CFLAGS

Name

CFLAGS -- Display / Set Connection Control Flags for a Port.

Synopsis

CFLAGS <port> [flags]

Availability

Sysop-only.

Description

CFLAGS is a port configuration command which is used to display or change the connection control flags for a specified PORT. The primary purpose of these flags is to control whether or not AX25 level 2 uplinking and/or downlinking is allowed on the port.

A typical use may be to prevent users from uplinking and downlinking on APRS-only ports.

It also allows the sysop to control whether or not L3RTT frames are generated on inter-node links, and whether or not AX25 level 2 fragmentation is allowed on the port.

Options

If a single numeric argument is supplied, and it is a valid port number, the current CFLAGS setting for that port number is displayed.

If two numeric arguments are supplied, the first specifies a port number and the second specifies a new CFLAGS value for that port.

The [flags] argument is formed by adding together the decimal values of the desired options from this list:

	Bit Dec   Function
	---------------------------------------------------------
	 0   1  - Allow incoming connections (uplinks).
	 1   2  - Allow outgoing connections (downlinks).
	 2   4  - Applications may downlink unconditionally.
	 3   8  - Suppress L3RTT generation.
	 4  16  - Allow L2 fragmentation.

The default value is 3, i.e. unconditional use of the port.

Irrespective of the setting of CFLAGS, the Sysop can always downlink.

Bit 2 allows applications to downlink unconditionally, i.e. even if users are prevented from downlinking.

Bit 3 was provided to keep the Luddites happy, but its use is strongly deprecated. Setting this flag prevents L3RTT frames from being originated by the port if it is carrying an inter-node link. It will not prevent XRPi from trying to hold inter-node links open, as that is too much of a retrograde step! This bit is not set by default. Note that L3RTT may also be suppressed if a route's MAXTT is 65535.

Bit 4 allows AX25 layer 2 fragmentation if it is set. This is required if Forward Error Correction (FEC) is in use, to allow big L3 frames to be sent.

Examples

	CFLAGS=2  - Allow downlinking only
	CFLAGS=5  - Allow only sysops and apps to downlink.

Files

CFLAGS is also PORT configuration directive used in XROUTER.CFG.

See also

CFLAGS(7) -- Connection Control Flags
L2FRAG(9) -- AX25 Layer 2 Fragmentation.
L3RTT(9) -- Layer 3 Round Trip Time.
FEC(2) -- Forward Error Correction.
XROUTER.CFG(8) -- Main Configuration File.