linux-kernel - [PATCH net-next v2 03/10] ipv6: remove daddr temp buffer in __ip6_make

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Message-Id: <e622cbe82ae21b740cb818abc9f6efe02cb0dede.1643243772.git.asml.silence@gmail.com>
Date:   Thu, 27 Jan 2022 00:36:24 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        linux-kernel@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [PATCH net-next v2 03/10] 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: Pavel Begunkov <asml.silence@...il.com>
---
 net/ipv6/ip6_output.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 14d607ccfeea..4acd577d5ec5 100644
--- a/net/ipv6/ip6_output.c
+++ b/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);
-- 
2.34.1