uml: network driver MTU cleanups

A bunch of MTU-related cleanups in the network code.

First, there is the addition of the notion of a maximally-sized packet, which
is the MTU plus headers.  This is used to size the skb that will receive a
packet.  This allows ether_adjust_skb to go away, as it was used to resize the
skb after it was allocated.

Since the skb passed into the low-level read routine is no longer resized, and
possibly reallocated, there, they (and the write routines) don't need to get
an sk_buff **.  They just need the sk_buff * now.  The callers of
ether_adjust_skb still need to do the skb_put, so that's now inlined.

The MAX_PACKET definitions in most of the drivers are gone.

The set_mtu methods were all the same and did nothing, so they can be
removed.

The ethertap driver had a typo which doubled the size of the packet rather
than adding two bytes to it.  It also wasn't defining its setup_size, causing
a zero-byte kmalloc and crash when the invalid pointer returned from kmalloc
was dereferenced.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 9 deletions

diff --git a/arch/um/os-Linux/drivers/tuntap_user.c b/arch/um/os-Linux/drivers/tuntap_user.c
index 10714a413cfd..6c55d3c8ead8 100644
--- a/arch/um/os-Linux/drivers/tuntap_user.c
+++ b/arch/um/os-Linux/drivers/tuntap_user.c
@@ -18,8 +18,6 @@
 #include "tuntap.h"
 #include "user.h"
 
-#define MAX_PACKET ETH_MAX_PACKET
-
 static int tuntap_user_init(void *data, void *dev)
 {
         struct tuntap_data *pri = data;
@@ -206,18 +204,13 @@ static void tuntap_close(int fd, void *data)
         pri->fd = -1;
 }
 
-static int tuntap_set_mtu(int mtu, void *data)
-{
-        return mtu;
-}
-
 const struct net_user_info tuntap_user_info = {
         .init           = tuntap_user_init,
         .open           = tuntap_open,
         .close          = tuntap_close,
         .remove         = NULL,
-        .set_mtu        = tuntap_set_mtu,
         .add_address    = tuntap_add_addr,
         .delete_address = tuntap_del_addr,
-        .max_packet     = MAX_PACKET
+        .mtu            = ETH_MAX_PACKET,
+        .max_packet     = ETH_MAX_PACKET + ETH_HEADER_OTHER,
 };