xen-netback: enable IPv6 TCP GSO to the guest

This patch adds code to handle SKB_GSO_TCPV6 skbs and construct appropriate
extra or prefix segments to pass the large packet to the frontend. New
xenstore flags, feature-gso-tcpv6 and feature-gso-tcpv6-prefix, are sampled
to determine if the frontend is capable of handling such packets.

Signed-off-by: Paul Durrant <[e-mail]>
Cc: Wei Liu <[e-mail]>
Cc: David Vrabel <[e-mail]>
Cc: Ian Campbell <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/xen-netback/common.h

···
 struct xenvif_rx_meta {
 	int id;
 	int size;
+	int gso_type;
 	int gso_size;
 };
+
+#define GSO_BIT(type) \
+	(1 << XEN_NETIF_GSO_TYPE_ ## type)
 
 /* Discriminate from any valid pending_idx value. */
 #define INVALID_PENDING_IDX 0xFFFF
···
 	u8               fe_dev_addr[6];
 
 	/* Frontend feature information. */
+	int gso_mask;
+	int gso_prefix_mask;
+
 	u8 can_sg:1;
-	u8 gso:1;
-	u8 gso_prefix:1;
 	u8 ip_csum:1;
 	u8 ipv6_csum:1;
 

drivers/net/xen-netback/interface.c

···
 
 	if (!vif->can_sg)
 		features &= ~NETIF_F_SG;
-	if (!vif->gso && !vif->gso_prefix)
+	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV4))
 		features &= ~NETIF_F_TSO;
+	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV6))
+		features &= ~NETIF_F_TSO6;
 	if (!vif->ip_csum)
 		features &= ~NETIF_F_IP_CSUM;
 	if (!vif->ipv6_csum)
···
 	dev->netdev_ops	= &xenvif_netdev_ops;
 	dev->hw_features = NETIF_F_SG |
 		NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
-		NETIF_F_TSO;
+		NETIF_F_TSO | NETIF_F_TSO6;
 	dev->features = dev->hw_features | NETIF_F_RXCSUM;
 	SET_ETHTOOL_OPS(dev, &xenvif_ethtool_ops);
 

drivers/net/xen-netback/netback.c

···
 	int max = DIV_ROUND_UP(vif->dev->mtu, PAGE_SIZE);
 
 	/* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */
-	if (vif->can_sg || vif->gso || vif->gso_prefix)
+	if (vif->can_sg || vif->gso_mask || vif->gso_prefix_mask)
 		max += MAX_SKB_FRAGS + 1; /* extra_info + frags */
 
 	return max;
···
 	req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
 
 	meta = npo->meta + npo->meta_prod++;
+	meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;
 	meta->gso_size = 0;
 	meta->size = 0;
 	meta->id = req->id;
···
 	struct gnttab_copy *copy_gop;
 	struct xenvif_rx_meta *meta;
 	unsigned long bytes;
+	int gso_type;
 
 	/* Data must not cross a page boundary. */
 	BUG_ON(size + offset > PAGE_SIZE<<compound_order(page));
···
 		}
 
 		/* Leave a gap for the GSO descriptor. */
-		if (*head && skb_shinfo(skb)->gso_size && !vif->gso_prefix)
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+			gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
+		else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+			gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
+		else
+			gso_type = XEN_NETIF_GSO_TYPE_NONE;
+
+		if (*head && ((1 << gso_type) & vif->gso_mask))
 			vif->rx.req_cons++;
 
 		*head = 0; /* There must be something in this buffer now. */
···
 	unsigned char *data;
 	int head = 1;
 	int old_meta_prod;
+	int gso_type;
+	int gso_size;
 
 	old_meta_prod = npo->meta_prod;
 
