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tun: correct header offsets in napi frags mode 

Tun in IFF_NAPI_FRAGS mode calls napi_gro_frags. Unlike netif_rx and
netif_gro_receive, this expects skb->data to point to the mac layer.

But skb_probe_transport_header, __skb_get_hash_symmetric, and
xdp_do_generic in tun_get_user need skb->data to point to the network
header. Flow dissection also needs skb->protocol set, so
eth_type_trans has to be called.

Ensure the link layer header lies in linear as eth_type_trans pulls
ETH_HLEN. Then take the same code paths for frags as for not frags.
Push the link layer header back just before calling napi_gro_frags.

By pulling up to ETH_HLEN from frag0 into linear, this disables the
frag0 optimization in the special case when IFF_NAPI_FRAGS is used
with zero length iov[0] (and thus empty skb->linear).

Fixes: 90e33d4594 ("tun: enable napi_gro_frags() for TUN/TAP driver")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Petar Penkov <ppenkov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2020-05-30 15:41:31 -04:00 committed by David S. Miller
parent 4e4f4ce6ab
commit 96aa1b22bd
1 changed files with 10 additions and 4 deletions
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14
drivers/net/tun.c
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@ -1872,8 +1872,11 @@ drop:
skb->dev = tun->dev;
break;
case IFF_TAP:
if (!frags)
skb->protocol = eth_type_trans(skb, tun->dev);
if (frags && !pskb_may_pull(skb, ETH_HLEN)) {
err = -ENOMEM;
goto drop;
}
skb->protocol = eth_type_trans(skb, tun->dev);
break;
}
@ -1930,9 +1933,12 @@ drop:
}
if (frags) {
u32 headlen;
/* Exercise flow dissector code path. */
u32 headlen = eth_get_headlen(tun->dev, skb->data,
skb_headlen(skb));
skb_push(skb, ETH_HLEN);
headlen = eth_get_headlen(tun->dev, skb->data,
skb_headlen(skb));
if (unlikely(headlen > skb_headlen(skb))) {
this_cpu_inc(tun->pcpu_stats->rx_dropped);