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-rw-r--r--lib/ssh/doc/src/ssh.xml21
1 files changed, 17 insertions, 4 deletions
diff --git a/lib/ssh/doc/src/ssh.xml b/lib/ssh/doc/src/ssh.xml
index 7fbd70c87e..57aab09cc6 100644
--- a/lib/ssh/doc/src/ssh.xml
+++ b/lib/ssh/doc/src/ssh.xml
@@ -307,18 +307,31 @@
<tag><c><![CDATA[{negotiation_timeout, integer()}]]></c></tag>
<item>
- <p>Max time in milliseconds for the authentication negotiation. The default value is 2 minutes.
+ <p>Max time in milliseconds for the authentication negotiation. The default value is 2 minutes. If the client fails to login within this time, the connection is closed.
+ </p>
+ </item>
+
+ <tag><c><![CDATA[{max_sessions, pos_integer()}]]></c></tag>
+ <item>
+ <p>The maximum number of simultaneous sessions that are accepted at any time for this daemon. This includes sessions that are being authorized. So if set to <c>N</c>, and <c>N</c> clients have connected but not started the login process, the <c>N+1</c> connection attempt will be aborted. If <c>N</c> connections are authenticated and still logged in, no more loggins will be accepted until one of the existing ones log out.
+ </p>
+ <p>The counter is per listening port, so if two daemons are started, one with <c>{max_sessions,N}</c> and the other with <c>{max_sessions,M}</c> there will be in total <c>N+M</c> connections accepted for the whole ssh server.
+ </p>
+ <p>Note that if <c>parallel_login</c> is <c>false</c>, only one client at a time may be in the authentication phase.
+ </p>
+ <p>As default, the option is not set. This means that the number is not limited.
</p>
</item>
<tag><c><![CDATA[{parallel_login, boolean()}]]></c></tag>
<item>
- <p>If set to false (the default value), only one login is handled a time. If set to true, an unlimited logins will be allowed simultanously. Note that this affects only the connections with authentication in progress, not the already authenticated connections.
+ <p>If set to false (the default value), only one login is handled a time. If set to true, an unlimited number of login attempts will be allowed simultanously.
+ </p>
+ <p>If the <c>max_sessions</c> option is set to <c>N</c> and <c>parallel_login</c> is set to <c>true</c>, the max number of simultaneous login attempts at any time is limited to <c>N-K</c> where <c>K</c> is the number of authenticated connections present at this daemon.
</p>
<warning>
- <p>Do not enable parallel_logins without protecting the server by other means like a firewall. If set to true, there is no protection against dos attacs.</p>
+ <p>Do not enable <c>parallel_logins</c> without protecting the server by other means, for example the <c>max_sessions</c> option or a firewall configuration. If set to <c>true</c>, there is no protection against DOS attacks.</p>
</warning>
-
</item>
<tag><c><![CDATA[{key_cb, atom()}]]></c></tag>