net/virtio-user: check negotiated features before set

This patch checks negotiated features to see if necessary to offload
before set the tap device offload capabilities. It also checks if kernel
support the TUNSETOFFLOAD operation.

Fixes: 5e97e42025 ("net/virtio-user: enable offloading")
Cc: stable@dpdk.org

Signed-off-by: Eric Zhang <eric.zhang@windriver.com>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>

drivers/net/virtio/virtio_user/vhost_kernel.c

@@ -147,8 +147,8 @@ prepare_vhost_memory_kernel(void)
 	 (1ULL << VIRTIO_NET_F_HOST_TSO6) |	\
 	 (1ULL << VIRTIO_NET_F_CSUM))
 
-static int
-tap_supporte_mq(void)
+static unsigned int
+tap_support_features(void)
 {
 	int tapfd;
 	unsigned int tap_features;
@@ -167,7 +167,7 @@ tap_supporte_mq(void)
 	}
 
 	close(tapfd);
-	return tap_features & IFF_MULTI_QUEUE;
+	return tap_features;
 }
 
 static int
@@ -181,6 +181,7 @@ vhost_kernel_ioctl(struct virtio_user_dev *dev,
 	struct vhost_memory_kernel *vm = NULL;
 	int vhostfd;
 	unsigned int queue_sel;
+	unsigned int features;
 
 	PMD_DRV_LOG(INFO, "%s", vhost_msg_strings[req]);
 
@@ -234,17 +235,20 @@ vhost_kernel_ioctl(struct virtio_user_dev *dev,
 	}
 
 	if (!ret && req_kernel == VHOST_GET_FEATURES) {
+		features = tap_support_features();
 		/* with tap as the backend, all these features are supported
 		 * but not claimed by vhost-net, so we add them back when
 		 * reporting to upper layer.
 		 */
-		*((uint64_t *)arg) |= VHOST_KERNEL_GUEST_OFFLOADS_MASK;
-		*((uint64_t *)arg) |= VHOST_KERNEL_HOST_OFFLOADS_MASK;
+		if (features & IFF_VNET_HDR) {
+			*((uint64_t *)arg) |= VHOST_KERNEL_GUEST_OFFLOADS_MASK;
+			*((uint64_t *)arg) |= VHOST_KERNEL_HOST_OFFLOADS_MASK;
+		}
 
 		/* vhost_kernel will not declare this feature, but it does
 		 * support multi-queue.
 		 */
-		if (tap_supporte_mq())
+		if (features & IFF_MULTI_QUEUE)
 			*(uint64_t *)arg |= (1ull << VIRTIO_NET_F_MQ);
 	}
 
@@ -339,7 +343,7 @@ vhost_kernel_enable_queue_pair(struct virtio_user_dev *dev,
 		hdr_size = sizeof(struct virtio_net_hdr);
 
 	tapfd = vhost_kernel_open_tap(&dev->ifname, hdr_size, req_mq,
-			 (char *)dev->mac_addr);
+			 (char *)dev->mac_addr, dev->features);
 	if (tapfd < 0) {
 		PMD_DRV_LOG(ERR, "fail to open tap for vhost kernel");
 		return -1;

drivers/net/virtio/virtio_user/vhost_kernel_tap.c

@@ -16,21 +16,55 @@
 
 #include "vhost_kernel_tap.h"
 #include "../virtio_logs.h"
+#include "../virtio_pci.h"
+
+static int
+vhost_kernel_tap_set_offload(int fd, uint64_t features)
+{
+	unsigned int offload = 0;
+
+	if (features & (1ULL << VIRTIO_NET_F_GUEST_CSUM)) {
+		offload |= TUN_F_CSUM;
+		if (features & (1ULL << VIRTIO_NET_F_GUEST_TSO4))
+			offload |= TUN_F_TSO4;
+		if (features & (1ULL << VIRTIO_NET_F_GUEST_TSO6))
+			offload |= TUN_F_TSO6;
+		if (features & ((1ULL << VIRTIO_NET_F_GUEST_TSO4) |
+			(1ULL << VIRTIO_NET_F_GUEST_TSO6)) &&
+			(features & (1ULL << VIRTIO_NET_F_GUEST_ECN)))
+			offload |= TUN_F_TSO_ECN;
+		if (features & (1ULL << VIRTIO_NET_F_GUEST_UFO))
+			offload |= TUN_F_UFO;
+	}
+
+	if (offload != 0) {
+		/* Check if our kernel supports TUNSETOFFLOAD */
+		if (ioctl(fd, TUNSETOFFLOAD, 0) != 0 && errno == EINVAL) {
+			PMD_DRV_LOG(ERR, "Kernel does't support TUNSETOFFLOAD\n");
+			return -ENOTSUP;
+		}
+
+		if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
+			offload &= ~TUN_F_UFO;
+			if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
+				PMD_DRV_LOG(ERR, "TUNSETOFFLOAD ioctl() failed: %s\n",
+					strerror(errno));
+				return -1;
+			}
+		}
+	}
+
+	return 0;
+}
 
 int
 vhost_kernel_open_tap(char **p_ifname, int hdr_size, int req_mq,
-			 const char *mac)
+			 const char *mac, uint64_t features)
 {
 	unsigned int tap_features;
 	int sndbuf = INT_MAX;
 	struct ifreq ifr;
 	int tapfd;
-	unsigned int offload =
-			TUN_F_CSUM |
-			TUN_F_TSO4 |
-			TUN_F_TSO6 |
-			TUN_F_TSO_ECN |
-			TUN_F_UFO;
 
 	/* TODO:
 	 * 1. verify we can get/set vnet_hdr_len, tap_probe_vnet_hdr_len
@@ -90,13 +124,7 @@ vhost_kernel_open_tap(char **p_ifname, int hdr_size, int req_mq,
 		goto error;
 	}
 
-	/* TODO: before set the offload capabilities, we'd better (1) check
-	 * negotiated features to see if necessary to offload; (2) query tap
-	 * to see if it supports the offload capabilities.
-	 */
-	if (ioctl(tapfd, TUNSETOFFLOAD, offload) != 0)
-		PMD_DRV_LOG(ERR, "TUNSETOFFLOAD ioctl() failed: %s",
-			   strerror(errno));
+	vhost_kernel_tap_set_offload(tapfd, features);
 
 	memset(&ifr, 0, sizeof(ifr));
 	ifr.ifr_hwaddr.sa_family = ARPHRD_ETHER;

drivers/net/virtio/virtio_user/vhost_kernel_tap.h

@@ -36,4 +36,4 @@
 #define PATH_NET_TUN	"/dev/net/tun"
 
 int vhost_kernel_open_tap(char **p_ifname, int hdr_size, int req_mq,
-			 const char *mac);
+			 const char *mac, uint64_t features);