<!-- 
RSS generated by JIRA (9.12.2#9120002-sha1:301bf498dd45d800842af0b84230f1bb58606c13) at Sun Jan 12 11:52:20 UTC 2025

It is possible to restrict the fields that are returned in this document by specifying the 'field' parameter in your request.
For example, to request only the issue key and summary append 'field=key&field=summary' to the URL of your request.
-->
<rss version="0.92" >
<channel>
    <title>Mojang Studios Jira</title>
    <link>https://bugs.mojang.com</link>
    <description>This file is an XML representation of an issue</description>
    <language>en</language>    <build-info>
        <version>9.12.2</version>
        <build-number>9120002</build-number>
        <build-date>10-01-2024</build-date>
    </build-info>


<item>
            <title>[MC-823] Packets generated by third parties can cause heavy lag</title>
                <link>https://bugs.mojang.com/browse/MC-823</link>
                <project id="10400" key="MC">Minecraft: Java Edition</project>
                    <description>&lt;p&gt;Basically, certain poorly designed third party clients can cause heavy lag in multiplayer.&lt;/p&gt;

&lt;p&gt;Minecraft 1.3.1 and prior did not handle this very well at all.  Once a third party client did this, the server would go unresponsive and eventually crash.  But in 1.4, the CPU goes into very high utilization and recovers, usually within two minutes.&lt;/p&gt;

&lt;p&gt;During the recovery time, there is very heavy lag noticed by all the players still connected.&lt;/p&gt;

&lt;p&gt;So a lot of progress has been made to improve the situation since 1.3.1.  I&apos;m sure it&apos;s not a trivial task to make it even better, but this lag is highly disruptive.  Of course, adding a whitelist would mitigate it greatly, some servers opt to go without a whitelist.&lt;/p&gt;

&lt;p&gt;Here is an example from the server log of the kind of activity that causes this situation.&lt;/p&gt;

&lt;div class=&quot;preformatted panel&quot; style=&quot;border-width: 1px;&quot;&gt;&lt;div class=&quot;preformattedContent panelContent&quot;&gt;
&lt;pre&gt;2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [WARNING] KARLOX_11 was kicked for floating too long!
2012-10-26 17:08:12 [INFO] KARLOX_11 lost connection: disconnect.endOfStream&lt;/pre&gt;
&lt;/div&gt;&lt;/div&gt;</description>
                <environment>- Processor: 2 GHz Intel Core i7&lt;br/&gt;
- System Memory: 8 GB 1333 MHz DDR3&lt;br/&gt;
- Operating System: Mac OS X (x86_64) version 10.8.1&lt;br/&gt;
- Java Version: 1.7.0_07, Oracle Corporation&lt;br/&gt;
- Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation&lt;br/&gt;
- Memory: 918602576 bytes (876 MB) / 3221225472 bytes (3072 MB) up to 3221225472 bytes (3072 MB)&lt;br/&gt;
- JVM Flags: 5 total; -Xmx3G -Xms3G -Xloggc:server_gc.log -XX:+UseG1GC -XX:+DisableExplicitGC</environment>
        <key id="12103">MC-823</key>
            <summary>Packets generated by third parties can cause heavy lag</summary>
                <type id="1" iconUrl="https://bugs.mojang.com/secure/viewavatar?size=xsmall&amp;avatarId=18903&amp;avatarType=issuetype">Bug</type>
                                    <status id="5" iconUrl="https://bugs.mojang.com/images/icons/statuses/resolved.png" description="A resolution has been taken, and it is awaiting verification by reporter. From here issues are either reopened, or are closed.">Resolved</status>
                    <statusCategory id="3" key="done" colorName="success"/>
                                    <resolution id="3">Duplicate</resolution>
                                        <assignee username="-1">Unassigned</assignee>
                                    <reporter username="inertia">Anthony Martin</reporter>
                        <labels>
                            <label>multiplayer</label>
                            <label>protocol</label>
                            <label>server</label>
                    </labels>
                <created>Sat, 27 Oct 2012 02:42:09 +0200</created>
                <updated>Tue, 26 Nov 2013 19:21:17 +0100</updated>
                            <resolved>Tue, 26 Nov 2013 19:21:17 +0100</resolved>
                                    <version>Minecraft 1.4.1</version>
                    <version>Minecraft 1.4.5</version>
                    <version>Minecraft 1.5</version>
                                                                        <votes>7</votes>
                                    <watches>3</watches>
                                                                            <comments>
                            <comment id="106328" author="cubethethird" created="Thu, 26 Sep 2013 04:18:33 +0200"  >&lt;p&gt;Is this still a concern in the &lt;em&gt;current Minecraft version&lt;/em&gt; &lt;b&gt;1.6.4&lt;/b&gt; / Launcher version &lt;b&gt;1.2.5&lt;/b&gt; ? If so, please &lt;em&gt;update the affected versions&lt;/em&gt; in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.&lt;/p&gt;</comment>
                            <comment id="53725" author="inertia" created="Fri, 15 Mar 2013 21:59:56 +0100"  >&lt;p&gt;Not sure if it&apos;s related, but right after someone got kicked for flying, the server wouldn&apos;t take a /stop command.  After ^C, it finally stopped, then spit out a bunch of ConcurrentModification exceptions on the console.  I couldn&apos;t capture them in time to include them here.  They were not logged, must displayed on the console.&lt;/p&gt;</comment>
                            <comment id="53723" author="inertia" created="Fri, 15 Mar 2013 21:53:50 +0100"  >&lt;p&gt;Yes, in 1.5 as well as the snapshot (13w11a), the server seems even more susceptible to this problem.&lt;/p&gt;</comment>
                            <comment id="53133" author="bljat" created="Thu, 14 Mar 2013 19:01:28 +0100"  >&lt;p&gt;Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.&lt;/p&gt;</comment>
                            <comment id="26058" author="kumasasa" created="Sat, 1 Dec 2012 10:40:31 +0100"  >&lt;p&gt;Ok, thanks for the update.&lt;/p&gt;</comment>
                            <comment id="26057" author="inertia" created="Sat, 1 Dec 2012 10:37:31 +0100"  >&lt;p&gt;This is still very much a concern in 1.4.5.  Lag generated by these players is very disruptive.  I believe the players who generate these packets are using a combination of both fly and speed hacks.  Many players can &quot;tune&quot; their clients to avoid getting kicked.  But others intentionally try to generate packets that the server can&apos;t handle specifically to create a denial of service attack.&lt;/p&gt;</comment>
                            <comment id="26050" author="kumasasa" created="Sat, 1 Dec 2012 09:25:32 +0100"  >&lt;p&gt;Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.&lt;/p&gt;</comment>
                            <comment id="15064" author="inertia" created="Mon, 29 Oct 2012 17:25:18 +0100"  >&lt;p&gt;In another incident, a player claimed:&lt;/p&gt;

