tun: TUNSETFEATURES to set gso features.

ethtool is useful for setting (some) device fields, but it's
root-only.  Finer feature control is available through a tun-specific
ioctl.

(Includes Mark McLoughlin <markmc@redhat.com>'s fix to hold rtnl sem).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Max Krasnyansky <maxk@qualcomm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 56 insertions, 0 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 3bb991fd2b51..a314955e6994 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -611,6 +611,46 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
         return err;
 }
 
+/* This is like a cut-down ethtool ops, except done via tun fd so no
+ * privs required. */
+static int set_offload(struct net_device *dev, unsigned long arg)
+{
+        unsigned int old_features, features;
+
+        old_features = dev->features;
+        /* Unset features, set them as we chew on the arg. */
+        features = (old_features & ~(NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST
+                                    |NETIF_F_TSO_ECN|NETIF_F_TSO|NETIF_F_TSO6));
+
+        if (arg & TUN_F_CSUM) {
+                features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
+                arg &= ~TUN_F_CSUM;
+
+                if (arg & (TUN_F_TSO4|TUN_F_TSO6)) {
+                        if (arg & TUN_F_TSO_ECN) {
+                                features |= NETIF_F_TSO_ECN;
+                                arg &= ~TUN_F_TSO_ECN;
+                        }
+                        if (arg & TUN_F_TSO4)
+                                features |= NETIF_F_TSO;
+                        if (arg & TUN_F_TSO6)
+                                features |= NETIF_F_TSO6;
+                        arg &= ~(TUN_F_TSO4|TUN_F_TSO6);
+                }
+        }
+
+        /* This gives the user a way to test for new features in future by
+         * trying to set them. */
+        if (arg)
+                return -EINVAL;
+
+        dev->features = features;
+        if (old_features != dev->features)
+                netdev_features_change(dev);
+
+        return 0;
+}
+
 static int tun_chr_ioctl(struct inode *inode, struct file *file,
                          unsigned int cmd, unsigned long arg)
 {
@@ -715,6 +755,15 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file,
                 break;
 #endif
 
+        case TUNSETOFFLOAD:
+        {
+                int ret;
+                rtnl_lock();
+                ret = set_offload(tun->dev, arg);
+                rtnl_unlock();
+                return ret;
+        }
+
         case SIOCGIFFLAGS:
                 ifr.ifr_flags = tun->if_flags;
                 if (copy_to_user( argp, &ifr, sizeof ifr))
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
index 94f76a112303..3f0a0995d449 100644
--- a/include/linux/if_tun.h
+++ b/include/linux/if_tun.h
@@ -41,6 +41,7 @@
 #define TUNSETLINK    _IOW('T', 205, int)
 #define TUNSETGROUP   _IOW('T', 206, int)
 #define TUNGETFEATURES _IOR('T', 207, unsigned int)
+#define TUNSETOFFLOAD _IOW('T', 208, unsigned int)
 
 /* TUNSETIFF ifr flags */
 #define IFF_TUN         0x0001
@@ -48,6 +49,12 @@
 #define IFF_NO_PI       0x1000
 #define IFF_ONE_QUEUE   0x2000
 
+/* Features for GSO (TUNSETOFFLOAD). */
+#define TUN_F_CSUM      0x01    /* You can hand me unchecksummed packets. */
+#define TUN_F_TSO4      0x02    /* I can handle TSO for IPv4 packets */
+#define TUN_F_TSO6      0x04    /* I can handle TSO for IPv6 packets */
+#define TUN_F_TSO_ECN   0x08    /* I can handle TSO with ECN bits. */
+
 struct tun_pi {
         unsigned short flags;
         __be16 proto;