1 files changed, 39 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 6cc8a70350ac..a76021c71207 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3993,6 +3993,45 @@ static int __init netdev_dma_register(void)
 static int __init netdev_dma_register(void) { return -ENODEV; }
 #endif /* CONFIG_NET_DMA */
 
+/**
+ *      netdev_compute_feature - compute conjunction of two feature sets
+ *      @all: first feature set
+ *      @one: second feature set
+ *
+ *      Computes a new feature set after adding a device with feature set
+ *      @one to the master device with current feature set @all.  Returns
+ *      the new feature set.
+ */
+int netdev_compute_features(unsigned long all, unsigned long one)
+{
+        /* if device needs checksumming, downgrade to hw checksumming */
+        if (all & NETIF_F_NO_CSUM && !(one & NETIF_F_NO_CSUM))
+                all ^= NETIF_F_NO_CSUM | NETIF_F_HW_CSUM;
+
+        /* if device can't do all checksum, downgrade to ipv4/ipv6 */
+        if (all & NETIF_F_HW_CSUM && !(one & NETIF_F_HW_CSUM))
+                all ^= NETIF_F_HW_CSUM
+                        | NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM;
+
+        if (one & NETIF_F_GSO)
+                one |= NETIF_F_GSO_SOFTWARE;
+        one |= NETIF_F_GSO;
+
+        /* If even one device supports robust GSO, enable it for all. */
+        if (one & NETIF_F_GSO_ROBUST)
+                all |= NETIF_F_GSO_ROBUST;
+
+        all &= one | NETIF_F_LLTX;
+
+        if (!(all & NETIF_F_ALL_CSUM))
+                all &= ~NETIF_F_SG;
+        if (!(all & NETIF_F_SG))
+                all &= ~NETIF_F_GSO_MASK;
+
+        return all;
+}
+EXPORT_SYMBOL(netdev_compute_features);
+
 /*
  *      Initialize the DEV module. At boot time this walks the device list and
  *      unhooks any devices that fail to initialise (normally hardware not