some description", 
          "Name of Author",
          "unrealircd-5",
      };
  

  There's a new author field, the version must start with a digit, and also the name of the module must match the loadmodule name. So for example third/funmod must also be named third/funmod.

• The MOD_TEST, MOD_INIT, MOD_LOAD and MOD_UNLOAD functions no longer take a name argument. So: MOD_INIT(mymod) is now MOD_INIT()

• We now use our own BuildBot infrastructure, so Travis-CI and AppVeyor have been removed.

• We now use a new test framework.

• Auth_Check() now returns 1 for allow and 0 on deny (!!)

• New function new_message() which should be called when a new message is sent, or at least for all channel events. It adds (or inherits) message tags like 'account', 'msgid', 'time', etc.

• Many send functions now take an extra MessageTag *mtags parameter, including but not limited to: sendto_one() and sendto_server().

• Command functions (CMD_FUNC) have an extra MessageTag *mtags, on the other hand the cptr parameter has been removed.

• Command functions no longer return int but are void, the same is true for exit_client(). FLUSH_BUFFER has been removed too. All this is a consequence of removing this (limited) signaling of client exits. From now on, if you call exit_client() it will free a lot of the client data and exit the user (close socket, send [s]quit), but it will not free 'sptr' itself, so you can simply check if some upstream function killed the client by checking IsDead(sptr). This is highly recommended after running do_cmd() or calling other functions that could kill a client. In which case you should return rather than continue doing anything with sptr. Ultimately, in the main loop, the client will be freed (normally in less than 1 second).

• New single unified sendto_channel() and sendto_local_common_channels() functions that are used by all the channel commands.

• Numerics should now be sent using sendnumeric(). There's also a format string version sendnumericfmt() in case you need it, in which case you need to pass the numeric format string yourself. In such a case, don't forget the colon character, like ":%s", where needed.

• The parameters in several hooks have changed. Many now have an extra MessageTag *mtags parameter. Sometimes there are other changes as well, for example HOOKTYPE_CHANMSG now has 4 extra parameters.

• You can call do_cmd() with NULL mtags. Usually this is the correct way.

• If you used HOOKTYPE_PRE_USERMSG to block a message then you should now use HOOKTYPE_CAN_SEND_TO_USER. Similarly, the hook HOOKTYPE_CAN_SEND which deals with channels is now called HOOKTYPE_CAN_SEND_TO_CHANNEL. Some other remarks:

  • You CANNOT use HOOKTYPE_PRE_USERMSG anymore.
  • The hooks require you to set an error message if you return HOOK_DENY.
  • You should not send an error message yourself from these hooks. In other words: do not use sendnumeric(). This is done by the hook caller, based on the error message you return.
  • Thanks to this, all rejecting of user messages now use generic numeric 531 and all rejecting of channel messages use numeric 404. See also under Client protocol later in this document.

• If you use CommandOverrideAddEx() to specify a priority value (rare) then be aware that in 5.0.1 we now use the 4.0.x behavior again to match the same style of priorities in hooks: overrides with the lowest priority are run first.

• If you ever send a timestamp in a printf-like function, such as in sendto_server(), then be sure to use %lld and cast the timestamp to long long so that it is compatible with both *NIX and Windows. Example: sendnotice(sptr, "Timestamp is %lld", (long long)ts);

• EventAdd() changed the order of parameters and expects every_msec now which specifies the time in milliseconds rather than seconds. This allows for additional precision, or at least multiple calls per second. The minimum allowed every_msec value is 100 at this time. The prototype is now: EventAdd(Module *module, char *name, vFP event, void *data, long every_msec, int count);

• New HOOKTYPE_IS_HANDSHAKE_FINISHED. If a module returns 0 there, then the register_user() function will not be called and the user will not come online (yet). This is used by CAP and some other stuff. Can be useful if your module needs to "hold" a user in the registration phase.

• The function is_module_loaded() now takes a relative path like "usermodes/noctcp" because with just "ctcp" one could not see the difference between usermodes/noctcp and chanmodes/noctcp.

• CHFL_CHANPROT is now CHFL_CHANADMIN, is_chanprot() is now is_chanadmin()

• All hash tables now use SipHash, which is a hash function that is resilient against hash table attacks. If you, as a module dev, too use any hash tables anywhere (note: this is quite rare), then you are recommended to use our functions, see the functions siphash() and siphash_nocase() in src/hash.c.

• The random generator has been updated to use ChaCha (more modern).

• You can now save pointers and integers etc. across rehashes by using LoadPersistentPointer() and SavePersistentPointer(). For an example, see src/modules/chanmodes/floodprot.c how this can be used. Note that there can be no struct or type changes between rehashes.

• New ModData types: MODDATA_LOCALVAR and MODDA_GLOBALVAR. These are settings or things that are locally or globally identified by the variable name only and not attached to any user/channel.

• Various files have been renamed. As previously mentioned, the m_ prefix was dropped in src/modules/m_*.c. Similarly the s_ prefix was dropped in src/s_*.c since it no longer had meaning. Also some files have been deleted and integrated elsewhere or renamed to have a name that better reflects their true meaning. Related to this change is that all command functions are now called cmd_name rather than m_name.

• HOOKTYPE_CHECK_INIT and HOOKTYPE_PRE_LOCAL_CONNECT have their return value changed. You should now return HOOK_*, such as HOOK_DENY or HOOK_CONTINUE.

Server protocol

• UnrealIRCd 5 now assumes you support the following PROTOCTL options: NOQUIT EAUTH SID NICKv2 SJOIN SJ3 NICKIP TKLEXT2. If you fail to use SID or EAUTH then you will receive an error. For the other options, support is assumed, no warning or error is shown when you lack support. These are options that most, if not all, services support since UnrealIRCd 4.x so it shouldn't be a problem. More information here
• PROTOCTL MTAGS indicates that the server is capable of handling message tags and that the server can cope with 4K lines. (Note that the ordinary non-message-tag part is still limited to 512 bytes).
• Pseudo ID support in SASL was removed. We now use real UID's. This breaks services who rely on the old pseudo ID format.

Client protocol

• Support for message tags and other IRCv3 features. See the IRCv3 specifications for more details.
• When a message is blocked, for whatever reason, we now use a generic numeric response: :server 531 yourname targetname :reason for the block This replaces all the various NOTICEs, ERR_NOCTCP, ERR_NONONREG, etc. with just one single numeric. The only other numerics that you may still encounter when PM'ing are ERR_NOSUCHNICK, ERR_TOOMANYTARGETS and ERR_TARGETTOOFAST, which are generic errors to any command involving targets. And ERR_SERVICESDOWN. Note that channel messages already had a generic numeric for signaling blocked messages for a very long time, ERR_CANNOTSENDTOCHAN.
• The 271 response to the SILENCE command is now: :server 271 yournick listentry!*@* Previously the nick name appeared twice, which was a mistake.
• The 470 numeric, which is sent on /JOIN #channel redirect to #redirect now uses the following format: :server 470 yournick #channel #redirect :[Link] Cannot join channel...etc..
• Clients are recommended to implement and enable the server-time extension by default. When enabled, channel history is played back on-join (if any) when the channel has channel mode +H. Otherwise your users will not see channel history.