Convert net_msg_warn, NETDEBUG, & LIMIT_NETDEBUG?

net_msg_warn is a sysctl used to control the printk of a bundle of mostly ipv4/ipv6 logging messages.

Does anyone use it?

NETDEBUG is used 4 times, 2 of which seem senseless as they are allocation failures messages after an alloc_skb. These already get stack dumps.

The other NETDEBUG uses are ESP crypto descriptions.

LIMIT_NETDEBUG is used a lot more.

include/net/sock.h:#define LIMIT_NETDEBUG(fmt, args...) \
include/net/sock.h- do { if (net_msg_warn && net_ratelimit()) printk(fmt,##args); } while(0)

Most of the LIMIT_NETDEBUG uses are emitted at KERN_DEBUG.

Here is the count of each type of use:
31 KERN_DEBUG
2 KERN_ERR
3 KERN_INFO
11 KERN_WARNING

Should those KERN_DEBUG uses be converted to net_dbg_ratelimited so that these uses could be controlled via dynamic_debug instead of the net_msg_warn sysctl?

net/dccp/ uses LIMIT_NETDEBUG via DCCP_WARN to control another 38 KERN_WARNING messages.

The others LIMIT_NETDEBUG uses could be converted to net_<level>_ratelimited if appropriate.

From: Joe Perches <[email protected]>
Date: Tue, 04 Nov 2014 12:46:40 -0800

...

...

I will respond to this by saying that, generally speaking, I'd rather we move away from local debugging facility and controls and towards the generic ones.

Definitely kill the allocation failure debug stuff, that's obviously superfluous and bogus.

It may be the case that we're stuck with the net_msg_warn sysctl for the stuff that isn't obviously extraneous and removable like the allocation failure cases.

Why don't we work on these one at a time and see what's left after all the adjustments/deletions?

Thanks.

These messages aren't useful as there's a generic dump_stack() on OOM.

Neaten the comment and if test above the OOM by separating the assign in if into an allocation then if test.

---
 net/ipv4/ip_output.c  |  8 +++-----
 net/ipv6/ip6_output.c | 10 ++++------
 2 files changed, 7 insertions(+), 11 deletions(-)

index bc6471d..4a929ad 100644
@@ -662,12 +662,10 @@ slow_path:
 		if (len < left)	{
 			len &= ~7;
 		}
-		/*
-		 *	Allocate buffer.
-		 */
 
-		if ((skb2 = alloc_skb(len+hlen+ll_rs, GFP_ATOMIC)) == NULL) {
-			NETDEBUG(KERN_INFO "IP: frag: no memory for new fragment!\n");
+		/* Allocate buffer */
+		skb2 = alloc_skb(len + hlen + ll_rs, GFP_ATOMIC);
+		if (!skb2) {
 			err = -ENOMEM;
 			goto fail;
 		}

index 8e950c2..916d2a1 100644
@@ -747,13 +747,11 @@ slow_path:
 		if (len < left)	{
 			len &= ~7;
 		}
-		/*
-		 *	Allocate buffer.
-		 */
 
-		if ((frag = alloc_skb(len + hlen + sizeof(struct frag_hdr) +
-				      hroom + troom, GFP_ATOMIC)) == NULL) {
-			NETDEBUG(KERN_INFO "IPv6: frag: no memory for new fragment!\n");
+		/* Allocate buffer */
+		frag = alloc_skb(len + hlen + sizeof(struct frag_hdr) +
+				 hroom + troom, GFP_ATOMIC);
+		if (!frag) {
 			IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
 				      IPSTATS_MIB_FRAGFAILS);
 			err = -ENOMEM;

From: Joe Perches <[email protected]>
Date: Wed, 05 Nov 2014 14:39:21 -0800

Applied.