tree e53a86da175eb3ddb0f7c8fdadf56b523e6c3078
parent b1f84b43cc83a13ecda4f158d3ecae263d597a5c
author Sven Eckelmann <sven@narfation.org> 1637411997 +0100
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1637923723 +0100

batman-adv: Reserve needed_*room for fragments

commit c5cbfc87558168ef4c3c27ce36eba6b83391db19 upstream.

The batadv net_device is trying to propagate the needed_headroom and
needed_tailroom from the lower devices. This is needed to avoid cost
intensive reallocations using pskb_expand_head during the transmission.

But the fragmentation code split the skb's without adding extra room at the
end/beginning of the various fragments. This reduced the performance of
transmissions over complex scenarios (batadv on vxlan on wireguard) because
the lower devices had to perform the reallocations at least once.

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>
[ bp: 4.9 backported: adjust context. ]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>