From d9d52b5178af586d679c1052fb161ee05ea2e83f Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Wed, 17 Mar 2010 17:45:01 +0200 Subject: tun: add ioctl to modify vnet header size virtio added mergeable buffers mode where 2 bytes of extra info is put after vnet header but before actual data (tun does not need this data). In hindsight, it would have been better to add the new info *before* the packet: as it is, users need a lot of tricky code to skip the extra 2 bytes in the middle of the iovec, and in fact applications seem to get it wrong, and only work with specific iovec layout. The fact we might need to split iovec also means we might in theory overflow iovec max size. This patch adds a simpler way for applications to handle this, and future proofs the interface against further extensions, by making the size of the virtio net header configurable from userspace. As a result, tun driver will simply skip the extra 2 bytes on both input and output. Signed-off-by: Michael S. Tsirkin Acked-by: David S. Miller --- include/linux/if_tun.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/if_tun.h') diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h index 1350a24..06b1829 100644 --- a/include/linux/if_tun.h +++ b/include/linux/if_tun.h @@ -51,6 +51,8 @@ #define TUNSETSNDBUF _IOW('T', 212, int) #define TUNATTACHFILTER _IOW('T', 213, struct sock_fprog) #define TUNDETACHFILTER _IOW('T', 214, struct sock_fprog) +#define TUNGETVNETHDRSZ _IOR('T', 215, int) +#define TUNSETVNETHDRSZ _IOW('T', 216, int) /* TUNSETIFF ifr flags */ #define IFF_TUN 0x0001 -- cgit v1.1