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    Subject[PATCH 5.4 042/453] vxlan: Add needed_headroom for lower device
    Date
    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 630ac00a34ede..3753cf0942865 100644
    --- a/drivers/net/vxlan.c
    +++ b/drivers/net/vxlan.c
    @@ -3538,6 +3538,7 @@ 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


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