net: Convert LIMIT_NETDEBUG to net_dbg_ratelimited

Use the more common dynamic_debug capable net_dbg_ratelimited
and remove the LIMIT_NETDEBUG macro.

All messages are still ratelimited.

Some KERN_<LEVEL> uses are changed to KERN_DEBUG.

This may have some negative impact on messages that were
emitted at KERN_INFO that are not not enabled at all unless
DEBUG is defined or dynamic_debug is enabled.  Even so,
these messages are now _not_ emitted by default.

This also eliminates the use of the net_msg_warn sysctl
"/proc/sys/net/core/warnings".  For backward compatibility,
the sysctl is not removed, but it has no function.  The extern
declaration of net_msg_warn is removed from sock.h and made
static in net/core/sysctl_net_core.c

Miscellanea:

o Update the sysctl documentation
o Remove the embedded uses of pr_fmt
o Coalesce format fragments
o Realign arguments

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 601d896..a7bbbe4 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -184,7 +184,7 @@
 	int ret;
 
 	if (opt->dsthao) {
-		LIMIT_NETDEBUG(KERN_DEBUG "hao duplicated\n");
+		net_dbg_ratelimited("hao duplicated\n");
 		goto discard;
 	}
 	opt->dsthao = opt->dst1;
@@ -193,14 +193,14 @@
 	hao = (struct ipv6_destopt_hao *)(skb_network_header(skb) + optoff);
 
 	if (hao->length != 16) {
-		LIMIT_NETDEBUG(
-			KERN_DEBUG "hao invalid option length = %d\n", hao->length);
+		net_dbg_ratelimited("hao invalid option length = %d\n",
+				    hao->length);
 		goto discard;
 	}
 
 	if (!(ipv6_addr_type(&hao->addr) & IPV6_ADDR_UNICAST)) {
-		LIMIT_NETDEBUG(
-			KERN_DEBUG "hao is not an unicast addr: %pI6\n", &hao->addr);
+		net_dbg_ratelimited("hao is not an unicast addr: %pI6\n",
+				    &hao->addr);
 		goto discard;
 	}
 
@@ -551,8 +551,8 @@
 		memcpy(&IP6CB(skb)->ra, nh + optoff + 2, sizeof(IP6CB(skb)->ra));
 		return true;
 	}
-	LIMIT_NETDEBUG(KERN_DEBUG "ipv6_hop_ra: wrong RA length %d\n",
-		       nh[optoff + 1]);
+	net_dbg_ratelimited("ipv6_hop_ra: wrong RA length %d\n",
+			    nh[optoff + 1]);
 	kfree_skb(skb);
 	return false;
 }
@@ -566,8 +566,8 @@
 	u32 pkt_len;
 
 	if (nh[optoff + 1] != 4 || (optoff & 3) != 2) {
-		LIMIT_NETDEBUG(KERN_DEBUG "ipv6_hop_jumbo: wrong jumbo opt length/alignment %d\n",
-			       nh[optoff+1]);
+		net_dbg_ratelimited("ipv6_hop_jumbo: wrong jumbo opt length/alignment %d\n",
+				    nh[optoff+1]);
 		IP6_INC_STATS_BH(net, ipv6_skb_idev(skb),
 				 IPSTATS_MIB_INHDRERRORS);
 		goto drop;