net: infrastructure for hardware time stamping
The additional per-packet information (16 bytes for time stamps, 1 byte for flags) is stored for all packets in the skb_shared_info struct. This implementation detail is hidden from users of that information via skb_* accessor functions. A separate struct resp. union is used for the additional information so that it can be stored/copied easily outside of skb_shared_info. Compared to previous implementations (reusing the tstamp field depending on the context, optional additional structures) this is the simplest solution. It does not extend sk_buff itself. TX time stamping is implemented in software if the device driver doesn't support hardware time stamping. The new semantic for hardware/software time stamping around ndo_start_xmit() is based on two assumptions about existing network device drivers which don't support hardware time stamping and know nothing about it: - they leave the new skb_shared_tx unmodified - the keep the connection to the originating socket in skb->sk alive, i.e., don't call skb_orphan() Given that skb_shared_tx is new, the first assumption is safe. The second is only true for some drivers. As a result, software TX time stamping currently works with the bnx2 driver, but not with the unmodified igb driver (the two drivers this patch series was tested with). Signed-off-by: Patrick Ohly <patrick.ohly@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick Ohly
David S. Miller
Родитель
cb9eff0978
Коммит
ac45f602ee
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@ -132,6 +132,57 @@ struct skb_frag_struct {
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__u32 size;
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};
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#define HAVE_HW_TIME_STAMP
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/**
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* skb_shared_hwtstamps - hardware time stamps
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*
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* @hwtstamp: hardware time stamp transformed into duration
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* since arbitrary point in time
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* @syststamp: hwtstamp transformed to system time base
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*
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* Software time stamps generated by ktime_get_real() are stored in
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* skb->tstamp. The relation between the different kinds of time
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* stamps is as follows:
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*
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* syststamp and tstamp can be compared against each other in
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* arbitrary combinations. The accuracy of a
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* syststamp/tstamp/"syststamp from other device" comparison is
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* limited by the accuracy of the transformation into system time
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* base. This depends on the device driver and its underlying
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* hardware.
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*
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* hwtstamps can only be compared against other hwtstamps from
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* the same device.
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*
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* This structure is attached to packets as part of the
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* &skb_shared_info. Use skb_hwtstamps() to get a pointer.
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*/
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struct skb_shared_hwtstamps {
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ktime_t hwtstamp;
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ktime_t syststamp;
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};
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/**
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* skb_shared_tx - instructions for time stamping of outgoing packets
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*
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* @hardware: generate hardware time stamp
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* @software: generate software time stamp
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* @in_progress: device driver is going to provide
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* hardware time stamp
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*
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* These flags are attached to packets as part of the
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* &skb_shared_info. Use skb_tx() to get a pointer.
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*/
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union skb_shared_tx {
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struct {
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__u8 hardware:1,
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software:1,
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in_progress:1;
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};
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__u8 flags;
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};
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/* This data is invariant across clones and lives at
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* the end of the header data, ie. at skb->end.
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*/
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@ -143,10 +194,12 @@ struct skb_shared_info {
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unsigned short gso_segs;
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unsigned short gso_type;
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__be32 ip6_frag_id;
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union skb_shared_tx tx_flags;
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#ifdef CONFIG_HAS_DMA
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unsigned int num_dma_maps;
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#endif
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struct sk_buff *frag_list;
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struct skb_shared_hwtstamps hwtstamps;
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skb_frag_t frags[MAX_SKB_FRAGS];
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#ifdef CONFIG_HAS_DMA
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dma_addr_t dma_maps[MAX_SKB_FRAGS + 1];
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@ -465,6 +518,16 @@ static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
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/* Internal */
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#define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB)))
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static inline struct skb_shared_hwtstamps *skb_hwtstamps(struct sk_buff *skb)
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{
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return &skb_shinfo(skb)->hwtstamps;
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}
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static inline union skb_shared_tx *skb_tx(struct sk_buff *skb)
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{
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return &skb_shinfo(skb)->tx_flags;
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}
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/**
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* skb_queue_empty - check if a queue is empty
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* @list: queue head
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@ -1730,6 +1793,11 @@ static inline void skb_copy_to_linear_data_offset(struct sk_buff *skb,
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extern void skb_init(void);
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static inline ktime_t skb_get_ktime(const struct sk_buff *skb)
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{
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return skb->tstamp;
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}
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/**
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* skb_get_timestamp - get timestamp from a skb
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* @skb: skb to get stamp from
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@ -1739,11 +1807,18 @@ extern void skb_init(void);
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* This function converts the offset back to a struct timeval and stores
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* it in stamp.
