The problem with introducing checksum offload and gso to tun is 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 new IFF_ flags.
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
#include
#include
#include
#include
#include
#include
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" },
};
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 |8
include/linux/if_tun.h |1 +
2 files changed, 9 insertions(+)
diff -r 8414a579e106 drivers/net/tun.c
--- a/drivers/net/tun.c Tue Apr 22 07:36:45 2008 +1000
+++ b/drivers/net/tun.c Tue Apr 22 07:37:33 2008 +1000
@@ -625,6 +625,14 @@ 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. */
+ return put_user(IFF_TUN | IFF_TAP | IFF_NO_PI | IFF_ONE_QUEUE,
+ (unsigned int __user*)argp);
+ }
+
if (!tun)
return -EBADFD;
diff -r 8414a579e106 include/linux/if_tun.h
--- a/include/linux/if_tun.hTue Apr 22 07:36:45 2008 +1000
+++ b/include/linux/if_tun.hTue Apr 22 07:37:33 2008 +1000
@@ -42,6 +42,7 @@
#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_TUN0x0001
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