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, 8 insertions, 34 deletions

diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index b097a24c1496..59811cc880e0 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -41,16 +41,16 @@ static int uml_net_rx(struct net_device *dev)
         struct sk_buff *skb;
 
         /* If we can't allocate memory, try again next round. */
-        skb = dev_alloc_skb(dev->mtu);
+        skb = dev_alloc_skb(lp->max_packet);
         if (skb == NULL) {
                 lp->stats.rx_dropped++;
                 return 0;
         }
 
         skb->dev = dev;
-        skb_put(skb, dev->mtu);
+        skb_put(skb, lp->max_packet);
         skb_reset_mac_header(skb);
-        pkt_len = (*lp->read)(lp->fd, &skb, lp);
+        pkt_len = (*lp->read)(lp->fd, skb, lp);
 
         if (pkt_len > 0) {
                 skb_trim(skb, pkt_len);
@@ -178,7 +178,7 @@ static int uml_net_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
         spin_lock_irqsave(&lp->lock, flags);
 
-        len = (*lp->write)(lp->fd, &skb, lp);
+        len = (*lp->write)(lp->fd, skb, lp);
 
         if (len == skb->len) {
                 lp->stats.tx_packets++;
@@ -240,22 +240,9 @@ static int uml_net_set_mac(struct net_device *dev, void *addr)
 
 static int uml_net_change_mtu(struct net_device *dev, int new_mtu)
 {
-        struct uml_net_private *lp = dev->priv;
-        int err = 0;
-
-        spin_lock_irq(&lp->lock);
-
-        new_mtu = (*lp->set_mtu)(new_mtu, &lp->user);
-        if (new_mtu < 0) {
-                err = new_mtu;
-                goto out;
-        }
-
         dev->mtu = new_mtu;
 
- out:
-        spin_unlock_irq(&lp->lock);
-        return err;
+        return 0;
 }
 
 static void uml_net_get_drvinfo(struct net_device *dev,
@@ -427,6 +414,7 @@ static void eth_configure(int n, void *init, char *mac,
                   .dev                  = dev,
                   .fd                   = -1,
                   .mac                  = { 0xfe, 0xfd, 0x0, 0x0, 0x0, 0x0},
+                  .max_packet           = transport->user->max_packet,
                   .protocol             = transport->kern->protocol,
                   .open                 = transport->user->open,
                   .close                = transport->user->close,
@@ -434,8 +422,7 @@ static void eth_configure(int n, void *init, char *mac,
                   .read                 = transport->kern->read,
                   .write                = transport->kern->write,
                   .add_address          = transport->user->add_address,
-                  .delete_address       = transport->user->delete_address,
-                  .set_mtu              = transport->user->set_mtu });
+                  .delete_address       = transport->user->delete_address });
 
         init_timer(&lp->tl);
         spin_lock_init(&lp->lock);
@@ -447,7 +434,7 @@ static void eth_configure(int n, void *init, char *mac,
                 goto out_unregister;
 
         set_ether_mac(dev, device->mac);
-        dev->mtu = transport->user->max_packet;
+        dev->mtu = transport->user->mtu;
         dev->open = uml_net_open;
         dev->hard_start_xmit = uml_net_start_xmit;
         dev->stop = uml_net_close;
@@ -807,19 +794,6 @@ static void close_devices(void)
 
 __uml_exitcall(close_devices);
 
-struct sk_buff *ether_adjust_skb(struct sk_buff *skb, int extra)
-{
-        if ((skb != NULL) && (skb_tailroom(skb) < extra)) {
-                struct sk_buff *skb2;
-
-                skb2 = skb_copy_expand(skb, 0, extra, GFP_ATOMIC);
-                dev_kfree_skb(skb);
-                skb = skb2;
-        }
-        if (skb != NULL) skb_put(skb, extra);
-        return skb;
-}
-
 void iter_addresses(void *d, void (*cb)(unsigned char *, unsigned char *,
                                         void *),
                     void *arg)