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dp83640: Fix receive timestamp race condition
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When timestamping received packets, rx_timestamp_work may be scheduled
before the timestamps is received from the hardware resulting in the
packet beeing delivered without the timestamp.

This is fixed by changing the receive timestamp path:

On receiving a packet that need timestamping, the rxts list is
traversed.  If a match is found, packet+timestamp are delivered,
otherwise the packet is added to a rx_queue.

When a timestamp arrives rx_queue is traversed and if a matching
packet is found, it is delivered with the timestamp. Otherwise the
timestamp is added to the rxts list for matching with packets arriving
later.

In case the hardware drops a timestamp, a workqueue regularly checks
the queue for old packets and delivers them without a timestamp.

Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Stefan Sørensen authored and David S. Miller committed Jul 23, 2014
1 parent 3676326 commit 63502b8
Showing 1 changed file with 102 additions and 71 deletions.
173 changes: 102 additions & 71 deletions drivers/net/phy/dp83640.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,10 @@
#define ENDIAN_FLAG PSF_ENDIAN
#endif

#define SKB_PTP_TYPE(__skb) (*(unsigned int *)((__skb)->cb))
struct dp83640_skb_info {
int ptp_type;
unsigned long tmo;
};

struct phy_rxts {
u16 ns_lo; /* ns[15:0] */
Expand Down Expand Up @@ -768,10 +771,51 @@ static int decode_evnt(struct dp83640_private *dp83640,
return parsed * sizeof(u16);
}

static int match(struct sk_buff *skb, unsigned int type, struct rxts *rxts)
{
u16 *seqid;
unsigned int offset = 0;
u8 *msgtype, *data = skb_mac_header(skb);

/* check sequenceID, messageType, 12 bit hash of offset 20-29 */

if (type & PTP_CLASS_VLAN)
offset += VLAN_HLEN;

switch (type & PTP_CLASS_PMASK) {
case PTP_CLASS_IPV4:
offset += ETH_HLEN + IPV4_HLEN(data) + UDP_HLEN;
break;
case PTP_CLASS_IPV6:
offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
break;
case PTP_CLASS_L2:
offset += ETH_HLEN;
break;
default:
return 0;
}

if (skb->len + ETH_HLEN < offset + OFF_PTP_SEQUENCE_ID + sizeof(*seqid))
return 0;

if (unlikely(type & PTP_CLASS_V1))
msgtype = data + offset + OFF_PTP_CONTROL;
else
msgtype = data + offset;

seqid = (u16 *)(data + offset + OFF_PTP_SEQUENCE_ID);

return rxts->msgtype == (*msgtype & 0xf) &&
rxts->seqid == ntohs(*seqid);
}

static void decode_rxts(struct dp83640_private *dp83640,
struct phy_rxts *phy_rxts)
{
struct rxts *rxts;
struct skb_shared_hwtstamps *shhwtstamps = NULL;
struct sk_buff *skb;
unsigned long flags;

spin_lock_irqsave(&dp83640->rx_lock, flags);
Expand All @@ -785,7 +829,26 @@ static void decode_rxts(struct dp83640_private *dp83640,
rxts = list_first_entry(&dp83640->rxpool, struct rxts, list);
list_del_init(&rxts->list);
phy2rxts(phy_rxts, rxts);
list_add_tail(&rxts->list, &dp83640->rxts);

spin_lock_irqsave(&dp83640->rx_queue.lock, flags);
skb_queue_walk(&dp83640->rx_queue, skb) {
struct dp83640_skb_info *skb_info;

skb_info = (struct dp83640_skb_info *)skb->cb;
if (match(skb, skb_info->ptp_type, rxts)) {
__skb_unlink(skb, &dp83640->rx_queue);
shhwtstamps = skb_hwtstamps(skb);
memset(shhwtstamps, 0, sizeof(*shhwtstamps));
shhwtstamps->hwtstamp = ns_to_ktime(rxts->ns);
netif_rx_ni(skb);
list_add(&rxts->list, &dp83640->rxpool);
break;
}
}
spin_unlock_irqrestore(&dp83640->rx_queue.lock, flags);

if (!shhwtstamps)
list_add_tail(&rxts->list, &dp83640->rxts);
out:
spin_unlock_irqrestore(&dp83640->rx_lock, flags);
}
Expand Down Expand Up @@ -887,45 +950,6 @@ static int is_sync(struct sk_buff *skb, int type)
return (*msgtype & 0xf) == 0;
}

static int match(struct sk_buff *skb, unsigned int type, struct rxts *rxts)
{
u16 *seqid;
unsigned int offset = 0;
u8 *msgtype, *data = skb_mac_header(skb);

