packet: move hw/sw timestamp extraction into a small helper

This patch introduces a small, internal helper function, that is used by
PF_PACKET. Based on the flags that are passed, it extracts the packet
timestamp in the receive path. This is merely a refactoring to remove
some duplicate code in tpacket_rcv(), to make it more readable, and to
enable others to use this function in PF_PACKET as well, e.g. for TX.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/packet/af_packet.c

@@ -1657,6 +1657,26 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 	return 0;
 }
 
+static void tpacket_get_timestamp(struct sk_buff *skb, struct timespec *ts,
+				  unsigned int flags)
+{
+	struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
+
+	if (shhwtstamps) {
+		if ((flags & SOF_TIMESTAMPING_SYS_HARDWARE) &&
+		    ktime_to_timespec_cond(shhwtstamps->syststamp, ts))
+			return;
+		if ((flags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
+		    ktime_to_timespec_cond(shhwtstamps->hwtstamp, ts))
+			return;
+	}
+
+	if (ktime_to_timespec_cond(skb->tstamp, ts))
+		return;
+
+	getnstimeofday(ts);
+}
+
 static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		       struct packet_type *pt, struct net_device *orig_dev)
 {
@@ -1670,9 +1690,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	unsigned long status = TP_STATUS_USER;
 	unsigned short macoff, netoff, hdrlen;
 	struct sk_buff *copy_skb = NULL;
-	struct timeval tv;
 	struct timespec ts;
-	struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
 
 	if (skb->pkt_type == PACKET_LOOPBACK)
 		goto drop;
@@ -1755,6 +1773,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 	spin_unlock(&sk->sk_receive_queue.lock);
 
 	skb_copy_bits(skb, 0, h.raw + macoff, snaplen);
+	tpacket_get_timestamp(skb, &ts, po->tp_tstamp);
 
 	switch (po->tp_version) {
 	case TPACKET_V1:
@@ -1762,18 +1781,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		h.h1->tp_snaplen = snaplen;
 		h.h1->tp_mac = macoff;
 		h.h1->tp_net = netoff;
-		if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
-				&& shhwtstamps->syststamp.tv64)
-			tv = ktime_to_timeval(shhwtstamps->syststamp);
-		else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
-				&& shhwtstamps->hwtstamp.tv64)
-			tv = ktime_to_timeval(shhwtstamps->hwtstamp);
-		else if (skb->tstamp.tv64)
-			tv = ktime_to_timeval(skb->tstamp);
-		else
-			do_gettimeofday(&tv);
-		h.h1->tp_sec = tv.tv_sec;
-		h.h1->tp_usec = tv.tv_usec;
+		h.h1->tp_sec = ts.tv_sec;
+		h.h1->tp_usec = ts.tv_nsec / NSEC_PER_USEC;
 		hdrlen = sizeof(*h.h1);
 		break;
 	case TPACKET_V2:
@@ -1781,16 +1790,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		h.h2->tp_snaplen = snaplen;
 		h.h2->tp_mac = macoff;
 		h.h2->tp_net = netoff;
-		if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
-				&& shhwtstamps->syststamp.tv64)
-			ts = ktime_to_timespec(shhwtstamps->syststamp);
-		else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
-				&& shhwtstamps->hwtstamp.tv64)
-			ts = ktime_to_timespec(shhwtstamps->hwtstamp);
-		else if (skb->tstamp.tv64)
-			ts = ktime_to_timespec(skb->tstamp);
-		else
-			getnstimeofday(&ts);
 		h.h2->tp_sec = ts.tv_sec;
 		h.h2->tp_nsec = ts.tv_nsec;
 		if (vlan_tx_tag_present(skb)) {
@@ -1811,16 +1810,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		h.h3->tp_snaplen = snaplen;
 		h.h3->tp_mac = macoff;
 		h.h3->tp_net = netoff;
-		if ((po->tp_tstamp & SOF_TIMESTAMPING_SYS_HARDWARE)
-				&& shhwtstamps->syststamp.tv64)
-			ts = ktime_to_timespec(shhwtstamps->syststamp);
-		else if ((po->tp_tstamp & SOF_TIMESTAMPING_RAW_HARDWARE)
-				&& shhwtstamps->hwtstamp.tv64)
-			ts = ktime_to_timespec(shhwtstamps->hwtstamp);
-		else if (skb->tstamp.tv64)
-			ts = ktime_to_timespec(skb->tstamp);
-		else
-			getnstimeofday(&ts);
 		h.h3->tp_sec  = ts.tv_sec;
 		h.h3->tp_nsec = ts.tv_nsec;
 		hdrlen = sizeof(*h.h3);