Repository : ssh://git@diktynna/batman-adv On branch : master commit 3e3ff987876d3be70d928561acbefe5a48ab1654 Author: Sven Eckelmann &lt;sven(a)narfation.org&gt; Date: Thu Nov 26 18:24:49 2020 +0100 batman-adv: Don't always reallocate the fragmentation skb head 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: db56e4ecf5c2 ("batman-adv: Fragment and send skbs larger than mtu") Signed-off-by: Sven Eckelmann &lt;sven(a)narfation.org&gt; 3e3ff987876d3be70d928561acbefe5a48ab1654 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 8de1fb56..1f1f5b08 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 */