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| -rw-r--r-- | Documentation/networking/l2tp.rst | 37 |
1 files changed, 14 insertions, 23 deletions
diff --git a/Documentation/networking/l2tp.rst b/Documentation/networking/l2tp.rst index 693ea0e3ec26..498b382d25a0 100644 --- a/Documentation/networking/l2tp.rst +++ b/Documentation/networking/l2tp.rst @@ -455,31 +455,16 @@ l2tp help`` for more information. Debugging --------- -The L2TP subsystem offers a debug scheme where kernel trace messages -may be optionally enabled per tunnel and per session. Care is needed -when debugging a live system since the messages are not rate-limited -and a busy system could be swamped. Userspace uses setsockopt on the -PPPoX socket to set a debug mask, or ``L2TP_ATTR_DEBUG`` in netlink -Create and Modify commands. +The L2TP subsystem offers a range of debugging interfaces through the +debugfs filesystem. -The following debug mask bits are defined:- - -================ ============================== -L2TP_MSG_DEBUG verbose debug (if compiled in) -L2TP_MSG_CONTROL userspace - kernel interface -L2TP_MSG_SEQ sequence numbers handling -L2TP_MSG_DATA data packets -================ ============================== - -Sessions inherit default debug flags from the parent tunnel. - -If enabled, files under a l2tp debugfs directory can be used to dump -kernel state about L2TP tunnels and sessions. To access it, the -debugfs filesystem must first be mounted:: +To access these interfaces, the debugfs filesystem must first be mounted:: # mount -t debugfs debugfs /debug -Files under the l2tp directory can then be accessed:: +Files under the l2tp directory can then be accessed, providing a summary +of the current population of tunnel and session contexts existing in the +kernel:: # cat /debug/l2tp/tunnels @@ -488,8 +473,14 @@ state information because the file format is subject to change. It is implemented to provide extra debug information to help diagnose problems. Applications should instead use the netlink API. -/proc/net/pppol2tp is also provided for backwards compatibility with -the original pppol2tp code. It lists information about L2TPv2 +In addition the L2TP subsystem implements tracepoints using the standard +kernel event tracing API. The available L2TP events can be reviewed as +follows:: + + # find /debug/tracing/events/l2tp + +Finally, /proc/net/pppol2tp is also provided for backwards compatibility +with the original pppol2tp code. It lists information about L2TPv2 tunnels and sessions only. Its use is discouraged. Internal Implementation |