tuntap: correctly add the missing XDP flush

BugLink: http://bugs.launchpad.net/bugs/1755179
[ 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 <christoffer.dall@linaro.org>
Fixes: 761876c857cb ("tap: XDP support")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index e29cd5c7d39fb0ec0bd0f0f5eaf2d643049e0775..5f04f784bc97fa45e7a02336e858cda0f0a74851 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1490,6 +1490,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
                        get_page(alloc_frag->page);
                        alloc_frag->offset += buflen;
                        err = xdp_do_redirect(tun->dev, &xdp, xdp_prog);
+                       xdp_do_flush_map();
                        if (err)
                                goto err_redirect;
                        rcu_read_unlock();