[PATCH net v1 1/3] net: introduce helper to resolve hardware timestamps from skb

[Kohei Enju <kohei@enjuk.jp>]

Move the logic that resolves a hardware timestamp from an skb, including
late timestamp resolution via netdev_get_tstamp(), from net/socket.c to
a common helper.

Let's allow other networking code to reuse the same resolution path.

Signed-off-by: Kohei Enju <kohei@enjuk.jp>
---
 include/linux/skbuff.h | 11 +++++++++++
 net/core/skbuff.c      | 27 +++++++++++++++++++++++++++
 net/socket.c           | 27 +++------------------------
 3 files changed, 41 insertions(+), 24 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2bcf78a4de7b..651a5ae8b11c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -4731,6 +4731,17 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb, const struct sk_buff *ack_skb,
 void skb_tstamp_tx(struct sk_buff *orig_skb,
 		   struct skb_shared_hwtstamps *hwtstamps);
 
+/**
+ * skb_get_hwtstamp - resolve a hardware timestamp from an skb
+ * @skb:	skb carrying the timestamp
+ * @cycles:	true to request the free-running cycle-based timestamp
+ * @if_index:	optional return pointer for the originating netdev ifindex
+ *
+ * Return: resolved hardware timestamp, or the stored skb hwtstamp when no
+ * device-specific late timestamp resolution is needed.
+ */
+ktime_t skb_get_hwtstamp(struct sk_buff *skb, bool cycles, int *if_index);
+
 /**
  * skb_tx_timestamp() - Driver hook for transmit timestamping
  *
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7dad68e3b518..d11f4e2e9391 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5729,6 +5729,33 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
 }
 EXPORT_SYMBOL_GPL(skb_tstamp_tx);
 
+ktime_t skb_get_hwtstamp(struct sk_buff *skb, bool cycles, int *if_index)
+{
+	struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
+	struct net_device *orig_dev;
+	ktime_t hwtstamp;
+
+	if (if_index)
+		*if_index = 0;
+
+	if (!(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_NETDEV))
+		return shhwtstamps->hwtstamp;
+
+	rcu_read_lock();
+	orig_dev = dev_get_by_napi_id(skb_napi_id(skb));
+	if (orig_dev) {
+		if (if_index)
+			*if_index = orig_dev->ifindex;
+		hwtstamp = netdev_get_tstamp(orig_dev, shhwtstamps, cycles);
+	} else {
+		hwtstamp = shhwtstamps->hwtstamp;
+	}
+	rcu_read_unlock();
+
+	return hwtstamp;
+}
+EXPORT_SYMBOL_GPL(skb_get_hwtstamp);
+
 #ifdef CONFIG_WIRELESS
 void skb_complete_wifi_ack(struct sk_buff *skb, bool acked)
 {
diff --git a/net/socket.c b/net/socket.c
index 22a412fdec07..95b21b16a0fc 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -876,21 +876,7 @@ static bool skb_is_swtx_tstamp(const struct sk_buff *skb, int false_tstamp)
 static ktime_t get_timestamp(struct sock *sk, struct sk_buff *skb, int *if_index)
 {
 	bool cycles = READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_BIND_PHC;
-	struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
-	struct net_device *orig_dev;
-	ktime_t hwtstamp;
-
-	rcu_read_lock();
-	orig_dev = dev_get_by_napi_id(skb_napi_id(skb));
-	if (orig_dev) {
-		*if_index = orig_dev->ifindex;
-		hwtstamp = netdev_get_tstamp(orig_dev, shhwtstamps, cycles);
-	} else {
-		hwtstamp = shhwtstamps->hwtstamp;
-	}
-	rcu_read_unlock();
-
-	return hwtstamp;
+	return skb_get_hwtstamp(skb, cycles, if_index);
 }
 
 static void put_ts_pktinfo(struct msghdr *msg, struct sk_buff *skb,
@@ -940,7 +926,6 @@ int skb_get_tx_timestamp(struct sk_buff *skb, struct sock *sk,
 {
 	u32 tsflags = READ_ONCE(sk->sk_tsflags);
 	ktime_t hwtstamp;
-	int if_index = 0;
 
 	if ((tsflags & SOF_TIMESTAMPING_SOFTWARE) &&
 	    ktime_to_timespec64_cond(skb->tstamp, ts))
@@ -950,10 +935,7 @@ int skb_get_tx_timestamp(struct sk_buff *skb, struct sock *sk,
 	    skb_is_swtx_tstamp(skb, false))
 		return -ENOENT;
 
-	if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_NETDEV)
-		hwtstamp = get_timestamp(sk, skb, &if_index);
-	else
-		hwtstamp = skb_hwtstamps(skb)->hwtstamp;
+	hwtstamp = get_timestamp(sk, skb, NULL);
 
 	if (tsflags & SOF_TIMESTAMPING_BIND_PHC)
 		hwtstamp = ptp_convert_timestamp(&hwtstamp,
@@ -1033,10 +1015,7 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 	      !(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER))) &&
 	    !skb_is_swtx_tstamp(skb, false_tstamp)) {
 		if_index = 0;
-		if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_NETDEV)
-			hwtstamp = get_timestamp(sk, skb, &if_index);
-		else
-			hwtstamp = shhwtstamps->hwtstamp;
+		hwtstamp = get_timestamp(sk, skb, &if_index);
 
 		if (tsflags & SOF_TIMESTAMPING_BIND_PHC)
 			hwtstamp = ptp_convert_timestamp(&hwtstamp,
-- 
2.53.0