netfilter: conntrack: no need to pass ctinfo to error handler

It is never accessed for reading and the only places that write to it
are the icmp(6) handlers, which also set skb->nfct (and skb->nfctinfo).

The conntrack core specifically checks for attached skb->nfct after
->error() invocation and returns early in this case.

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

include/net/netfilter/nf_conntrack_l4proto.h

···
 	void (*destroy)(struct nf_conn *ct);
 
 	int (*error)(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
-		     unsigned int dataoff, enum ip_conntrack_info *ctinfo,
+		     unsigned int dataoff,
 		     u_int8_t pf, unsigned int hooknum);
 
 	/* Print out the per-protocol part of the tuple. Return like seq_* */

net/ipv4/netfilter/nf_conntrack_proto_icmp.c

···
 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
 static int
 icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
-		 enum ip_conntrack_info *ctinfo,
 		 unsigned int hooknum)
 {
 	struct nf_conntrack_tuple innertuple, origtuple;
 	const struct nf_conntrack_l4proto *innerproto;
 	const struct nf_conntrack_tuple_hash *h;
 	const struct nf_conntrack_zone *zone;
+	enum ip_conntrack_info ctinfo;
 	struct nf_conntrack_zone tmp;
 
 	NF_CT_ASSERT(skb->nfct == NULL);
···
 		return -NF_ACCEPT;
 	}
 
-	*ctinfo = IP_CT_RELATED;
+	ctinfo = IP_CT_RELATED;
 
 	h = nf_conntrack_find_get(net, zone, &innertuple);
 	if (!h) {
···
 	}
 
 	if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
-		*ctinfo += IP_CT_IS_REPLY;
+		ctinfo += IP_CT_IS_REPLY;
 
 	/* Update skb to refer to this connection */
 	skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
-	skb->nfctinfo = *ctinfo;
+	skb->nfctinfo = ctinfo;
 	return NF_ACCEPT;
 }
 
···
 static int
 icmp_error(struct net *net, struct nf_conn *tmpl,
 	   struct sk_buff *skb, unsigned int dataoff,
-	   enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
+	   u8 pf, unsigned int hooknum)
 {
 	const struct icmphdr *icmph;
 	struct icmphdr _ih;
···
 	    icmph->type != ICMP_REDIRECT)
 		return NF_ACCEPT;
 
-	return icmp_error_message(net, tmpl, skb, ctinfo, hooknum);
+	return icmp_error_message(net, tmpl, skb, hooknum);
 }
 
 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)

net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c

···
 icmpv6_error_message(struct net *net, struct nf_conn *tmpl,
 		     struct sk_buff *skb,
 		     unsigned int icmp6off,
-		     enum ip_conntrack_info *ctinfo,
 		     unsigned int hooknum)
 {
 	struct nf_conntrack_tuple intuple, origtuple;
 	const struct nf_conntrack_tuple_hash *h;
 	const struct nf_conntrack_l4proto *inproto;
+	enum ip_conntrack_info ctinfo;
 	struct nf_conntrack_zone tmp;
 
 	NF_CT_ASSERT(skb->nfct == NULL);
···
 		return -NF_ACCEPT;
 	}
 
-	*ctinfo = IP_CT_RELATED;
+	ctinfo = IP_CT_RELATED;
 
 	h = nf_conntrack_find_get(net, nf_ct_zone_tmpl(tmpl, skb, &tmp),
 				  &intuple);
···
 		return -NF_ACCEPT;
 	} else {
 		if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
-			*ctinfo += IP_CT_IS_REPLY;
+			ctinfo += IP_CT_IS_REPLY;
 	}
 
 	/* Update skb to refer to this connection */
 	skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
-	skb->nfctinfo = *ctinfo;
+	skb->nfctinfo = ctinfo;
 	return NF_ACCEPT;
 }
 
 static int
 icmpv6_error(struct net *net, struct nf_conn *tmpl,
 	     struct sk_buff *skb, unsigned int dataoff,
-	     enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
+	     u8 pf, unsigned int hooknum)
 {
 	const struct icmp6hdr *icmp6h;
 	struct icmp6hdr _ih;
···
 	if (icmp6h->icmp6_type >= 128)
 		return NF_ACCEPT;
 
-	return icmpv6_error_message(net, tmpl, skb, dataoff, ctinfo, hooknum);
+	return icmpv6_error_message(net, tmpl, skb, dataoff, hooknum);
 }
 
 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)

net/netfilter/nf_conntrack_core.c

···
 	 * inverse of the return code tells to the netfilter
 	 * core what to do with the packet. */
 	if (l4proto->error != NULL) {
-		ret = l4proto->error(net, tmpl, skb, dataoff, &ctinfo,
-				     pf, hooknum);
+		ret = l4proto->error(net, tmpl, skb, dataoff, pf, hooknum);
 		if (ret <= 0) {
 			NF_CT_STAT_INC_ATOMIC(net, error);
 			NF_CT_STAT_INC_ATOMIC(net, invalid);

net/netfilter/nf_conntrack_proto_dccp.c

···
 
 static int dccp_error(struct net *net, struct nf_conn *tmpl,
 		      struct sk_buff *skb, unsigned int dataoff,
-		      enum ip_conntrack_info *ctinfo,
 		      u_int8_t pf, unsigned int hooknum)
 {
 	struct dccp_hdr _dh, *dh;

net/netfilter/nf_conntrack_proto_sctp.c

···
 }
 
 static int sctp_error(struct net *net, struct nf_conn *tpl, struct sk_buff *skb,
-		      unsigned int dataoff, enum ip_conntrack_info *ctinfo,
+		      unsigned int dataoff,
 		      u8 pf, unsigned int hooknum)
 {
 	const struct sctphdr *sh;

net/netfilter/nf_conntrack_proto_tcp.c

···
 static int tcp_error(struct net *net, struct nf_conn *tmpl,
 		     struct sk_buff *skb,
 		     unsigned int dataoff,
-		     enum ip_conntrack_info *ctinfo,
 		     u_int8_t pf,
 		     unsigned int hooknum)
 {

net/netfilter/nf_conntrack_proto_udp.c

···
 static int udplite_error(struct net *net, struct nf_conn *tmpl,
 			 struct sk_buff *skb,
 			 unsigned int dataoff,
-			 enum ip_conntrack_info *ctinfo,
 			 u8 pf, unsigned int hooknum)
 {
 	unsigned int udplen = skb->len - dataoff;
···
 #endif
 
 static int udp_error(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
-		     unsigned int dataoff, enum ip_conntrack_info *ctinfo,
+		     unsigned int dataoff,
 		     u_int8_t pf,
 		     unsigned int hooknum)
 {