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Subject[PATCH 4.15 076/122] tuntap: correctly add the missing XDP flush
4.15-stable review patch.  If anyone has any objections, please let me know.


From: Jason Wang <>

[ Upstream commit 1bb4f2e868a2891ab8bc668b8173d6ccb8c4ce6f ]

We don't flush batched XDP packets through xdp_do_flush_map(), this
will cause packets stall at TX queue. Consider we don't do XDP on NAPI
poll(), the only possible fix is to call xdp_do_flush_map()
immediately after xdp_do_redirect().

Note, this in fact won't try to batch packets through devmap, we could
address in the future.

Reported-by: Christoffer Dall <>
Fixes: 761876c857cb ("tap: XDP support")
Signed-off-by: Jason Wang <>
Signed-off-by: David S. Miller <>
Signed-off-by: Greg Kroah-Hartman <>
drivers/net/tun.c | 1 +
1 file changed, 1 insertion(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1490,6 +1490,7 @@ static struct sk_buff *tun_build_skb(str
alloc_frag->offset += buflen;
err = xdp_do_redirect(tun->dev, &xdp, xdp_prog);
+ xdp_do_flush_map();
if (err)
goto err_redirect;

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