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From: Sven Eckelmann <sven@narfation.org>
To: stable@vger.kernel.org
Cc: b.a.t.m.a.n@lists.open-mesh.org,
	Sven Eckelmann <sven@narfation.org>,
	Simon Wunderlich <sw@simonwunderlich.de>
Subject: [PATCH 4.19 4/4] batman-adv: Don't always reallocate the fragmentation skb head
Date: Sat, 20 Nov 2021 13:40:44 +0100	[thread overview]
Message-ID: <20211120124044.261086-5-sven@narfation.org> (raw)
In-Reply-To: <20211120124044.261086-1-sven@narfation.org>

commit 992b03b88e36254e26e9a4977ab948683e21bd9f upstream.

When a packet is fragmented by batman-adv, the original batman-adv header
is not modified. Only a new fragmentation is inserted between the original
one and the ethernet header. The code must therefore make sure that it has
a writable region of this size in the skbuff head.

But it is not useful to always reallocate the skbuff by this size even when
there would be more than enough headroom still in the skb. The reallocation
is just to costly during in this codepath.

Fixes: ee75ed88879a ("batman-adv: Fragment and send skbs larger than mtu")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
 net/batman-adv/fragmentation.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
index 2dbd870221e4..cc062b69fc8d 100644
--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -539,13 +539,14 @@ int batadv_frag_send_packet(struct sk_buff *skb,
-	/* Make room for the fragment header. */
-	if (batadv_skb_head_push(skb, header_size) < 0 ||
-	    pskb_expand_head(skb, header_size + ETH_HLEN, 0, GFP_ATOMIC) < 0) {
-		ret = -ENOMEM;
+	/* make sure that there is at least enough head for the fragmentation
+	 * and ethernet headers
+	 */
+	ret = skb_cow_head(skb, ETH_HLEN + header_size);
+	if (ret < 0)
 		goto put_primary_if;
-	}
+	skb_push(skb, header_size);
 	memcpy(skb->data, &frag_header, header_size);
 	/* Send the last fragment */

  parent reply	other threads:[~2021-11-20 12:40 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-20 12:40 [PATCH 4.19 0/4] batman-adv: Fixes for stable/linux-4.19.y Sven Eckelmann
2021-11-20 12:40 ` [PATCH 4.19 1/4] batman-adv: mcast: fix duplicate mcast packets in BLA backbone from LAN Sven Eckelmann
2021-11-23 12:35   ` Patch "batman-adv: mcast: fix duplicate mcast packets in BLA backbone from LAN" has been added to the 4.19-stable tree gregkh
2021-11-20 12:40 ` [PATCH 4.19 2/4] batman-adv: Consider fragmentation for needed_headroom Sven Eckelmann
2021-11-23 12:35   ` Patch "batman-adv: Consider fragmentation for needed_headroom" has been added to the 4.19-stable tree gregkh
2021-11-20 12:40 ` [PATCH 4.19 3/4] batman-adv: Reserve needed_*room for fragments Sven Eckelmann
2021-11-23 12:35   ` Patch "batman-adv: Reserve needed_*room for fragments" has been added to the 4.19-stable tree gregkh
2021-11-20 12:40 ` Sven Eckelmann [this message]
2021-11-23 12:35   ` Patch "batman-adv: Don't always reallocate the fragmentation skb head" " gregkh

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