linux-kernel - [PATCH NET 7/7] bpf: use pskb_realloc_headroom in bpf_out_neigh

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Date:   Mon, 12 Jul 2021 16:27:26 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH NET 7/7] bpf: use pskb_realloc_headroom in bpf_out_neigh_v4/6

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

Additionally this patch replaces commonly used dereferencing with variables.

Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
---
 net/core/filter.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 65ab4e2..cf6cd93 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2179,17 +2179,10 @@ static int bpf_out_neigh_v6(struct net *net, struct sk_buff *skb,
 	skb->tstamp = 0;
 
 	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, hh_len);
-		if (unlikely(!skb2)) {
-			kfree_skb(skb);
+		if (!skb)
 			return -ENOMEM;
-		}
-		if (skb->sk)
-			skb_set_owner_w(skb2, skb->sk);
-		consume_skb(skb);
-		skb = skb2;
 	}
 
 	rcu_read_lock_bh();
@@ -2286,17 +2279,10 @@ static int bpf_out_neigh_v4(struct net *net, struct sk_buff *skb,
 	skb->tstamp = 0;
 
 	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, hh_len);
-		if (unlikely(!skb2)) {
-			kfree_skb(skb);
+		if (!skb)
 			return -ENOMEM;
-		}
-		if (skb->sk)
-			skb_set_owner_w(skb2, skb->sk);
-		consume_skb(skb);
-		skb = skb2;
 	}
 
 	rcu_read_lock_bh();
-- 
1.8.3.1