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, 5 insertions, 10 deletions

diff --git a/arch/um/os-Linux/drivers/tuntap_kern.c b/arch/um/os-Linux/drivers/tuntap_kern.c
index 9ade1f892ac..9d384807b07 100644
--- a/arch/um/os-Linux/drivers/tuntap_kern.c
+++ b/arch/um/os-Linux/drivers/tuntap_kern.c
@@ -35,20 +35,15 @@ static void tuntap_init(struct net_device *dev, void *data)
 	printk("\n");
 }
 
-static int tuntap_read(int fd, struct sk_buff **skb,
-		       struct uml_net_private *lp)
+static int tuntap_read(int fd, struct sk_buff *skb, struct uml_net_private *lp)
 {
-	*skb = ether_adjust_skb(*skb, ETH_HEADER_OTHER);
-	if (*skb == NULL)
-		return -ENOMEM;
-	return net_read(fd, skb_mac_header(*skb),
-			(*skb)->dev->mtu + ETH_HEADER_OTHER);
+	return net_read(fd, skb_mac_header(skb),
+			skb->dev->mtu + ETH_HEADER_OTHER);
 }
 
-static int tuntap_write(int fd, struct sk_buff **skb,
-			struct uml_net_private *lp)
+static int tuntap_write(int fd, struct sk_buff *skb, struct uml_net_private *lp)
 {
-	return net_write(fd, (*skb)->data, (*skb)->len);
+	return net_write(fd, skb->data, skb->len);
 }
 
 const struct net_kern_info tuntap_kern_info = {