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[NET]: Avoid allocating skb in skb_pad
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First of all it is unnecessary to allocate a new skb in skb_pad since
the existing one is not shared.  More importantly, our hard_start_xmit
interface does not allow a new skb to be allocated since that breaks
requeueing.

This patch uses pskb_expand_head to expand the existing skb and linearize
it if needed.  Actually, someone should sift through every instance of
skb_pad on a non-linear skb as they do not fit the reasons why this was
originally created.

Incidentally, this fixes a minor bug when the skb is cloned (tcpdump,
TCP, etc.).  As it is skb_pad will simply write over a cloned skb.  Because
of the position of the write it is unlikely to cause problems but still
it's best if we don't do it.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
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@herbertx @davem330
herbertx authored and davem330 committed Jun 23, 2006
1 parent 5fa21d8 commit 5b057c6
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Showing 36 changed files with 74 additions and 103 deletions.
3 changes: 1 addition & 2 deletions drivers/net/3c527.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1031,8 +1031,7 @@ static int mc32_send_packet(struct sk_buff *skb, struct net_device *dev)
return 1;
}

skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL) {
if (skb_padto(skb, ETH_ZLEN)) {
netif_wake_queue(dev);
return 0;
}
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3 changes: 1 addition & 2 deletions drivers/net/82596.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1070,8 +1070,7 @@ static int i596_start_xmit(struct sk_buff *skb, struct net_device *dev)
skb->len, (unsigned int)skb->data));

if (skb->len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/a2065.c
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Original file line number Diff line number Diff line change
Expand Up @@ -573,8 +573,7 @@ static int lance_start_xmit (struct sk_buff *skb, struct net_device *dev)

if (len < ETH_ZLEN) {
len = ETH_ZLEN;
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
}

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3 changes: 1 addition & 2 deletions drivers/net/ariadne.c
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Original file line number Diff line number Diff line change
Expand Up @@ -607,8 +607,7 @@ static int ariadne_start_xmit(struct sk_buff *skb, struct net_device *dev)
/* FIXME: is the 79C960 new enough to do its own padding right ? */
if (skb->len < ETH_ZLEN)
{
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
len = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/arm/ether1.c
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Original file line number Diff line number Diff line change
Expand Up @@ -700,8 +700,7 @@ ether1_sendpacket (struct sk_buff *skb, struct net_device *dev)
}

if (skb->len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
goto out;
}

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3 changes: 1 addition & 2 deletions drivers/net/arm/ether3.c
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Original file line number Diff line number Diff line change
Expand Up @@ -518,8 +518,7 @@ ether3_sendpacket(struct sk_buff *skb, struct net_device *dev)

length = (length + 1) & ~1;
if (length != skb->len) {
skb = skb_padto(skb, length);
if (skb == NULL)
if (skb_padto(skb, length))
goto out;
}

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3 changes: 1 addition & 2 deletions drivers/net/atarilance.c
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Original file line number Diff line number Diff line change
Expand Up @@ -804,8 +804,7 @@ static int lance_start_xmit( struct sk_buff *skb, struct net_device *dev )
++len;

if (len > skb->len) {
skb = skb_padto(skb, len);
if (skb == NULL)
if (skb_padto(skb, len))
return 0;
}

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3 changes: 1 addition & 2 deletions drivers/net/cassini.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2915,8 +2915,7 @@ static int cas_start_xmit(struct sk_buff *skb, struct net_device *dev)
*/
static int ring;

skb = skb_padto(skb, cp->min_frame_size);
if (!skb)
if (skb_padto(skb, cp->min_frame_size))
return 0;

/* XXX: we need some higher-level QoS hooks to steer packets to
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3 changes: 1 addition & 2 deletions drivers/net/declance.c
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Original file line number Diff line number Diff line change
Expand Up @@ -885,8 +885,7 @@ static int lance_start_xmit(struct sk_buff *skb, struct net_device *dev)
len = skblen;

if (len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
len = ETH_ZLEN;
}
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7 changes: 2 additions & 5 deletions drivers/net/depca.c
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Original file line number Diff line number Diff line change
Expand Up @@ -938,11 +938,8 @@ static int depca_start_xmit(struct sk_buff *skb, struct net_device *dev)
if (skb->len < 1)
goto out;

if (skb->len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
goto out;
}
if (skb_padto(skb, ETH_ZLEN))
goto out;

netif_stop_queue(dev);

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3 changes: 1 addition & 2 deletions drivers/net/eepro.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1154,8 +1154,7 @@ static int eepro_send_packet(struct sk_buff *skb, struct net_device *dev)
printk(KERN_DEBUG "%s: entering eepro_send_packet routine.\n", dev->name);

if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/eexpress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -677,8 +677,7 @@ static int eexp_xmit(struct sk_buff *buf, struct net_device *dev)
#endif

if (buf->len < ETH_ZLEN) {
buf = skb_padto(buf, ETH_ZLEN);
if (buf == NULL)
if (skb_padto(buf, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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7 changes: 2 additions & 5 deletions drivers/net/epic100.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1027,11 +1027,8 @@ static int epic_start_xmit(struct sk_buff *skb, struct net_device *dev)
u32 ctrl_word;
unsigned long flags;

if (skb->len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
return 0;
}
if (skb_padto(skb, ETH_ZLEN))
return 0;

