[PATCH 4.14 044/242] vxlan: Add needed_headroom for lower device

Greg Kroah-Hartman
2020-12-28T13:11:26Z

From: Sven Eckelmann <sven@narfation.org>

[ Upstream commit 0a35dc41fea67ac4495ce7584406bf9557a6e7d0 ]

It was observed that sending data via batadv over vxlan (on top of
wireguard) reduced the performance massively compared to raw ethernet or
batadv on raw ethernet. A check of perf data showed that the
vxlan_build_skb was calling all the time pskb_expand_head to allocate
enough headroom for:

min_headroom = LL_RESERVED_SPACE(dst->dev) + dst->header_len
+ VXLAN_HLEN + iphdr_len;

But the vxlan_config_apply only requested needed headroom for:

lowerdev->hard_header_len + VXLAN6_HEADROOM or VXLAN_HEADROOM

So it completely ignored the needed_headroom of the lower device. The first
caller of net_dev_xmit could therefore never make sure that enough headroom
was allocated for the rest of the transmit path.

Cc: Annika Wickert <annika.wickert@exaring.de>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Tested-by: Annika Wickert <aw@awlnx.space>
Link: https://lore.kernel.org/r/20201126125247.1047977-1-sven@narfation.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/vxlan.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 82efa5bbf568b..c21f28840f05b 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -3184,6 +3184,7 @@ static void vxlan_config_apply(struct net_device *dev,
dev->gso_max_segs = lowerdev->gso_max_segs;

needed_headroom = lowerdev->hard_header_len;
+ needed_headroom += lowerdev->needed_headroom;

max_mtu = lowerdev->mtu - (use_ipv6 ? VXLAN6_HEADROOM :
VXLAN_HEADROOM);
--
2.27.0