l2tp: Add debugfs files for dumping l2tp debug info

The existing pppol2tp driver exports debug info to
/proc/net/pppol2tp. Rather than adding info to that file for the new
functionality added in this patch series, we add new files in debugfs,
leaving the old /proc file for backwards compatibility (L2TPv2 only).

Currently only one file is provided: l2tp/tunnels, which lists
internal debug info for all l2tp tunnels and sessions. More files may
be added later. The info is for debug and problem analysis only -
userspace apps should use netlink to obtain status about l2tp tunnels
and sessions.

Although debugfs does not support net namespaces, the tunnels and
sessions dumped in l2tp/tunnels are only those in the net namespace of
the process reading the file.

Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 0 deletions

diff --git a/net/l2tp/Kconfig b/net/l2tp/Kconfig
index a292270c0abe..4b1e71751e10 100644
--- a/net/l2tp/Kconfig
+++ b/net/l2tp/Kconfig
@@ -31,6 +31,19 @@ menuconfig L2TP
           If you don't need L2TP, say N. To compile all L2TP code as
           modules, choose M here.
 
+config L2TP_DEBUGFS
+        tristate "L2TP debugfs support"
+        depends on L2TP && DEBUG_FS
+        help
+          Support for l2tp directory in debugfs filesystem. This may be
+          used to dump internal state of the l2tp drivers for problem
+          analysis.
+
+          If unsure, say 'Y'.
+
+          To compile this driver as a module, choose M here. The module
+          will be called l2tp_debugfs.
+
 config L2TP_V3
         bool "L2TPv3 support (EXPERIMENTAL)"
         depends on EXPERIMENTAL && L2TP