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, 7 deletions

diff --git a/arch/um/os-Linux/drivers/ethertap_user.c b/arch/um/os-Linux/drivers/ethertap_user.c
index 29404b955f1..4ff55360344 100644
--- a/arch/um/os-Linux/drivers/ethertap_user.c
+++ b/arch/um/os-Linux/drivers/ethertap_user.c
@@ -222,11 +222,6 @@ static void etap_close(int fd, void *data)
         pri->control_fd = -1;
 }
 
-static int etap_set_mtu(int mtu, void *data)
-{
-        return mtu;
-}
-
 static void etap_add_addr(unsigned char *addr, unsigned char *netmask,
                           void *data)
 {
@@ -254,8 +249,8 @@ const struct net_user_info ethertap_user_info = {
         .open           = etap_open,
         .close          = etap_close,
         .remove         = NULL,
-        .set_mtu        = etap_set_mtu,
         .add_address    = etap_add_addr,
         .delete_address = etap_del_addr,
-        .max_packet     = MAX_PACKET - ETH_HEADER_ETHERTAP
+        .mtu            = ETH_MAX_PACKET,
+        .max_packet     = ETH_MAX_PACKET + ETH_HEADER_ETHERTAP,
 };