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caif: Stash away hijacked skb destructor and call it later

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This patch adds functionality for avoiding orphaning SKB too early.
The original skb is stashed away and the original destructor is called
from the hi-jacked flow-on callback. If CAIF interface goes down and a
hi-jacked SKB exists, the original skb->destructor is restored.

Signed-off-by: Sjur Brændeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
sjur.brandeland@stericsson.com 2011-12-04 11:22:55 +00:00 committed by David S. Miller
parent 0e4c7d85d5
commit 7d31130428
1 changed files with 33 additions and 1 deletions
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34
net/caif/caif_dev.c
View File

@ -36,6 +36,8 @@ struct caif_device_entry {
struct net_device *netdev;
int __percpu *pcpu_refcnt;
spinlock_t flow_lock;
struct sk_buff *xoff_skb;
void (*xoff_skb_dtor)(struct sk_buff *skb);
bool xoff;
};
@ -133,6 +135,7 @@ static struct caif_device_entry *caif_get(struct net_device *dev)
void caif_flow_cb(struct sk_buff *skb)
{
struct caif_device_entry *caifd;
void (*dtor)(struct sk_buff *skb) = NULL;
bool send_xoff;
WARN_ON(skb->dev == NULL);
@ -145,8 +148,17 @@ void caif_flow_cb(struct sk_buff *skb)
spin_lock_bh(&caifd->flow_lock);
send_xoff = caifd->xoff;
caifd->xoff = 0;
if (!WARN_ON(caifd->xoff_skb_dtor == NULL)) {
WARN_ON(caifd->xoff_skb != skb);
dtor = caifd->xoff_skb_dtor;
caifd->xoff_skb = NULL;
caifd->xoff_skb_dtor = NULL;
}
spin_unlock_bh(&caifd->flow_lock);
if (dtor)
dtor(skb);
if (send_xoff)
caifd->layer.up->
ctrlcmd(caifd->layer.up,
@ -210,8 +222,10 @@ static int transmit(struct cflayer *layer, struct cfpkt *pkt)
netif_queue_stopped(caifd->netdev),
qlen, high);
caifd->xoff = 1;
caifd->xoff_skb = skb;
caifd->xoff_skb_dtor = skb->destructor;
skb->destructor = caif_flow_cb;
spin_unlock_bh(&caifd->flow_lock);
skb_orphan(skb);
caifd->layer.up->ctrlcmd(caifd->layer.up,
_CAIF_CTRLCMD_PHYIF_FLOW_OFF_IND,
@ -420,6 +434,24 @@ static int caif_device_notify(struct notifier_block *me, unsigned long what,
caifd->layer.up->ctrlcmd(caifd->layer.up,
_CAIF_CTRLCMD_PHYIF_DOWN_IND,
caifd->layer.id);
spin_lock_bh(&caifd->flow_lock);
/*
* Replace our xoff-destructor with original destructor.
* We trust that skb->destructor *always* is called before
* the skb reference is invalid. The hijacked SKB destructor
* takes the flow_lock so manipulating the skb->destructor here
* should be safe.
*/
if (caifd->xoff_skb_dtor != NULL && caifd->xoff_skb != NULL)
caifd->xoff_skb->destructor = caifd->xoff_skb_dtor;
caifd->xoff = 0;
caifd->xoff_skb_dtor = NULL;
caifd->xoff_skb = NULL;
spin_unlock_bh(&caifd->flow_lock);
caifd_put(caifd);
break;