netfilter: conntrack: simplify nf_conntrack_alter_reply

nf_conntrack_alter_reply doesn't do helper reassignment anymore.
Remove the comments that make this claim.

Furthermore, remove dead code from the function and place ot
in nf_conntrack.h.

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

include/net/netfilter/nf_conntrack.h

···
 	return read_pnet(&ct->ct_net);
 }
 
-/* Alter reply tuple (maybe alter helper). */
-void nf_conntrack_alter_reply(struct nf_conn *ct,
-			      const struct nf_conntrack_tuple *newreply);
-
 /* Is this tuple taken? (ignoring any belonging to the given
    conntrack). */
 int nf_conntrack_tuple_taken(const struct nf_conntrack_tuple *tuple,
···
 static inline bool nf_is_loopback_packet(const struct sk_buff *skb)
 {
 	return skb->dev && skb->skb_iif && skb->dev->flags & IFF_LOOPBACK;
+}
+
+static inline void nf_conntrack_alter_reply(struct nf_conn *ct,
+					    const struct nf_conntrack_tuple *newreply)
+{
+	/* Must be unconfirmed, so not in hash table yet */
+	if (WARN_ON(nf_ct_is_confirmed(ct)))
+		return;
+
+	ct->tuplehash[IP_CT_DIR_REPLY].tuple = *newreply;
 }
 
 #define nfct_time_stamp ((u32)(jiffies))

net/netfilter/nf_conntrack_core.c

···
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_in);
 
-/* Alter reply tuple (maybe alter helper).  This is for NAT, and is
-   implicitly racy: see __nf_conntrack_confirm */
-void nf_conntrack_alter_reply(struct nf_conn *ct,
-			      const struct nf_conntrack_tuple *newreply)
-{
-	struct nf_conn_help *help = nfct_help(ct);
-
-	/* Should be unconfirmed, so not in hash table yet */
-	WARN_ON(nf_ct_is_confirmed(ct));
-
-	nf_ct_dump_tuple(newreply);
-
-	ct->tuplehash[IP_CT_DIR_REPLY].tuple = *newreply;
-	if (ct->master || (help && !hlist_empty(&help->expectations)))
-		return;
-}
-EXPORT_SYMBOL_GPL(nf_conntrack_alter_reply);
-
 /* Refresh conntrack for this many jiffies and do accounting if do_acct is 1 */
 void __nf_ct_refresh_acct(struct nf_conn *ct,
 			  enum ip_conntrack_info ctinfo,

net/netfilter/nf_conntrack_helper.c

···
 	struct nf_conntrack_helper *helper = NULL;
 	struct nf_conn_help *help;
 
-	/* We already got a helper explicitly attached. The function
-	 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
-	 * the helper up again. Since now the user is in full control of
-	 * making consistent helper configurations, skip this automatic
-	 * re-lookup, otherwise we'll lose the helper.
-	 */
+	/* We already got a helper explicitly attached (e.g. nft_ct) */
 	if (test_bit(IPS_HELPER_BIT, &ct->status))
 		return 0;