/* Caution: the write order is important here, set the field with the
"ownership" bit last. */
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3 changes: 1 addition & 2 deletions drivers/net/eth16i.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1064,8 +1064,7 @@ static int eth16i_tx(struct sk_buff *skb, struct net_device *dev)
unsigned long flags;

if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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7 changes: 2 additions & 5 deletions drivers/net/hp100.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1487,11 +1487,8 @@ static int hp100_start_xmit_bm(struct sk_buff *skb, struct net_device *dev)
if (skb->len <= 0)
return 0;

if (skb->len < ETH_ZLEN && lp->chip == HP100_CHIPID_SHASTA) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
return 0;
}
if (lp->chip == HP100_CHIPID_SHASTA && skb_padto(skb, ETH_ZLEN))
return 0;

/* Get Tx ring tail pointer */
if (lp->txrtail->next == lp->txrhead) {
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3 changes: 1 addition & 2 deletions drivers/net/lance.c
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Original file line number Diff line number Diff line change
Expand Up @@ -968,8 +968,7 @@ static int lance_start_xmit(struct sk_buff *skb, struct net_device *dev)
/* The old LANCE chips doesn't automatically pad buffers to min. size. */
if (chip_table[lp->chip_version].flags & LANCE_MUST_PAD) {
if (skb->len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
goto out;
lp->tx_ring[entry].length = -ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/lasi_82596.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1083,8 +1083,7 @@ static int i596_start_xmit(struct sk_buff *skb, struct net_device *dev)
skb->len, skb->data));

if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/lp486e.c
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Original file line number Diff line number Diff line change
Expand Up @@ -877,8 +877,7 @@ static int i596_start_xmit (struct sk_buff *skb, struct net_device *dev) {
length = skb->len;

if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/myri10ge/myri10ge.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1939,8 +1939,7 @@ static int myri10ge_xmit(struct sk_buff *skb, struct net_device *dev)

/* pad frames to at least ETH_ZLEN bytes */
if (unlikely(skb->len < ETH_ZLEN)) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL) {
if (skb_padto(skb, ETH_ZLEN)) {
/* The packet is gone, so we must
* return 0 */
mgp->stats.tx_dropped += 1;
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3 changes: 1 addition & 2 deletions drivers/net/pcmcia/fmvj18x_cs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -831,8 +831,7 @@ static int fjn_start_xmit(struct sk_buff *skb, struct net_device *dev)

if (length < ETH_ZLEN)
{
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/pcmcia/xirc2ps_cs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1374,8 +1374,7 @@ do_start_xmit(struct sk_buff *skb, struct net_device *dev)
*/
if (pktlen < ETH_ZLEN)
{
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
pktlen = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/r8169.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2222,8 +2222,7 @@ static int rtl8169_start_xmit(struct sk_buff *skb, struct net_device *dev)
len = skb->len;

if (unlikely(len < ETH_ZLEN)) {
skb = skb_padto(skb, ETH_ZLEN);
if (!skb)
if (skb_padto(skb, ETH_ZLEN))
goto err_update_stats;
len = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/seeq8005.c
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Original file line number Diff line number Diff line change
Expand Up @@ -396,8 +396,7 @@ static int seeq8005_send_packet(struct sk_buff *skb, struct net_device *dev)
unsigned char *buf;

if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/sis190.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1156,8 +1156,7 @@ static int sis190_start_xmit(struct sk_buff *skb, struct net_device *dev)
dma_addr_t mapping;

if (unlikely(skb->len < ETH_ZLEN)) {
skb = skb_padto(skb, ETH_ZLEN);
if (!skb) {
if (skb_padto(skb, ETH_ZLEN)) {
tp->stats.tx_dropped++;
goto out;
}
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2 changes: 1 addition & 1 deletion drivers/net/sk98lin/skge.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1525,7 +1525,7 @@ struct sk_buff *pMessage) /* pointer to send-message */
** This is to resolve faulty padding by the HW with 0xaa bytes.
*/
if (BytesSend < C_LEN_ETHERNET_MINSIZE) {
if ((pMessage = skb_padto(pMessage, C_LEN_ETHERNET_MINSIZE)) == NULL) {
if (skb_padto(pMessage, C_LEN_ETHERNET_MINSIZE)) {
spin_unlock_irqrestore(&pTxPort->TxDesRingLock, Flags);
return 0;
}
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3 changes: 1 addition & 2 deletions drivers/net/skge.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2310,8 +2310,7 @@ static int skge_xmit_frame(struct sk_buff *skb, struct net_device *dev)
u64 map;
unsigned long flags;

skb = skb_padto(skb, ETH_ZLEN);
if (!skb)
if (skb_padto(skb, ETH_ZLEN))
return NETDEV_TX_OK;