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*/
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static inline void skb_get_timestamp(const struct sk_buff *skb, struct timeval *stamp)
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static inline void skb_get_timestamp(const struct sk_buff *skb,
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struct timeval *stamp)
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{
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*stamp = ktime_to_timeval(skb->tstamp);
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}
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static inline void skb_get_timestampns(const struct sk_buff *skb,
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struct timespec *stamp)
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{
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*stamp = ktime_to_timespec(skb->tstamp);
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}
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static inline void __net_timestamp(struct sk_buff *skb)
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{
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skb->tstamp = ktime_get_real();
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@ -1759,6 +1834,20 @@ static inline ktime_t net_invalid_timestamp(void)
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return ktime_set(0, 0);
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}
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/**
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* skb_tstamp_tx - queue clone of skb with send time stamps
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* @orig_skb: the original outgoing packet
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* @hwtstamps: hardware time stamps, may be NULL if not available
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*
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* If the skb has a socket associated, then this function clones the
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* skb (thus sharing the actual data and optional structures), stores
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* the optional hardware time stamping information (if non NULL) or
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* generates a software time stamp (otherwise), then queues the clone
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* to the error queue of the socket. Errors are silently ignored.
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*/
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extern void skb_tstamp_tx(struct sk_buff *orig_skb,
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struct skb_shared_hwtstamps *hwtstamps);
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extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
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extern __sum16 __skb_checksum_complete(struct sk_buff *skb);
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@ -1672,10 +1672,21 @@ static int dev_gso_segment(struct sk_buff *skb)
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return 0;
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}
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static void tstamp_tx(struct sk_buff *skb)
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{
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union skb_shared_tx *shtx =
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skb_tx(skb);
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if (unlikely(shtx->software &&
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!shtx->in_progress)) {
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skb_tstamp_tx(skb, NULL);
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}
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}
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int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
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struct netdev_queue *txq)
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{
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const struct net_device_ops *ops = dev->netdev_ops;
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int rc;
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prefetch(&dev->netdev_ops->ndo_start_xmit);
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if (likely(!skb->next)) {
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@ -1689,13 +1700,29 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
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goto gso;
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}
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return ops->ndo_start_xmit(skb, dev);
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rc = ops->ndo_start_xmit(skb, dev);
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/*
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* TODO: if skb_orphan() was called by
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* dev->hard_start_xmit() (for example, the unmodified
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* igb driver does that; bnx2 doesn't), then
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* skb_tx_software_timestamp() will be unable to send
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* back the time stamp.
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*
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* How can this be prevented? Always create another
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* reference to the socket before calling
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* dev->hard_start_xmit()? Prevent that skb_orphan()
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* does anything in dev->hard_start_xmit() by clearing
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* the skb destructor before the call and restoring it
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* afterwards, then doing the skb_orphan() ourselves?
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*/
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if (likely(!rc))
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tstamp_tx(skb);
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return rc;
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}
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gso:
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do {
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struct sk_buff *nskb = skb->next;
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int rc;
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skb->next = nskb->next;
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nskb->next = NULL;
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@ -1705,6 +1732,7 @@ gso:
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skb->next = nskb;
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return rc;
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}
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tstamp_tx(skb);
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if (unlikely(netif_tx_queue_stopped(txq) && skb->next))
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return NETDEV_TX_BUSY;
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} while (skb->next);
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@ -55,6 +55,7 @@
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#include <linux/rtnetlink.h>
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#include <linux/init.h>
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#include <linux/scatterlist.h>
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#include <linux/errqueue.h>
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#include <net/protocol.h>
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#include <net/dst.h>
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@ -215,7 +216,9 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
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shinfo->gso_segs = 0;
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shinfo->gso_type = 0;
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shinfo->ip6_frag_id = 0;
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shinfo->tx_flags.flags = 0;
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shinfo->frag_list = NULL;
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memset(&shinfo->hwtstamps, 0, sizeof(shinfo->hwtstamps));
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if (fclone) {
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struct sk_buff *child = skb + 1;
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@ -2945,6 +2948,44 @@ int skb_cow_data(struct sk_buff *skb, int tailbits, struct sk_buff **trailer)
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}
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EXPORT_SYMBOL_GPL(skb_cow_data);
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void skb_tstamp_tx(struct sk_buff *orig_skb,
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struct skb_shared_hwtstamps *hwtstamps)
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{
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struct sock *sk = orig_skb->sk;
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struct sock_exterr_skb *serr;
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struct sk_buff *skb;
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int err;
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if (!sk)
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return;
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skb = skb_clone(orig_skb, GFP_ATOMIC);
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if (!skb)
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return;
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if (hwtstamps) {
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*skb_hwtstamps(skb) =
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*hwtstamps;
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} else {
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/*
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* no hardware time stamps available,
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* so keep the skb_shared_tx and only
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* store software time stamp
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*/
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skb->tstamp = ktime_get_real();
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}
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serr = SKB_EXT_ERR(skb);
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memset(serr, 0, sizeof(*serr));
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serr->ee.ee_errno = ENOMSG;
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serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
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err = sock_queue_err_skb(sk, skb);
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if (err)
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kfree_skb(skb);
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}
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EXPORT_SYMBOL_GPL(skb_tstamp_tx);
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/**
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* skb_partial_csum_set - set up and verify partial csum values for packet
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* @skb: the skb to set
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