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authorRusty Russell <rusty@rustcorp.com.au>2008-07-03 03:45:32 -0700
committerDavid S. Miller <davem@davemloft.net>2008-07-03 03:45:32 -0700
commit07240fd0902c872f044f523893364a1a24c9f278 (patch)
tree096286005c0b1a19c23011b3c7418710704b833e /include/linux/if_tun.h
parent44d28ab19c64d095314ac66f765d0c747519f4ed (diff)
tun: Interface to query tun/tap features.
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 <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" }, }; 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 <rusty@rustcorp.com.au> Acked-by: Max Krasnyansky <maxk@qualcomm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/if_tun.h')
-rw-r--r--include/linux/if_tun.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
index 18f31b6187a..94f76a11230 100644
--- a/include/linux/if_tun.h
+++ b/include/linux/if_tun.h
@@ -40,6 +40,7 @@
#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_TUN 0x0001