diff mbox series

[3/3] batman-adv: Don't always reallocate the fragmentation skb head

Message ID 20201127173849.19208-4-sw@simonwunderlich.de (mailing list archive)
State Accepted
Delegated to: Netdev Maintainers
Headers show
Series [1/3] batman-adv: Consider fragmentation for needed_headroom | expand

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netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 19 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
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netdev/stable success Stable not CCed

Commit Message

Simon Wunderlich Nov. 27, 2020, 5:38 p.m. UTC 
From: Sven Eckelmann <sven@narfation.org>

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>
---
 net/batman-adv/fragmentation.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
index 8de1fb567fd7..1f1f5b0873b2 100644
--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -527,13 +527,14 @@  int batadv_frag_send_packet(struct sk_buff *skb,
 		frag_header.no++;
 	}
 
-	/* 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 */