man: document dynamic debug trick for Linux

This comes up occasionally, so it may be useful to mention its
possibility in the man page. At least the Arch Linux and Ubuntu kernels
support dynamic debugging, so this advise will at least help somebody.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/man/wg.8 b/src/man/wg.8
index 07b969491c5fe1c0fa221621870b032cc5adc702..27860c8905bc42c2a556c3ae4c6b9ce163159f86 100644 (file)
--- a/src/man/wg.8
+++ b/src/man/wg.8
@@ -212,6 +212,15 @@ are thus ignored.
 .br
     AllowedIPs = 10.10.10.230/32
 
+.SH DEBUGGING INFORMATION
+Sometimes it is useful to have information on the current runtime state of a tunnel. When using the Linux kernel module on a kernel that supports dynamic debugging, debugging information can be written into
+.BR dmesg (1)
+by running as root:
+
+\fB    # modprobe wireguard && echo module wireguard +p > /sys/kernel/debug/dynamic_debug/control\fP
+
+On userspace implementations, it is customary to set the \fILOG_LEVEL\fP environment variable to \fIdebug\fP.
+
 .SH ENVIRONMENT VARIABLES
 .TP
 .I WG_COLOR_MODE