net/macb: add RX checksum offload feature

When RX checksum offload is enabled at GEM level (bit 24 set in the Network
Control Register), frames with invalid IP, TCP or UDP checksums are
discarted even if promiscuous mode is enabled (bit 4 set in the Network Control
Register).

This was verified with a simple userspace program, which corrupts UDP checksum
using libnetfilter_queue.

Then both IFF_PROMISC bit must be clear in dev->flags and NETIF_F_RXCSUM bit
must be set in dev->features to enable RX checksum offload at GEM level. This
way tcpdump is still able to capture corrupted frames.

Also skb->ip_summed is set to CHECKSUM_UNNECESSARY only when both TCP/IP or
UDP/IP checksums were verified by the GEM. Indeed the GEM may verify only IP
checksum but not the one for ICMP (or other protocol than TCP or UDP).

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 32 insertions, 4 deletions

diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
index cc36269474a6..6836f88dbdc6 100644
--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c
@@ -765,6 +765,10 @@ static int gem_rx(struct macb *bp, int budget)
 
 		skb->protocol = eth_type_trans(skb, bp->dev);
 		skb_checksum_none_assert(skb);
+		if (bp->dev->features & NETIF_F_RXCSUM &&
+		    !(bp->dev->flags & IFF_PROMISC) &&
+		    GEM_BFEXT(RX_CSUM, ctrl) & GEM_RX_CSUM_CHECKED_MASK)
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
 
 		bp->stats.rx_packets++;
 		bp->stats.rx_bytes += skb->len;
@@ -1549,6 +1553,8 @@ static void macb_init_hw(struct macb *bp)
 	config |= MACB_BIT(BIG);		/* Receive oversized frames */
 	if (bp->dev->flags & IFF_PROMISC)
 		config |= MACB_BIT(CAF);	/* Copy All Frames */
+	else if (macb_is_gem(bp) && bp->dev->features & NETIF_F_RXCSUM)
+		config |= GEM_BIT(RXCOEN);
 	if (!(bp->dev->flags & IFF_BROADCAST))
 		config |= MACB_BIT(NBC);	/* No BroadCast */
 	config |= macb_dbw(bp);
@@ -1662,13 +1668,22 @@ void macb_set_rx_mode(struct net_device *dev)
 
 	cfg = macb_readl(bp, NCFGR);
 
-	if (dev->flags & IFF_PROMISC)
+	if (dev->flags & IFF_PROMISC) {
 		/* Enable promiscuous mode */
 		cfg |= MACB_BIT(CAF);
-	else if (dev->flags & (~IFF_PROMISC))
-		 /* Disable promiscuous mode */
+
+		/* Disable RX checksum offload */
+		if (macb_is_gem(bp))
+			cfg &= ~GEM_BIT(RXCOEN);
+	} else {
+		/* Disable promiscuous mode */
 		cfg &= ~MACB_BIT(CAF);
 
+		/* Enable RX checksum offload only if requested */
+		if (macb_is_gem(bp) && dev->features & NETIF_F_RXCSUM)
+			cfg |= GEM_BIT(RXCOEN);
+	}
+
 	if (dev->flags & IFF_ALLMULTI) {
 		/* Enable all multicast mode */
 		macb_or_gem_writel(bp, HRB, -1);
@@ -1947,6 +1962,19 @@ static int macb_set_features(struct net_device *netdev,
 		gem_writel(bp, DMACFG, dmacfg);
 	}
 
+	/* RX checksum offload */
+	if ((changed & NETIF_F_RXCSUM) && macb_is_gem(bp)) {
+		u32 netcfg;
+
+		netcfg = gem_readl(bp, NCFGR);
+		if (features & NETIF_F_RXCSUM &&
+		    !(netdev->flags & IFF_PROMISC))
+			netcfg |= GEM_BIT(RXCOEN);
+		else
+			netcfg &= ~GEM_BIT(RXCOEN);
+		gem_writel(bp, NCFGR, netcfg);
+	}
+
 	return 0;
 }
 
@@ -2150,7 +2178,7 @@ static int __init macb_probe(struct platform_device *pdev)
 	dev->hw_features = NETIF_F_SG;
 	/* Checksum offload is only available on gem with packet buffer */
 	if (macb_is_gem(bp) && !(bp->caps & MACB_CAPS_FIFO_MODE))
-		dev->hw_features |= NETIF_F_HW_CSUM;
+		dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_RXCSUM;
 	if (bp->caps & MACB_CAPS_SG_DISABLED)
 		dev->hw_features &= ~NETIF_F_SG;
 	dev->features = dev->hw_features;