netdev-afxdp: add afxdp specific maximum MTU check

Drivers natively supporting AF_XDP will check that a configured MTU size will not exceed the allowed size for AF_XDP. However, when the skb compatibility mode is used there is no check and any value is accepted. This, for example, is the case when using the TAP interface. This fix adds a check to make sure only AF_XDP valid values are excepted. Signed-off-by: Eelco Chaudron <[email protected]> Signed-off-by: William Tu <[email protected]>
Dragmaf93 · Nov 19, 2019 · 52b5a5c · 52b5a5c
1 parent 433a3fa
commit 52b5a5c
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diff --git a/lib/netdev-afxdp.c b/lib/netdev-afxdp.c
@@ -1084,6 +1084,23 @@ netdev_afxdp_destruct(struct netdev *netdev)
     ovs_mutex_destroy(&dev->mutex);
 }
 
+int
+netdev_afxdp_verify_mtu_size(const struct netdev *netdev OVS_UNUSED, int mtu)
+{
+    /*
+     * If a device is used in xdpmode skb, no driver-specific MTU size is
+     * checked and any value is allowed resulting in packet drops.
+     * This check will verify the maximum supported value based on the
+     * buffer size allocated and the additional headroom required.
+     */
+    if (mtu > (FRAME_SIZE - OVS_XDP_HEADROOM -
+               XDP_PACKET_HEADROOM - VLAN_ETH_HEADER_LEN)) {
+        return EINVAL;
+    }
+
+    return 0;
+}
+
 int
 netdev_afxdp_get_custom_stats(const struct netdev *netdev,
                               struct netdev_custom_stats *custom_stats)

diff --git a/lib/netdev-afxdp.h b/lib/netdev-afxdp.h
@@ -39,6 +39,7 @@ int netdev_afxdp_rxq_construct(struct netdev_rxq *rxq_);
 void netdev_afxdp_rxq_destruct(struct netdev_rxq *rxq_);
 int netdev_afxdp_construct(struct netdev *netdev_);
 void netdev_afxdp_destruct(struct netdev *netdev_);
+int netdev_afxdp_verify_mtu_size(const struct netdev *netdev, int mtu);
 
 int netdev_afxdp_rxq_recv(struct netdev_rxq *rxq_,
                           struct dp_packet_batch *batch,

diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c
@@ -1593,6 +1593,15 @@ netdev_linux_set_mtu(struct netdev *netdev_, int mtu)
         goto exit;
     }
 
+#ifdef HAVE_AF_XDP
+    if (netdev_get_class(netdev_) == &netdev_afxdp_class) {
+        error = netdev_afxdp_verify_mtu_size(netdev_, mtu);
+        if (error) {
+            goto exit;
+        }
+    }
+#endif
+
     if (netdev->cache_valid & VALID_MTU) {
         error = netdev->netdev_mtu_error;
         if (error || netdev->mtu == mtu) {