if (!spin_trylock_irqsave(&skge->tx_lock, flags))
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3 changes: 1 addition & 2 deletions drivers/net/smc9194.c
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Original file line number Diff line number Diff line change
Expand Up @@ -523,8 +523,7 @@ static int smc_wait_to_send_packet( struct sk_buff * skb, struct net_device * de
length = skb->len;

if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL) {
if (skb_padto(skb, ETH_ZLEN)) {
netif_wake_queue(dev);
return 0;
}
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3 changes: 1 addition & 2 deletions drivers/net/sonic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -231,8 +231,7 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev)

length = skb->len;
if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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3 changes: 1 addition & 2 deletions drivers/net/starfire.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1349,8 +1349,7 @@ static int start_tx(struct sk_buff *skb, struct net_device *dev)

#if defined(ZEROCOPY) && defined(HAS_BROKEN_FIRMWARE)
if (skb->ip_summed == CHECKSUM_HW) {
skb = skb_padto(skb, (skb->len + PADDING_MASK) & ~PADDING_MASK);
if (skb == NULL)
if (skb_padto(skb, (skb->len + PADDING_MASK) & ~PADDING_MASK))
return NETDEV_TX_OK;
}
#endif /* ZEROCOPY && HAS_BROKEN_FIRMWARE */
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7 changes: 2 additions & 5 deletions drivers/net/via-rhine.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1284,11 +1284,8 @@ static int rhine_start_tx(struct sk_buff *skb, struct net_device *dev)
/* Calculate the next Tx descriptor entry. */
entry = rp->cur_tx % TX_RING_SIZE;

if (skb->len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
return 0;
}
if (skb_padto(skb, ETH_ZLEN))
return 0;

rp->tx_skbuff[entry] = skb;

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3 changes: 1 addition & 2 deletions drivers/net/wireless/ray_cs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -924,8 +924,7 @@ static int ray_dev_start_xmit(struct sk_buff *skb, struct net_device *dev)

if (length < ETH_ZLEN)
{
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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7 changes: 2 additions & 5 deletions drivers/net/wireless/wavelan_cs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3194,11 +3194,8 @@ wavelan_packet_xmit(struct sk_buff * skb,
* and we don't have the Ethernet specific requirement of beeing
* able to detect collisions, therefore in theory we don't really
* need to pad. Jean II */
if (skb->len < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
return 0;
}
if (skb_padto(skb, ETH_ZLEN))
return 0;

wv_packet_write(dev, skb->data, skb->len);

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12 changes: 5 additions & 7 deletions drivers/net/yellowfin.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -862,13 +862,11 @@ static int yellowfin_start_xmit(struct sk_buff *skb, struct net_device *dev)
/* Fix GX chipset errata. */
if (cacheline_end > 24 || cacheline_end == 0) {
len = skb->len + 32 - cacheline_end + 1;
if (len != skb->len)
skb = skb_padto(skb, len);
}
if (skb == NULL) {
yp->tx_skbuff[entry] = NULL;
netif_wake_queue(dev);
return 0;
if (skb_padto(skb, len)) {
yp->tx_skbuff[entry] = NULL;
netif_wake_queue(dev);
return 0;
}
}
}
yp->tx_skbuff[entry] = skb;
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3 changes: 1 addition & 2 deletions drivers/net/znet.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -544,8 +544,7 @@ static int znet_send_packet(struct sk_buff *skb, struct net_device *dev)
printk(KERN_DEBUG "%s: ZNet_send_packet.\n", dev->name);

if (length < ETH_ZLEN) {
skb = skb_padto(skb, ETH_ZLEN);
if (skb == NULL)
if (skb_padto(skb, ETH_ZLEN))
return 0;
length = ETH_ZLEN;
}
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11 changes: 5 additions & 6 deletions include/linux/skbuff.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -345,7 +345,7 @@ extern struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
extern struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
int newheadroom, int newtailroom,
gfp_t priority);
extern struct sk_buff * skb_pad(struct sk_buff *skb, int pad);
extern int skb_pad(struct sk_buff *skb, int pad);
#define dev_kfree_skb(a) kfree_skb(a)
extern void skb_over_panic(struct sk_buff *skb, int len,
void *here);
Expand Down Expand Up @@ -1122,16 +1122,15 @@ static inline int skb_cow(struct sk_buff *skb, unsigned int headroom)
*
* Pads up a buffer to ensure the trailing bytes exist and are
* blanked. If the buffer already contains sufficient data it
* is untouched. Returns the buffer, which may be a replacement
* for the original, or NULL for out of memory - in which case
* the original buffer is still freed.
* is untouched. Otherwise it is extended. Returns zero on
* success. The skb is freed on error.
*/

static inline struct sk_buff *skb_padto(struct sk_buff *skb, unsigned int len)
static inline int skb_padto(struct sk_buff *skb, unsigned int len)
{
unsigned int size = skb->len;
if (likely(size >= len))
return skb;
return 0;
return skb_pad(skb, len-size);
}

Expand Down
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