[2/6] [TUN]: Add GSO detection

[Herbert Xu]

This is Rusty's second patch to tun to allow user-space access
to the GSO feature in a backwards compatible way.

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 34a03ec..4c15dc4 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -800,6 +800,15 @@ static int tun_chr_ioctl(struct inode *inode, struct file *file,
 		return 0;
 	}
 
+	if (cmd == TUNGETFEATURES) {
+		/* Currently this just means: "what IFF flags are valid?".
+		 * This is needed because we never checked for invalid flags on
+		 * TUNSETIFF.  This was introduced with IFF_GSO_HDR, so if a
+		 * kernel doesn't have this ioctl, it doesn't have GSO header
+		 * support. */
+		return put_user(IFF_ALL_FLAGS, (unsigned int __user*)argp);
+	}
+
 	if (!tun)
 		return -EBADFD;
 
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
index 3dbef10..fe6855d 100644
--- a/include/linux/if_tun.h
+++ b/include/linux/if_tun.h
@@ -84,6 +84,7 @@ struct tun_struct {
 #define TUNSETOWNER   _IOW('T', 204, int)
 #define TUNSETLINK    _IOW('T', 205, int)
 #define TUNSETGROUP   _IOW('T', 206, int)
+#define TUNGETFEATURES _IOR('T', 207, unsigned int)
 
 /* TUNSETIFF ifr flags */
 #define IFF_TUN		0x0001
@@ -93,6 +94,8 @@ struct tun_struct {
 #define IFF_VIRTIO_HDR	0x4000
 #define IFF_RECV_CSUM	0x8000
 #define IFF_RECV_GSO	0x0800
+#define IFF_ALL_FLAGS (IFF_TUN | IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE | \
+		       IFF_VIRTIO_HDR | IFF_RECV_CSUM | IFF_RECV_GSO)
 
 struct tun_pi {
 	unsigned short flags;
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert at gondor.apana.org.au>
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