(No real change, just updated with new bits)
The problem with introducing IFF_RECV_CSUM and IFF_RECV_GSO is that
they need to set dev->features to enable GSO and/or checksumming,
which is supposed to be done before register_netdevice(), ie. as part
of TUNSETIFF.
Unfortunately, TUNSETIFF has always just ignored flags it doesn't understand,
so there's no good way of detecting whether the kernel supports IFF_GSO_HDR.
This patch implements a TUNGETFEATURES ioctl which returns all the valid IFF
flags. It could be extended later to include other features.
Here's an example program which uses it:
#include <linux/if_tun.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <err.h>
#include <stdio.h>
static struct {
unsigned int flag;
const char *name;
} known_flags[] = {
{ IFF_TUN, "TUN" },
{ IFF_TAP, "TAP" },
{ IFF_NO_PI, "NO_PI" },
{ IFF_ONE_QUEUE, "ONE_QUEUE" },
{ IFF_VIRTIO_HDR, "VIRTIO_HDR" },
{ IFF_RECV_CSUM, "RECV_CSUM" },
{ IFF_RECV_GSO, "RECV_GSO" },
};
int main()
{
unsigned int features, i;
int netfd = open("/dev/net/tun", O_RDWR);
if (netfd < 0)
err(1, "Opening /dev/net/tun");
if (ioctl(netfd, TUNGETFEATURES, &features) != 0) {
printf("Kernel does not support TUNGETFEATURES, guessing\n");
features = (IFF_TUN|IFF_TAP|IFF_NO_PI|IFF_ONE_QUEUE);
}
printf("Available features are: ");
for (i = 0; i < sizeof(known_flags)/sizeof(known_flags[0]); i++) {
if (features & known_flags[i].flag) {
features &= ~known_flags[i].flag;
printf("%s ", known_flags[i].name);
}
}
if (features)
printf("(UNKNOWN %#x)", features);
printf("\n");
return 0;
}
Signed-off-by: Rusty Russell <[EMAIL PROTECTED]>
---
drivers/net/tun.c | 9 +++++++++
include/linux/if_tun.h | 3 +++
2 files changed, 12 insertions(+)
diff -r c0e7a8b99325 drivers/net/tun.c
--- a/drivers/net/tun.c Wed Jan 23 20:12:51 2008 +1100
+++ b/drivers/net/tun.c Wed Jan 23 20:17:28 2008 +1100
@@ -790,6 +790,15 @@ static int tun_chr_ioctl(struct inode *i
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 -r c0e7a8b99325 include/linux/if_tun.h
--- a/include/linux/if_tun.h Wed Jan 23 20:12:51 2008 +1100
+++ b/include/linux/if_tun.h Wed Jan 23 20:17:28 2008 +1100
@@ -82,6 +82,7 @@ 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
@@ -91,6 +92,8 @@ 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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