net: sctp: rework debugging framework to use pr_debug and friends

We should get rid of all own SCTP debug printk macros and use the ones
that the kernel offers anyway instead. This makes the code more readable
and conform to the kernel code, and offers all the features of dynamic
debbuging that pr_debug() et al has, such as only turning on/off portions
of debug messages at runtime through debugfs. The runtime cost of having
CONFIG_DYNAMIC_DEBUG enabled, but none of the debug statements printing,
is negligible [1]. If kernel debugging is completly turned off, then these
statements will also compile into "empty" functions.

While we're at it, we also need to change the Kconfig option as it /now/
only refers to the ifdef'ed code portions in outqueue.c that enable further
debugging/tracing of SCTP transaction fields. Also, since SCTP_ASSERT code
was enabled with this Kconfig option and has now been removed, we
transform those code parts into WARNs resp. where appropriate BUG_ONs so
that those bugs can be more easily detected as probably not many people
have SCTP debugging permanently turned on.

To turn on all SCTP debugging, the following steps are needed:

 # mount -t debugfs none /sys/kernel/debug
 # echo -n 'module sctp +p' > /sys/kernel/debug/dynamic_debug/control

This can be done more fine-grained on a per file, per line basis and others
as described in [2].

 [1] https://www.kernel.org/doc/ols/2009/ols2009-pages-39-46.pdf
 [2] Documentation/dynamic-debug-howto.txt

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 5 deletions

diff --git a/net/sctp/Kconfig b/net/sctp/Kconfig
index cf48528..d80bf1a 100644
--- a/net/sctp/Kconfig
+++ b/net/sctp/Kconfig
@@ -30,7 +30,8 @@ menuconfig IP_SCTP
 	  homing at either or both ends of an association."
 
 	  To compile this protocol support as a module, choose M here: the
-	  module will be called sctp.
+	  module will be called sctp. Debug messages are handeled by the
+	  kernel's dynamic debugging framework.
 
 	  If in doubt, say N.
 
@@ -48,13 +49,14 @@ config NET_SCTPPROBE
         To compile this code as a module, choose M here: the
         module will be called sctp_probe.
 
-config SCTP_DBG_MSG
-	bool "SCTP: Debug messages"
+config SCTP_DBG_TSNS
+	bool "SCTP: Debug transactions"
 	help
-	  If you say Y, this will enable verbose debugging messages. 
+	  If you say Y, this will enable transaction debugging, visible
+	  from the kernel's dynamic debugging framework.
 
 	  If unsure, say N.  However, if you are running into problems, use 
-	  this option to gather detailed trace information
+	  this option to gather outqueue trace information.
 
 config SCTP_DBG_OBJCNT
 	bool "SCTP: Debug object counts"