packet: tx timestamping on tpacket ring

When transmit timestamping is enabled at the socket level, record a
timestamp on packets written to a PACKET_TX_RING. Tx timestamps are
always looped to the application over the socket error queue. Software
timestamps are also written back into the packet frame header in the
packet ring.

Reported-by: Paul Chavent <paul.chavent@onera.fr>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 33 insertions, 0 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 7e387ff64465..ec8ea27733ac 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -339,6 +339,37 @@ static int __packet_get_status(struct packet_sock *po, void *frame)
         }
 }
 
+static void __packet_set_timestamp(struct packet_sock *po, void *frame,
+                                   ktime_t tstamp)
+{
+        union tpacket_uhdr h;
+        struct timespec ts;
+
+        if (!ktime_to_timespec_cond(tstamp, &ts) ||
+            !sock_flag(&po->sk, SOCK_TIMESTAMPING_SOFTWARE))
+                return;
+
+        h.raw = frame;
+        switch (po->tp_version) {
+        case TPACKET_V1:
+                h.h1->tp_sec = ts.tv_sec;
+                h.h1->tp_usec = ts.tv_nsec / NSEC_PER_USEC;
+                break;
+        case TPACKET_V2:
+                h.h2->tp_sec = ts.tv_sec;
+                h.h2->tp_nsec = ts.tv_nsec;
+                break;
+        case TPACKET_V3:
+        default:
+                WARN(1, "TPACKET version not supported.\n");
+                BUG();
+        }
+
+        /* one flush is safe, as both fields always lie on the same cacheline */
+        flush_dcache_page(pgv_to_page(&h.h1->tp_sec));
+        smp_wmb();
+}
+
 static void *packet_lookup_frame(struct packet_sock *po,
                 struct packet_ring_buffer *rb,
                 unsigned int position,
@@ -1877,6 +1908,7 @@ static void tpacket_destruct_skb(struct sk_buff *skb)
                 ph = skb_shinfo(skb)->destructor_arg;
                 BUG_ON(atomic_read(&po->tx_ring.pending) == 0);
                 atomic_dec(&po->tx_ring.pending);
+                __packet_set_timestamp(po, ph, skb->tstamp);
                 __packet_set_status(po, ph, TP_STATUS_AVAILABLE);
         }
 
@@ -1900,6 +1932,7 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
         skb->dev = dev;
         skb->priority = po->sk.sk_priority;
         skb->mark = po->sk.sk_mark;
+        sock_tx_timestamp(&po->sk, &skb_shinfo(skb)->tx_flags);
         skb_shinfo(skb)->destructor_arg = ph.raw;
 
         switch (po->tp_version) {