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>

2 files changed, 16 insertions, 4 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index b370230fe1d3..1c15b189c52b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -132,6 +132,7 @@
 #include <linux/hashtable.h>
 #include <linux/vmalloc.h>
 #include <linux/if_macvlan.h>
+#include <linux/errqueue.h>
 
 #include "net-sysfs.h"
 
@@ -2876,6 +2877,9 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv)
 
         skb_reset_mac_header(skb);
 
+        if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
+                __skb_tstamp_tx(skb, NULL, skb->sk, SCM_TSTAMP_SCHED);
+
         /* Disable soft irqs for various locks below. Also
          * stops preemption for RCU.
          */
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 0df4f1d14c5a..9705c0732aab 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3490,10 +3490,10 @@ int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb)
 }
 EXPORT_SYMBOL(sock_queue_err_skb);
 
-void skb_tstamp_tx(struct sk_buff *orig_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)
 {
-        struct sock *sk = orig_skb->sk;
         struct sock_exterr_skb *serr;
         struct sk_buff *skb;
         int err;
@@ -3521,7 +3521,7 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
         memset(serr, 0, sizeof(*serr));
         serr->ee.ee_errno = ENOMSG;
         serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
-        serr->ee.ee_info = SCM_TSTAMP_SND;
+        serr->ee.ee_info = tstype;
         if (sk->sk_tsflags & SOF_TIMESTAMPING_OPT_ID)
                 serr->ee.ee_data = skb_shinfo(skb)->tskey;
 
@@ -3530,6 +3530,14 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
         if (err)
                 kfree_skb(skb);
 }
+EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
+
+void skb_tstamp_tx(struct sk_buff *orig_skb,
+                   struct skb_shared_hwtstamps *hwtstamps)
+{
+        return __skb_tstamp_tx(orig_skb, hwtstamps, orig_skb->sk,
+                               SCM_TSTAMP_SND);
+}
 EXPORT_SYMBOL_GPL(skb_tstamp_tx);
 
 void skb_complete_wifi_ack(struct sk_buff *skb, bool acked)