file: /proc/sys/net/ipv4/cipso_rbm_structvalid
variable: net.ipv4.cipso_rbm_structvalid
Official reference

If set, do a very strict check of the CIPSO option when ip_options_compile() is called. If unset, relax the checks done during ip_options_compile(). Either way is “safe” as errors are caught else where in the CIPSO processing code but setting this to 0 (False) should result in less work (i.e. it should be faster) but could cause problems with other implementations that require strict checking. Default: 0

ip_local_port_range - 2 INTEGERS Defines the local port range that is used by TCP and UDP to choose the local port. The first number is the first, the second the last local port number. If possible, it is better these numbers have different parity. (one even and one odd values) The default values are 32768 and 60999 respectively.

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 60999 $ 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