1 files changed, 31 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 8b72c88ba213..d0536b5a4e01 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -588,6 +588,37 @@ ip_local_port_range - 2 INTEGERS
         (i.e. by default) range 1024-4999 is enough to issue up to
         2000 connections per second to systems supporting timestamps.
 
+ip_local_reserved_ports - list of comma separated ranges
+        Specify the ports which are reserved for known third-party
+        applications. These ports will not be used by automatic port
+        assignments (e.g. when calling connect() or bind() with port
+        number 0). Explicit port allocation behavior is unchanged.
+
+        The format used for both input and output is a comma separated
+        list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
+        10). Writing to the file will clear all previously reserved
+        ports and update the current list with the one given in the
+        input.
+
+        Note that ip_local_port_range and ip_local_reserved_ports
+        settings are independent and both are considered by the kernel
+        when determining which ports are available for automatic port
+        assignments.
+
+        You can reserve ports which are not in the current
+        ip_local_port_range, e.g.:
+
+        $ cat /proc/sys/net/ipv4/ip_local_port_range
+        32000   61000
+        $ cat /proc/sys/net/ipv4/ip_local_reserved_ports
+        8080,9148
+
+        although this is redundant. However such a setting is useful
+        if later the port range is changed to a value that will
+        include the reserved ports.
+
+        Default: Empty
+
 ip_nonlocal_bind - BOOLEAN
         If set, allows processes to bind() to non-local IP addresses,
         which can be quite useful - but may break some applications.