/* check sequenceID, messageType, 12 bit hash of offset 20-29 */

if (type & PTP_CLASS_VLAN)
offset += VLAN_HLEN;

switch (type & PTP_CLASS_PMASK) {
case PTP_CLASS_IPV4:
offset += ETH_HLEN + IPV4_HLEN(data) + UDP_HLEN;
break;
case PTP_CLASS_IPV6:
offset += ETH_HLEN + IP6_HLEN + UDP_HLEN;
break;
case PTP_CLASS_L2:
offset += ETH_HLEN;
break;
default:
return 0;
}

if (skb->len + ETH_HLEN < offset + OFF_PTP_SEQUENCE_ID + sizeof(*seqid))
return 0;

if (unlikely(type & PTP_CLASS_V1))
msgtype = data + offset + OFF_PTP_CONTROL;
else
msgtype = data + offset;

seqid = (u16 *)(data + offset + OFF_PTP_SEQUENCE_ID);

return rxts->msgtype == (*msgtype & 0xf) &&
rxts->seqid == ntohs(*seqid);
}

static void dp83640_free_clocks(void)
{
struct dp83640_clock *clock;
Expand Down Expand Up @@ -1302,44 +1326,34 @@ static void rx_timestamp_work(struct work_struct *work)
{
struct dp83640_private *dp83640 =
container_of(work, struct dp83640_private, ts_work);
struct list_head *this, *next;
struct rxts *rxts;
struct skb_shared_hwtstamps *shhwtstamps;
struct sk_buff *skb;
unsigned int type;
unsigned long flags;

/* Deliver each deferred packet, with or without a time stamp. */

while ((skb = skb_dequeue(&dp83640->rx_queue)) != NULL) {
type = SKB_PTP_TYPE(skb);
spin_lock_irqsave(&dp83640->rx_lock, flags);
list_for_each_safe(this, next, &dp83640->rxts) {
rxts = list_entry(this, struct rxts, list);
if (match(skb, type, rxts)) {
shhwtstamps = skb_hwtstamps(skb);
memset(shhwtstamps, 0, sizeof(*shhwtstamps));
shhwtstamps->hwtstamp = ns_to_ktime(rxts->ns);
list_del_init(&rxts->list);
list_add(&rxts->list, &dp83640->rxpool);
break;
}
/* Deliver expired packets. */
while ((skb = skb_dequeue(&dp83640->rx_queue))) {
struct dp83640_skb_info *skb_info;

skb_info = (struct dp83640_skb_info *)skb->cb;
if (!time_after(jiffies, skb_info->tmo)) {
skb_queue_head(&dp83640->rx_queue, skb);
break;
}
spin_unlock_irqrestore(&dp83640->rx_lock, flags);

netif_rx_ni(skb);
}

/* Clear out expired time stamps. */

spin_lock_irqsave(&dp83640->rx_lock, flags);
prune_rx_ts(dp83640);
spin_unlock_irqrestore(&dp83640->rx_lock, flags);
if (!skb_queue_empty(&dp83640->rx_queue))
schedule_work(&dp83640->ts_work);
}

static bool dp83640_rxtstamp(struct phy_device *phydev,
struct sk_buff *skb, int type)
{
struct dp83640_private *dp83640 = phydev->priv;
struct dp83640_skb_info *skb_info = (struct dp83640_skb_info *)skb->cb;
struct list_head *this, *next;
struct rxts *rxts;
struct skb_shared_hwtstamps *shhwtstamps = NULL;
unsigned long flags;

if (is_status_frame(skb, type)) {
decode_status_frame(dp83640, skb);
Expand All @@ -1350,9 +1364,27 @@ static bool dp83640_rxtstamp(struct phy_device *phydev,
if (!dp83640->hwts_rx_en)
return false;

SKB_PTP_TYPE(skb) = type;
skb_queue_tail(&dp83640->rx_queue, skb);
schedule_work(&dp83640->ts_work);
spin_lock_irqsave(&dp83640->rx_lock, flags);
list_for_each_safe(this, next, &dp83640->rxts) {
rxts = list_entry(this, struct rxts, list);
if (match(skb, type, rxts)) {
shhwtstamps = skb_hwtstamps(skb);
memset(shhwtstamps, 0, sizeof(*shhwtstamps));
shhwtstamps->hwtstamp = ns_to_ktime(rxts->ns);
netif_rx_ni(skb);
list_del_init(&rxts->list);
list_add(&rxts->list, &dp83640->rxpool);
break;
}
}
spin_unlock_irqrestore(&dp83640->rx_lock, flags);

if (!shhwtstamps) {
skb_info->ptp_type = type;
skb_info->tmo = jiffies + 2;
skb_queue_tail(&dp83640->rx_queue, skb);
schedule_work(&dp83640->ts_work);
}

return true;
}
Expand All @@ -1373,7 +1405,6 @@ static void dp83640_txtstamp(struct phy_device *phydev,
case HWTSTAMP_TX_ON:
skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
skb_queue_tail(&dp83640->tx_queue, skb);
schedule_work(&dp83640->ts_work);
break;

case HWTSTAMP_TX_OFF:
Expand Down

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