&lt;div class=&quot;preformatted panel&quot; style=&quot;border-width: 1px;&quot;&gt;&lt;div class=&quot;preformattedContent panelContent&quot;&gt;
&lt;pre&gt;2012-10-29 09:01:37 [INFO] &amp;lt;##REDACTED##&amp;gt; ok i used fly set 15000 now im at 3048343 and z is 42568
2012-10-29 09:01:38 [INFO] &amp;lt;##REDACTED##&amp;gt; :D&lt;/pre&gt;
&lt;/div&gt;&lt;/div&gt;

&lt;p&gt;Shortly after that, the server went unresponsive.  Apparently his third party client could overpower the server this way.  I checked the region files, and region r.5953.83.mca was never generated (thankfully).&lt;/p&gt;</comment>
                    </comments>
                <issuelinks>
                            <issuelinktype id="10102">
                    <name>Duplicate</name>
                                            <outwardlinks description="duplicates">
                                        <issuelink>
            <issuekey id="11528">MC-271</issuekey>
        </issuelink>
                            </outwardlinks>
                                                                <inwardlinks description="is duplicated by">
                                        <issuelink>
            <issuekey id="12261">MC-964</issuekey>
        </issuelink>
                            </inwardlinks>
                                    </issuelinktype>
                    </issuelinks>
                <attachments>
                    </attachments>
                <subtasks>
                    </subtasks>
                <customfields>
                                                                                                                                                                <customfield id="customfield_10701" key="com.atlassian.jira.plugin.system.customfieldtypes:datetime">
                        <customfieldname>CHK</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>Sat, 1 Dec 2012 10:40:00 +0100</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                            <customfield id="customfield_10500" key="com.atlassian.jira.plugin.system.customfieldtypes:radiobuttons">
                        <customfieldname>Confirmation Status</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="10300"><![CDATA[Unconfirmed]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                        <customfield id="customfield_11700" key="com.atlassian.jira.plugins.jira-development-integration-plugin:devsummary">
                        <customfieldname>Development</customfieldname>
                        <customfieldvalues>
                            
                        </customfieldvalues>
                    </customfield>
                                                                                                                        <customfield id="customfield_10501" key="com.atlassian.jira.plugin.system.customfieldtypes:radiobuttons">
                        <customfieldname>Game Mode</customfieldname>
                        <customfieldvalues>
                                <customfieldvalue key="10304"><![CDATA[Survival]]></customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                            <customfield id="customfield_11100" key="com.atlassian.jira.plugin.system.customfieldtypes:float">
                        <customfieldname>Linked</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>1.0</customfieldvalue>
                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                <customfield id="customfield_11600" key="com.pyxis.greenhopper.jira:gh-lexo-rank">
                        <customfieldname>Rank</customfieldname>
                        <customfieldvalues>
                            <customfieldvalue>0|i0mp7z:</customfieldvalue>

                        </customfieldvalues>
                    </customfield>
                                                                                                                                                                                                                                                                                                                                                                                    </customfields>
    </item>
</channel>
</rss>