netdev - [PATCH v3 bpf-next 3/8] veth: Avoid drops by oversized packets when XDP is enabled

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Message-Id: <20180722151308.5480-4-toshiaki.makita1@gmail.com>
Date:   Mon, 23 Jul 2018 00:13:03 +0900
From:   Toshiaki Makita <toshiaki.makita1@...il.com>
To:     netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: [PATCH v3 bpf-next 3/8] veth: Avoid drops by oversized packets when XDP is enabled

From: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>

All oversized packets including GSO packets are dropped if XDP is
enabled on receiver side, so don't send such packets from peer.

Drop TSO and SCTP fragmentation features so that veth devices themselves
segment packets with XDP enabled. Also cap MTU accordingly.

Signed-off-by: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
---
 drivers/net/veth.c | 41 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 78fa08cb6e24..f5b72e937d9d 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -542,6 +542,23 @@ static int veth_get_iflink(const struct net_device *dev)
 	return iflink;
 }
 
+static netdev_features_t veth_fix_features(struct net_device *dev,
+					   netdev_features_t features)
+{
+	struct veth_priv *priv = netdev_priv(dev);
+	struct net_device *peer;
+
+	peer = rtnl_dereference(priv->peer);
+	if (peer) {
+		struct veth_priv *peer_priv = netdev_priv(peer);
+
+		if (peer_priv->_xdp_prog)
+			features &= ~NETIF_F_GSO_SOFTWARE;
+	}
+
+	return features;
+}
+
 static void veth_set_rx_headroom(struct net_device *dev, int new_hr)
 {
 	struct veth_priv *peer_priv, *priv = netdev_priv(dev);
@@ -591,14 +608,33 @@ static int veth_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 				goto err;
 			}
 		}
+
+		if (!old_prog) {
+			peer->hw_features &= ~NETIF_F_GSO_SOFTWARE;
+			peer->max_mtu = PAGE_SIZE - VETH_XDP_HEADROOM -
+				peer->hard_header_len -
+				SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+			if (peer->mtu > peer->max_mtu)
+				dev_set_mtu(peer, peer->max_mtu);
+		}
 	}
 
 	if (old_prog) {
-		if (!prog && dev->flags & IFF_UP)
-			veth_disable_xdp(dev);
+		if (!prog) {
+			if (dev->flags & IFF_UP)
+				veth_disable_xdp(dev);
+
+			if (peer) {
+				peer->hw_features |= NETIF_F_GSO_SOFTWARE;
+				peer->max_mtu = ETH_MAX_MTU;
+			}
+		}
 		bpf_prog_put(old_prog);
 	}
 
+	if ((!!old_prog ^ !!prog) && peer)
+		netdev_update_features(peer);
+
 	return 0;
 err:
 	priv->_xdp_prog = old_prog;
@@ -643,6 +679,7 @@ static const struct net_device_ops veth_netdev_ops = {
 	.ndo_poll_controller	= veth_poll_controller,
 #endif
 	.ndo_get_iflink		= veth_get_iflink,
+	.ndo_fix_features	= veth_fix_features,
 	.ndo_features_check	= passthru_features_check,
 	.ndo_set_rx_headroom	= veth_set_rx_headroom,
 	.ndo_bpf		= veth_xdp,
-- 
2.14.3