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 <christoffer.d...@linaro.org>
Fixes: 761876c857cb ("tap: XDP support")
Signed-off-by: Jason Wang <jasow...@redhat.com>
 drivers/net/tun.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 63d39fe6..7433bb2 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1663,6 +1663,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct 
                        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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