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
+		gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
+		gso_size = skb_shinfo(skb)->gso_size;
+	} else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) {
+		gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
+		gso_size = skb_shinfo(skb)->gso_size;
+	} else {
+		gso_type = XEN_NETIF_GSO_TYPE_NONE;
+		gso_size = 0;
+	}
+
 	/* Set up a GSO prefix descriptor, if necessary */
-	if (skb_shinfo(skb)->gso_size && vif->gso_prefix) {
+	if ((1 << skb_shinfo(skb)->gso_type) & vif->gso_prefix_mask) {
 		req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
 		meta = npo->meta + npo->meta_prod++;
-		meta->gso_size = skb_shinfo(skb)->gso_size;
+		meta->gso_type = gso_type;
+		meta->gso_size = gso_size;
 		meta->size = 0;
 		meta->id = req->id;
 	}
···
 	req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
 	meta = npo->meta + npo->meta_prod++;
 
-	if (!vif->gso_prefix)
-		meta->gso_size = skb_shinfo(skb)->gso_size;
-	else
+	if ((1 << gso_type) & vif->gso_mask) {
+		meta->gso_type = gso_type;
+		meta->gso_size = gso_size;
+	} else {
+		meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;
 		meta->gso_size = 0;
+	}
 
 	meta->size = 0;
 	meta->id = req->id;
···
 
 		vif = netdev_priv(skb->dev);
 
-		if (vif->meta[npo.meta_cons].gso_size && vif->gso_prefix) {
+		if ((1 << vif->meta[npo.meta_cons].gso_type) &
+		    vif->gso_prefix_mask) {
 			resp = RING_GET_RESPONSE(&vif->rx,
 						 vif->rx.rsp_prod_pvt++);
 
···
 					vif->meta[npo.meta_cons].size,
 					flags);
 
-		if (vif->meta[npo.meta_cons].gso_size && !vif->gso_prefix) {
+		if ((1 << vif->meta[npo.meta_cons].gso_type) &
+		    vif->gso_mask) {
 			struct xen_netif_extra_info *gso =
 				(struct xen_netif_extra_info *)
 				RING_GET_RESPONSE(&vif->rx,
···
 
 			resp->flags |= XEN_NETRXF_extra_info;
 
+			gso->u.gso.type = vif->meta[npo.meta_cons].gso_type;
 			gso->u.gso.size = vif->meta[npo.meta_cons].gso_size;
-			gso->u.gso.type = XEN_NETIF_GSO_TYPE_TCPV4;
 			gso->u.gso.pad = 0;
 			gso->u.gso.features = 0;
 

drivers/net/xen-netback/xenbus.c

···
 		val = 0;
 	vif->can_sg = !!val;
 
+	vif->gso_mask = 0;
+	vif->gso_prefix_mask = 0;
+
 	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4",
 			 "%d", &val) < 0)
 		val = 0;
-	vif->gso = !!val;
+	if (val)
+		vif->gso_mask |= GSO_BIT(TCPV4);
 
 	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4-prefix",
 			 "%d", &val) < 0)
 		val = 0;
-	vif->gso_prefix = !!val;
+	if (val)
+		vif->gso_prefix_mask |= GSO_BIT(TCPV4);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_mask |= GSO_BIT(TCPV6);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6-prefix",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_prefix_mask |= GSO_BIT(TCPV6);
+
+	if (vif->gso_mask & vif->gso_prefix_mask) {
+		xenbus_dev_fatal(dev, err,
+				 "%s: gso and gso prefix flags are not "
+				 "mutually exclusive",
+				 dev->otherend);
+		return -EOPNOTSUPP;
+	}
 
 	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
 			 "%d", &val) < 0)

include/xen/interface/io/netif.h

···
 #define  XEN_NETIF_EXTRA_FLAG_MORE	(1U<<_XEN_NETIF_EXTRA_FLAG_MORE)
 
 /* GSO types */
+#define XEN_NETIF_GSO_TYPE_NONE		(0)
 #define XEN_NETIF_GSO_TYPE_TCPV4	(1)
 #define XEN_NETIF_GSO_TYPE_TCPV6	(2)