ipv6: remove daddr temp buffer in __ip6_make_skb

ipv6_push_nfrag_opts() doesn't change passed daddr, and so
__ip6_make_skb() doesn't actually need to keep an on-stack copy of
fl6->daddr. Set initially final_dst to fl6->daddr,
ipv6_push_nfrag_opts() will override it if needed, and get rid of extra
copies.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

net/ipv6/ip6_output.c

@@ -1843,7 +1843,7 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 {
 	struct sk_buff *skb, *tmp_skb;
 	struct sk_buff **tail_skb;
-	struct in6_addr final_dst_buf, *final_dst = &final_dst_buf;
+	struct in6_addr *final_dst;
 	struct ipv6_pinfo *np = inet6_sk(sk);
 	struct net *net = sock_net(sk);
 	struct ipv6hdr *hdr;
@@ -1873,9 +1873,9 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 
 	/* Allow local fragmentation. */
 	skb->ignore_df = ip6_sk_ignore_df(sk);
-
-	*final_dst = fl6->daddr;
 	__skb_pull(skb, skb_network_header_len(skb));
+
+	final_dst = &fl6->daddr;
 	if (opt && opt->opt_flen)
 		ipv6_push_frag_opts(skb, opt, &proto);
 	if (opt && opt->opt_nflen)
@@ -1895,7 +1895,6 @@ struct sk_buff *__ip6_make_skb(struct sock *sk,
 
 	skb->priority = sk->sk_priority;
 	skb->mark = cork->base.mark;
-
 	skb->tstamp = cork->base.transmit_time;
 
 	ip6_cork_steal_dst(skb, cork);