On Thu, Aug 09, 2018 at 01:34:55PM -0500, Allain Legacy wrote:
From: eric zhang <eric.zh...@windriver.com>

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.

Signed-off-by: eric zhang <eric.zh...@windriver.com>
Signed-off-by: Allain Legacy <allain.leg...@windriver.com>
---
drivers/net/virtio/virtio_user/vhost_kernel.c     |  2 +-
drivers/net/virtio/virtio_user/vhost_kernel_tap.c | 56 +++++++++++++++++------
drivers/net/virtio/virtio_user/vhost_kernel_tap.h |  2 +-
3 files changed, 44 insertions(+), 16 deletions(-)

diff --git a/drivers/net/virtio/virtio_user/vhost_kernel.c 
b/drivers/net/virtio/virtio_user/vhost_kernel.c
index b2444096c..66f2eaca9 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel.c
@@ -339,7 +339,7 @@ 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;
diff --git a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c 
b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
index 9ea7ade74..eda9fb78c 100644
--- a/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
+++ b/drivers/net/virtio/virtio_user/vhost_kernel_tap.c
@@ -16,21 +16,54 @@

#include "vhost_kernel_tap.h"
#include "../virtio_logs.h"
+#include "../virtio_pci.h"
+
+static int
+vhost_kernel_tap_set_offload(int fd, uint64_t feature)
+{
+       unsigned int offload = 0;
+
+       if (feature & (1ULL << VIRTIO_NET_F_GUEST_CSUM))
+               offload |= TUN_F_CSUM;
+       if (feature & (1ULL << VIRTIO_NET_F_GUEST_TSO4))
+               offload |= TUN_F_TSO4;
+       if (feature & (1ULL << VIRTIO_NET_F_GUEST_TSO6))
+               offload |= TUN_F_TSO6;
+       if (feature & ((1ULL << VIRTIO_NET_F_GUEST_TSO4) |
+               (1ULL << VIRTIO_NET_F_GUEST_TSO6)) &&
+               (feature & (1ULL << VIRTIO_NET_F_GUEST_ECN)))
+               offload |= TUN_F_TSO_ECN;
+       if (feature & (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 +123,8 @@ 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));
+       if (vhost_kernel_tap_set_offload(tapfd, features) != 0)

Since we only check for != 0 we could just have it return a bool.
But it is just a nit.

Reviewed-by: Jens Freimann <jfreim...@redhat.com>
regards,
Jens

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