From ac45f602ee3d1b6f326f68bc0c2591ceebf05ba4 Mon Sep 17 00:00:00 2001 From: Patrick Ohly Date: Thu, 12 Feb 2009 05:03:37 +0000 Subject: 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 Signed-off-by: David S. Miller --- include/linux/skbuff.h | 91 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 90 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 92470084458..f96bc91bf0a 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -132,6 +132,57 @@ struct skb_frag_struct { __u32 size; }; +#define HAVE_HW_TIME_STAMP + +/** + * skb_shared_hwtstamps - hardware time stamps + * + * @hwtstamp: hardware time stamp transformed into duration + * since arbitrary point in time + * @syststamp: hwtstamp transformed to system time base + * + * Software time stamps generated by ktime_get_real() are stored in + * skb->tstamp. The relation between the different kinds of time + * stamps is as follows: + * + * syststamp and tstamp can be compared against each other in + * arbitrary combinations. The accuracy of a + * syststamp/tstamp/"syststamp from other device" comparison is + * limited by the accuracy of the transformation into system time + * base. This depends on the device driver and its underlying + * hardware. + * + * hwtstamps can only be compared against other hwtstamps from + * the same device. + * + * This structure is attached to packets as part of the + * &skb_shared_info. Use skb_hwtstamps() to get a pointer. + */ +struct skb_shared_hwtstamps { + ktime_t hwtstamp; + ktime_t syststamp; +}; + +/** + * skb_shared_tx - instructions for time stamping of outgoing packets + * + * @hardware: generate hardware time stamp + * @software: generate software time stamp + * @in_progress: device driver is going to provide + * hardware time stamp + * + * These flags are attached to packets as part of the + * &skb_shared_info. Use skb_tx() to get a pointer. + */ +union skb_shared_tx { + struct { + __u8 hardware:1, + software:1, + in_progress:1; + }; + __u8 flags; +}; + /* This data is invariant across clones and lives at * the end of the header data, ie. at skb->end. */ @@ -143,10 +194,12 @@ struct skb_shared_info { unsigned short gso_segs; unsigned short gso_type; __be32 ip6_frag_id; + union skb_shared_tx tx_flags; #ifdef CONFIG_HAS_DMA unsigned int num_dma_maps; #endif struct sk_buff *frag_list; + struct skb_shared_hwtstamps hwtstamps; skb_frag_t frags[MAX_SKB_FRAGS]; #ifdef CONFIG_HAS_DMA dma_addr_t dma_maps[MAX_SKB_FRAGS + 1]; @@ -465,6 +518,16 @@ static inline unsigned char *skb_end_pointer(const struct sk_buff *skb) /* Internal */ #define skb_shinfo(SKB) ((struct skb_shared_info *)(skb_end_pointer(SKB))) +static inline struct skb_shared_hwtstamps *skb_hwtstamps(struct sk_buff *skb) +{ + return &skb_shinfo(skb)->hwtstamps; +} + +static inline union skb_shared_tx *skb_tx(struct sk_buff *skb) +{ + return &skb_shinfo(skb)->tx_flags; +} + /** * skb_queue_empty - check if a queue is empty * @list: queue head @@ -1730,6 +1793,11 @@ static inline void skb_copy_to_linear_data_offset(struct sk_buff *skb, extern void skb_init(void); +static inline ktime_t skb_get_ktime(const struct sk_buff *skb) +{ + return skb->tstamp; +} + /** * skb_get_timestamp - get timestamp from a skb * @skb: skb to get stamp from @@ -1739,11 +1807,18 @@ extern void skb_init(void); * This function converts the offset back to a struct timeval and stores * it in stamp. */ -static inline void skb_get_timestamp(const struct sk_buff *skb, struct timeval *stamp) +static inline void skb_get_timestamp(const struct sk_buff *skb, + struct timeval *stamp) { *stamp = ktime_to_timeval(skb->tstamp); } +static inline void skb_get_timestampns(const struct sk_buff *skb, + struct timespec *stamp) +{ + *stamp = ktime_to_timespec(skb->tstamp); +} + static inline void __net_timestamp(struct sk_buff *skb) { skb->tstamp = ktime_get_real(); @@ -1759,6 +1834,20 @@ static inline ktime_t net_invalid_timestamp(void) return ktime_set(0, 0); } +/** + * skb_tstamp_tx - queue clone of skb with send time stamps + * @orig_skb: the original outgoing packet + * @hwtstamps: hardware time stamps, may be NULL if not available + * + * If the skb has a socket associated, then this function clones the + * skb (thus sharing the actual data and optional structures), stores + * the optional hardware time stamping information (if non NULL) or + * generates a software time stamp (otherwise), then queues the clone + * to the error queue of the socket. Errors are silently ignored. + */ +extern void skb_tstamp_tx(struct sk_buff *orig_skb, + struct skb_shared_hwtstamps *hwtstamps); + extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len); extern __sum16 __skb_checksum_complete(struct sk_buff *skb); -- cgit v1.2.3