net-timestamp: SCHED timestamp on entering packet scheduler

Kernel transmit latency is often incurred in the packet scheduler.
Introduce a new timestamp on transmission just before entering the
scheduler. When data travels through multiple devices (bonding,
tunneling, ...) each device will export an individual timestamp.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 12 insertions, 3 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 0e35b3af7317..50e1e9b3a5a5 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -229,7 +229,7 @@ enum {
         /* generate hardware time stamp */
         SKBTX_HW_TSTAMP = 1 << 0,
 
-        /* generate software time stamp */
+        /* generate software time stamp when queueing packet to NIC */
         SKBTX_SW_TSTAMP = 1 << 1,
 
         /* device driver is going to provide hardware time stamp */
@@ -247,9 +247,12 @@ enum {
          * all frags to avoid possible bad checksum
          */
         SKBTX_SHARED_FRAG = 1 << 5,
+
+        /* generate software time stamp when entering packet scheduling */
+        SKBTX_SCHED_TSTAMP = 1 << 6,
 };
 
-#define SKBTX_ANY_SW_TSTAMP     SKBTX_SW_TSTAMP
+#define SKBTX_ANY_SW_TSTAMP     (SKBTX_SW_TSTAMP | SKBTX_SCHED_TSTAMP)
 #define SKBTX_ANY_TSTAMP        (SKBTX_HW_TSTAMP | SKBTX_ANY_SW_TSTAMP)
 
 /*
@@ -2695,6 +2698,10 @@ static inline bool skb_defer_rx_timestamp(struct sk_buff *skb)
 void skb_complete_tx_timestamp(struct sk_buff *skb,
                                struct skb_shared_hwtstamps *hwtstamps);
 
+void __skb_tstamp_tx(struct sk_buff *orig_skb,
+                     struct skb_shared_hwtstamps *hwtstamps,
+                     struct sock *sk, int tstype);
+
 /**
  * skb_tstamp_tx - queue clone of skb with send time stamps
  * @orig_skb:   the original outgoing packet
diff --git a/include/uapi/linux/errqueue.h b/include/uapi/linux/errqueue.h
index accee72cae7c..17437cf297b7 100644
--- a/include/uapi/linux/errqueue.h
+++ b/include/uapi/linux/errqueue.h
@@ -39,6 +39,7 @@ struct scm_timestamping {
  */
 enum {
         SCM_TSTAMP_SND,         /* driver passed skb to NIC, or HW */
+        SCM_TSTAMP_SCHED,       /* data entered the packet scheduler */
 };
 
 #endif /* _UAPI_LINUX_ERRQUEUE_H */
diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
index 1e861d2e1a31..60733845fcdd 100644
--- a/include/uapi/linux/net_tstamp.h
+++ b/include/uapi/linux/net_tstamp.h
@@ -21,8 +21,9 @@ enum {
         SOF_TIMESTAMPING_SYS_HARDWARE = (1<<5),
         SOF_TIMESTAMPING_RAW_HARDWARE = (1<<6),
         SOF_TIMESTAMPING_OPT_ID = (1<<7),
+        SOF_TIMESTAMPING_TX_SCHED = (1<<8),
 
-        SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_ID,
+        SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_TX_SCHED,
         SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
                                  SOF_TIMESTAMPING_LAST
 };