xen-netback: pass hash value to the frontend

My recent patch to include/xen/interface/io/netif.h defines a new extra
info type that can be used to pass hash values between backend and guest
frontend.

This patch adds code to xen-netback to pass hash values calculated for
guest receive-side packets (i.e. netback transmit side) to the frontend.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netback/interface.c

@@ -158,8 +158,17 @@ static u16 xenvif_select_queue(struct net_device *dev, struct sk_buff *skb,
 	struct xenvif *vif = netdev_priv(dev);
 	unsigned int size = vif->hash.size;
 
-	if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)
-		return fallback(dev, skb) % dev->real_num_tx_queues;
+	if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE) {
+		u16 index = fallback(dev, skb) % dev->real_num_tx_queues;
+
+		/* Make sure there is no hash information in the socket
+		 * buffer otherwise it would be incorrectly forwarded
+		 * to the frontend.
+		 */
+		skb_clear_hash(skb);
+
+		return index;
+	}
 
 	xenvif_set_skb_hash(vif, skb);
 

drivers/net/xen-netback/netback.c

@@ -168,6 +168,8 @@ static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue)
 	needed = DIV_ROUND_UP(skb->len, XEN_PAGE_SIZE);
 	if (skb_is_gso(skb))
 		needed++;
+	if (skb->sw_hash)
+		needed++;
 
 	do {
 		prod = queue->rx.sring->req_prod;
@@ -285,6 +287,8 @@ struct gop_frag_copy {
 	struct xenvif_rx_meta *meta;
 	int head;
 	int gso_type;
+	int protocol;
+	int hash_present;
 
 	struct page *page;
 };
@@ -331,8 +335,15 @@ static void xenvif_setup_copy_gop(unsigned long gfn,
 	npo->copy_off += *len;
 	info->meta->size += *len;
 
+	if (!info->head)
+		return;
+
 	/* Leave a gap for the GSO descriptor. */
-	if (info->head && ((1 << info->gso_type) & queue->vif->gso_mask))
+	if ((1 << info->gso_type) & queue->vif->gso_mask)
+		queue->rx.req_cons++;
+
+	/* Leave a gap for the hash extra segment. */
+	if (info->hash_present)
 		queue->rx.req_cons++;
 
 	info->head = 0; /* There must be something in this buffer now */
@@ -367,6 +378,11 @@ static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb
 		.npo = npo,
 		.head = *head,
 		.gso_type = XEN_NETIF_GSO_TYPE_NONE,
+		/* xenvif_set_skb_hash() will have either set a s/w
+		 * hash or cleared the hash depending on
+		 * whether the the frontend wants a hash for this skb.
+		 */
+		.hash_present = skb->sw_hash,
 	};
 	unsigned long bytes;
 
@@ -555,6 +571,7 @@ void xenvif_kick_thread(struct xenvif_queue *queue)
 
 static void xenvif_rx_action(struct xenvif_queue *queue)
 {
+	struct xenvif *vif = queue->vif;
 	s8 status;
 	u16 flags;
 	struct xen_netif_rx_response *resp;
@@ -590,9 +607,10 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
 	gnttab_batch_copy(queue->grant_copy_op, npo.copy_prod);
 
 	while ((skb = __skb_dequeue(&rxq)) != NULL) {
+		struct xen_netif_extra_info *extra = NULL;
 
 		if ((1 << queue->meta[npo.meta_cons].gso_type) &
-		    queue->vif->gso_prefix_mask) {
+		    vif->gso_prefix_mask) {
 			resp = RING_GET_RESPONSE(&queue->rx,
 						 queue->rx.rsp_prod_pvt++);
 
@@ -610,7 +628,7 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
 		queue->stats.tx_bytes += skb->len;
 		queue->stats.tx_packets++;
 
-		status = xenvif_check_gop(queue->vif,
+		status = xenvif_check_gop(vif,
 					  XENVIF_RX_CB(skb)->meta_slots_used,
 					  &npo);
 
@@ -632,21 +650,57 @@ static void xenvif_rx_action(struct xenvif_queue *queue)
 					flags);
 
 		if ((1 << queue->meta[npo.meta_cons].gso_type) &
-		    queue->vif->gso_mask) {
-			struct xen_netif_extra_info *gso =
-				(struct xen_netif_extra_info *)
+		    vif->gso_mask) {
+			extra = (struct xen_netif_extra_info *)
 				RING_GET_RESPONSE(&queue->rx,
 						  queue->rx.rsp_prod_pvt++);
 
 			resp->flags |= XEN_NETRXF_extra_info;
 
-			gso->u.gso.type = queue->meta[npo.meta_cons].gso_type;
-			gso->u.gso.size = queue->meta[npo.meta_cons].gso_size;
-			gso->u.gso.pad = 0;
-			gso->u.gso.features = 0;
+			extra->u.gso.type = queue->meta[npo.meta_cons].gso_type;
+			extra->u.gso.size = queue->meta[npo.meta_cons].gso_size;
+			extra->u.gso.pad = 0;
+			extra->u.gso.features = 0;
+
+			extra->type = XEN_NETIF_EXTRA_TYPE_GSO;
+			extra->flags = 0;
+		}
+
+		if (skb->sw_hash) {
+			/* Since the skb got here via xenvif_select_queue()
+			 * we know that the hash has been re-calculated
+			 * according to a configuration set by the frontend
+			 * and therefore we know that it is legitimate to
+			 * pass it to the frontend.
+			 */
+			if (resp->flags & XEN_NETRXF_extra_info)
+				extra->flags |= XEN_NETIF_EXTRA_FLAG_MORE;
+			else
+				resp->flags |= XEN_NETRXF_extra_info;
+
+			extra = (struct xen_netif_extra_info *)
+				RING_GET_RESPONSE(&queue->rx,
+						  queue->rx.rsp_prod_pvt++);
+
+			extra->u.hash.algorithm =
+				XEN_NETIF_CTRL_HASH_ALGORITHM_TOEPLITZ;
+
+			if (skb->l4_hash)
+				extra->u.hash.type =
+					skb->protocol == htons(ETH_P_IP) ?
+					_XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP :
+					_XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP;
+			else
+				extra->u.hash.type =
+					skb->protocol == htons(ETH_P_IP) ?
+					_XEN_NETIF_CTRL_HASH_TYPE_IPV4 :
+					_XEN_NETIF_CTRL_HASH_TYPE_IPV6;
+
+			*(uint32_t *)extra->u.hash.value =
+				skb_get_hash_raw(skb);
 
-			gso->type = XEN_NETIF_EXTRA_TYPE_GSO;
-			gso->flags = 0;
+			extra->type = XEN_NETIF_EXTRA_TYPE_HASH;
+			extra->flags = 0;
 		}
 
 		xenvif_add_frag_responses(queue, status,