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, 24 insertions, 25 deletions

diff --git a/net/sctp/transport.c b/net/sctp/transport.c
index 5d3c71bbd197..bdbbc3fd7c14 100644
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -176,7 +176,10 @@ static void sctp_transport_destroy_rcu(struct rcu_head *head)
  */
 static void sctp_transport_destroy(struct sctp_transport *transport)
 {
-	SCTP_ASSERT(transport->dead, "Transport is not dead", return);
+	if (unlikely(!transport->dead)) {
+		WARN(1, "Attempt to destroy undead transport %p!\n", transport);
+		return;
+	}
 
 	call_rcu(&transport->rcu, sctp_transport_destroy_rcu);
 
@@ -317,11 +320,9 @@ void sctp_transport_put(struct sctp_transport *transport)
 /* Update transport's RTO based on the newly calculated RTT. */
 void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
 {
-	/* Check for valid transport.  */
-	SCTP_ASSERT(tp, "NULL transport", return);
-
-	/* We should not be doing any RTO updates unless rto_pending is set.  */
-	SCTP_ASSERT(tp->rto_pending, "rto_pending not set", return);
+	if (unlikely(!tp->rto_pending))
+		/* We should not be doing any RTO updates unless rto_pending is set.  */
+		pr_debug("%s: rto_pending not set on transport %p!\n", __func__, tp);
 
 	if (tp->rttvar || tp->srtt) {
 		struct net *net = sock_net(tp->asoc->base.sk);
@@ -377,9 +378,8 @@ void sctp_transport_update_rto(struct sctp_transport *tp, __u32 rtt)
 	 */
 	tp->rto_pending = 0;
 
-	SCTP_DEBUG_PRINTK("%s: transport: %p, rtt: %d, srtt: %d "
-			  "rttvar: %d, rto: %ld\n", __func__,
-			  tp, rtt, tp->srtt, tp->rttvar, tp->rto);
+	pr_debug("%s: transport:%p, rtt:%d, srtt:%d rttvar:%d, rto:%ld\n",
+		 __func__, tp, rtt, tp->srtt, tp->rttvar, tp->rto);
 }
 
 /* This routine updates the transport's cwnd and partial_bytes_acked
@@ -433,12 +433,11 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
 			cwnd += pmtu;
 		else
 			cwnd += bytes_acked;
-		SCTP_DEBUG_PRINTK("%s: SLOW START: transport: %p, "
-				  "bytes_acked: %d, cwnd: %d, ssthresh: %d, "
-				  "flight_size: %d, pba: %d\n",
-				  __func__,
-				  transport, bytes_acked, cwnd,
-				  ssthresh, flight_size, pba);
+
+		pr_debug("%s: slow start: transport:%p, bytes_acked:%d, "
+			 "cwnd:%d, ssthresh:%d, flight_size:%d, pba:%d\n",
+			 __func__, transport, bytes_acked, cwnd, ssthresh,
+			 flight_size, pba);
 	} else {
 		/* RFC 2960 7.2.2 Whenever cwnd is greater than ssthresh,
 		 * upon each SACK arrival that advances the Cumulative TSN Ack
@@ -459,12 +458,12 @@ void sctp_transport_raise_cwnd(struct sctp_transport *transport,
 			cwnd += pmtu;
 			pba = ((cwnd < pba) ? (pba - cwnd) : 0);
 		}
-		SCTP_DEBUG_PRINTK("%s: CONGESTION AVOIDANCE: "
-				  "transport: %p, bytes_acked: %d, cwnd: %d, "
-				  "ssthresh: %d, flight_size: %d, pba: %d\n",
-				  __func__,
-				  transport, bytes_acked, cwnd,
-				  ssthresh, flight_size, pba);
+
+		pr_debug("%s: congestion avoidance: transport:%p, "
+			 "bytes_acked:%d, cwnd:%d, ssthresh:%d, "
+			 "flight_size:%d, pba:%d\n", __func__,
+			 transport, bytes_acked, cwnd, ssthresh,
+			 flight_size, pba);
 	}
 
 	transport->cwnd = cwnd;
@@ -558,10 +557,10 @@ void sctp_transport_lower_cwnd(struct sctp_transport *transport,
 	}
 
 	transport->partial_bytes_acked = 0;
-	SCTP_DEBUG_PRINTK("%s: transport: %p reason: %d cwnd: "
-			  "%d ssthresh: %d\n", __func__,
-			  transport, reason,
-			  transport->cwnd, transport->ssthresh);
+
+	pr_debug("%s: transport:%p, reason:%d, cwnd:%d, ssthresh:%d\n",
+		 __func__, transport, reason, transport->cwnd,
+		 transport->ssthresh);
 }
 
 /* Apply Max.Burst limit to the congestion window: