lguest: Use GSO/IFF_VNET_HDR extensions on tun/tap

Guest -> Host 1GB TCP:
Before 20.1974 seconds xmit 214510 recv 5 timeout 214491 usec 278
After 8.43625 seconds xmit 95640 recv 198266 timeout 49771 usec 1252

Host -> Guest 1GB TCP:
Before: Seconds 9.98854 xmit 172166 recv 5344 timeout 172157 usec 251
After: Seconds 5.72803 xmit 244322 recv 9919 timeout 244302 usec 156

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 20 insertions, 14 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 0d1b0265d8e2..dc49f50e04ac 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -929,11 +929,9 @@ static void handle_net_output(int fd, struct virtqueue *vq, bool timeout)
         while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
                 if (in)
                         errx(1, "Input buffers in output queue?");
-                /* Check header, but otherwise ignore it (we told the Guest we
-                 * supported no features, so it shouldn't have anything
-                 * interesting). */
-                (void)convert(&iov[0], struct virtio_net_hdr);
-                len = writev(vq->dev->fd, iov+1, out-1);
+                len = writev(vq->dev->fd, iov, out);
+                if (len < 0)
+                        err(1, "Writing network packet to tun");
                 add_used_and_trigger(fd, vq, head, len);
                 num++;
         }
@@ -958,7 +956,6 @@ static bool handle_tun_input(int fd, struct device *dev)
         unsigned int head, in_num, out_num;
         int len;
         struct iovec iov[dev->vq->vring.num];
-        struct virtio_net_hdr *hdr;
 
         /* First we need a network buffer from the Guests's recv virtqueue. */
         head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
@@ -977,18 +974,13 @@ static bool handle_tun_input(int fd, struct device *dev)
         } else if (out_num)
                 errx(1, "Output buffers in network recv queue?");
 
-        /* First element is the header: we set it to 0 (no features). */
-        hdr = convert(&iov[0], struct virtio_net_hdr);
-        hdr->flags = 0;
-        hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
-
         /* Read the packet from the device directly into the Guest's buffer. */
-        len = readv(dev->fd, iov+1, in_num-1);
+        len = readv(dev->fd, iov, in_num);
         if (len <= 0)
                 err(1, "reading network");
 
         /* Tell the Guest about the new packet. */
-        add_used_and_trigger(fd, dev->vq, head, sizeof(*hdr) + len);
+        add_used_and_trigger(fd, dev->vq, head, len);
 
         verbose("tun input packet len %i [%02x %02x] (%s)\n", len,
                 ((u8 *)iov[1].iov_base)[0], ((u8 *)iov[1].iov_base)[1],
@@ -1490,11 +1482,15 @@ static int get_tun_device(char tapif[IFNAMSIZ])
          * the truth, I completely blundered my way through this code, but it
          * works now! */
         netfd = open_or_die("/dev/net/tun", O_RDWR);
-        ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
+        ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
         strcpy(ifr.ifr_name, "tap%d");
         if (ioctl(netfd, TUNSETIFF, &ifr) != 0)
                 err(1, "configuring /dev/net/tun");
 
+        if (ioctl(netfd, TUNSETOFFLOAD,
+                  TUN_F_CSUM|TUN_F_TSO4|TUN_F_TSO6|TUN_F_TSO_ECN) != 0)
+                err(1, "Could not set features for tun device");
+
         /* We don't need checksums calculated for packets coming in this
          * device: trust us! */
         ioctl(netfd, TUNSETNOCSUM, 1);
@@ -1561,6 +1557,16 @@ static void setup_tun_net(char *arg)
         /* Tell Guest what MAC address to use. */
         add_feature(dev, VIRTIO_NET_F_MAC);
         add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
+        /* Expect Guest to handle everything except UFO */
+        add_feature(dev, VIRTIO_NET_F_CSUM);
+        add_feature(dev, VIRTIO_NET_F_GUEST_CSUM);
+        add_feature(dev, VIRTIO_NET_F_MAC);
+        add_feature(dev, VIRTIO_NET_F_GUEST_TSO4);
+        add_feature(dev, VIRTIO_NET_F_GUEST_TSO6);
+        add_feature(dev, VIRTIO_NET_F_GUEST_ECN);
+        add_feature(dev, VIRTIO_NET_F_HOST_TSO4);
+        add_feature(dev, VIRTIO_NET_F_HOST_TSO6);
+        add_feature(dev, VIRTIO_NET_F_HOST_ECN);
         set_config(dev, sizeof(conf), &conf);
 
         /* We don't need the socket any more; setup is done. */