xdp-trafficgen: Document the 'probe' command

The 'probe' command was missing from the top-level help output, and the
man page. Let's add it to both.

Signed-off-by: Toke Høiland-Jørgensen <[email protected]>

Author: tohojo

xdp-trafficgen/README.org

@@ -28,6 +28,7 @@ Usage: xdp-trafficgen COMMAND [options]
 COMMAND can be one of:
        udp         - run in UDP mode
        tcp         - run in TCP mode
+       probe       - probe kernel support
 #+end_src
 
 Each command, and its options are explained below. Or use =xdp-trafficgen COMMAND
@@ -151,6 +152,39 @@ Display version information and exit.
 ** -h, --help
 Display a summary of the available options
 
+* The PROBE command
+The PROBE command probes the kernel to discover whether it supports the features
+needed to run xdp-trafficgen. This can be used to discover whether the running
+kernel is compatible with xdp-trafficgen, as well as to discover whether a
+particular interface supports sending packets generated by xdp-trafficgen.
+
+The syntax for the =probe= command is:
+
+=xdp-trafficgen probe [options]=
+
+After probing, xdp-trafficgen will print the results of the probing of the
+kernel, and (if an interface name is supplied), whether the interface supports
+sending packets generated by xdp-trafficgen. The exit code will be 0 if all
+probes succeed, and 1 otherwise.
+
+Note that the probing relies on the kernel XDP feature reporting, which was
+added after the XDP support itself. This means that with some older kernel
+versions, the probing may fail even though xdp-trafficgen would in fact be able
+to transmit packets.
+
+The supported options are:
+
+** -i, --ifname <ifname>
+Probe the supplied interface name, in addition to doing the general kernel probing.
+
+** -v, --verbose
+Enable verbose logging (-vv: more verbose).
+
+** --version
+Display version information and exit.
+
+** -h, --help
+Display a summary of the available options
 
 * BUGS
 

xdp-trafficgen/xdp-trafficgen.8

@@ -1,4 +1,4 @@
-.TH "xdp-trafficgen" "8" "JANUARY  9, 2025" "V1.5.5" "An XDP-based traffic generator"
+.TH "xdp-trafficgen" "8" "MAY 28, 2025" "V1.5.5" "An XDP-based traffic generator"
 .SH "NAME"
 XDP-trafficgen \- an XDP-based traffic generator
 .SH "SYNOPSIS"
@@ -23,6 +23,7 @@ The syntax for running xdp-trafficgen is:
 COMMAND can be one of:
        udp         - run in UDP mode
        tcp         - run in TCP mode
+       probe       - probe kernel support
 \fP
 .fi
 .RE
@@ -156,6 +157,45 @@ Display version information and exit.
 .SS "-h, --help"
 .PP
 Display a summary of the available options
+.SH "The PROBE command"
+.PP
+The PROBE command probes the kernel to discover whether it supports the features
+needed to run xdp-trafficgen. This can be used to discover whether the running
+kernel is compatible with xdp-trafficgen, as well as to discover whether a
+particular interface supports sending packets generated by xdp-trafficgen.
+
+.PP
+The syntax for the \fIprobe\fP command is:
+
+.PP
+\fIxdp\-trafficgen probe [options]\fP
+
+.PP
+After probing, xdp-trafficgen will print the results of the probing of the
+kernel, and (if an interface name is supplied), whether the interface supports
+sending packets generated by xdp-trafficgen. The exit code will be 0 if all
+probes succeed, and 1 otherwise.
+
+.PP
+Note that the probing relies on the kernel XDP feature reporting, which was
+added after the XDP support itself. This means that with some older kernel
+versions, the probing may fail even though xdp-trafficgen would in fact be able
+to transmit packets.
+
+.PP
+The supported options are:
+.SS "-i, --ifname <ifname>"
+.PP
+Probe the supplied interface name, in addition to doing the general kernel probing.
+.SS "-v, --verbose"
+.PP
+Enable verbose logging (-vv: more verbose).
+.SS "--version"
+.PP
+Display version information and exit.
+.SS "-h, --help"
+.PP
+Display a summary of the available options
 .SH "BUGS"
 .PP
 Please report any bugs on Github: \fIhttps://github.com/xdp-project/xdp-tools/issues\fP

xdp-trafficgen/xdp-trafficgen.c

@@ -1056,6 +1056,7 @@ int do_help(__unused const void *cfg, __unused const char *pin_root_path)
 		"COMMAND can be one of:\n"
 		"       udp         - run in UDP mode\n"
 		"       tcp         - run in TCP mode\n"
+		"       probe       - probe kernel support\n"
 		"       help        - show this help message\n"
 		"\n"
 		"Use 'xdp-trafficgen COMMAND --help' to see options for each command\n");