netfilter: conntrack: remove ignore stats

This counter increments when nf_conntrack_in sees a packet that already
has a conntrack attached or when the packet is marked as UNTRACKED.
Neither is an error.

The former is normal for loopback traffic. The second happens for
certain ICMPv6 packets or when nftables/ip(6)tables rules are in place.

In case someone needs to count UNTRACKED packets, or packets
that are marked as untracked before conntrack_in this can be done with
both nftables and ip(6)tables rules.

Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/linux/netfilter/nf_conntrack_common.h

···
 struct ip_conntrack_stat {
 	unsigned int found;
 	unsigned int invalid;
-	unsigned int ignore;
 	unsigned int insert;
 	unsigned int insert_failed;
 	unsigned int drop;

include/uapi/linux/netfilter/nfnetlink_conntrack.h

···
 	CTA_STATS_FOUND,
 	CTA_STATS_NEW,		/* no longer used */
 	CTA_STATS_INVALID,
-	CTA_STATS_IGNORE,
+	CTA_STATS_IGNORE,	/* no longer used */
 	CTA_STATS_DELETE,	/* no longer used */
 	CTA_STATS_DELETE_LIST,	/* no longer used */
 	CTA_STATS_INSERT,

net/netfilter/nf_conntrack_core.c

···
 	if (tmpl || ctinfo == IP_CT_UNTRACKED) {
 		/* Previously seen (loopback or untracked)?  Ignore. */
 		if ((tmpl && !nf_ct_is_template(tmpl)) ||
-		     ctinfo == IP_CT_UNTRACKED) {
-			NF_CT_STAT_INC_ATOMIC(state->net, ignore);
+		     ctinfo == IP_CT_UNTRACKED)
 			return NF_ACCEPT;
-		}
 		skb->_nfct = 0;
 	}
 

net/netfilter/nf_conntrack_netlink.c

···
 
 	if (nla_put_be32(skb, CTA_STATS_FOUND, htonl(st->found)) ||
 	    nla_put_be32(skb, CTA_STATS_INVALID, htonl(st->invalid)) ||
-	    nla_put_be32(skb, CTA_STATS_IGNORE, htonl(st->ignore)) ||
 	    nla_put_be32(skb, CTA_STATS_INSERT, htonl(st->insert)) ||
 	    nla_put_be32(skb, CTA_STATS_INSERT_FAILED,
 				htonl(st->insert_failed)) ||

net/netfilter/nf_conntrack_standalone.c

···
 		   st->found,
 		   0,
 		   st->invalid,
-		   st->ignore,
+		   0,
 		   0,
 		   0,
 		   st->insert,