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-rw-r--r--net/core/dev.c39
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