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From:   Vasily Averin <vvs@virtuozzo.com>
Subject: [PATCH NET 4/7] ipv4: use pskb_realloc_headroom in ip_finish_output2
To:     "David S. Miller" <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <eric.dumazet@gmail.com>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <74e90fba-df9f-5078-13de-41df54d2b257@virtuozzo.com>
 <cover.1626093470.git.vvs@virtuozzo.com>
Message-ID: <f5ce9d4c-3a38-40ea-1e7f-b62a721a20c5@virtuozzo.com>
Date:   Mon, 12 Jul 2021 16:27:03 +0300
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Precedence: bulk

Unlike skb_realloc_headroom, new helper pskb_realloc_headroom
does not allocate a new skb if possible.

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
 net/ipv4/ip_output.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index c3efc7d..0f66483 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -198,19 +198,11 @@ static int ip_finish_output2(struct net *net, struct sock *sk, struct sk_buff *s
 	} else if (rt->rt_type == RTN_BROADCAST)
 		IP_UPD_PO_STATS(net, IPSTATS_MIB_OUTBCAST, skb->len);
 
-	/* Be paranoid, rather than too clever. */
 	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
-		struct sk_buff *skb2;
+		skb = pskb_realloc_headroom(skb, hh_len);
 
-		skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
-		if (!skb2) {
-			kfree_skb(skb);
+		if (!skb)
 			return -ENOMEM;
-		}
-		if (skb->sk)
-			skb_set_owner_w(skb2, skb->sk);
-		consume_skb(skb);
-		skb = skb2;
 	}
 
 	if (lwtunnel_xmit_redirect(dst->lwtstate)) {
-- 
1.8.3.1