packet_mmap: expose hw packet timestamps to network packet capture utilities

This patch adds a setting, PACKET_TIMESTAMP, to specify the packet
timestamp source that is exported to capture utilities like tcpdump by
packet_mmap.

PACKET_TIMESTAMP accepts the same integer bit field as
SO_TIMESTAMPING.  However, only the SOF_TIMESTAMPING_SYS_HARDWARE and
SOF_TIMESTAMPING_RAW_HARDWARE values are currently recognized by
PACKET_TIMESTAMP.  SOF_TIMESTAMPING_SYS_HARDWARE takes precedence over
SOF_TIMESTAMPING_RAW_HARDWARE if both bits are set.

If PACKET_TIMESTAMP is not set, a software timestamp generated inside
the networking stack is used (the behavior before this setting was
added).

Signed-off-by: Scott McMillan <scott.a.mcmillan@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 62 insertions, 2 deletions

diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt
index 98f71a5cef0..2546aa4dc23 100644
--- a/Documentation/networking/packet_mmap.txt
+++ b/Documentation/networking/packet_mmap.txt
@@ -493,6 +493,32 @@ The user can also use poll() to check if a buffer is available:
     pfd.events = POLLOUT;
     retval = poll(&pfd, 1, timeout);
 
+-------------------------------------------------------------------------------
++ PACKET_TIMESTAMP
+-------------------------------------------------------------------------------
+
+The PACKET_TIMESTAMP setting determines the source of the timestamp in
+the packet meta information.  If your NIC is capable of timestamping
+packets in hardware, you can request those hardware timestamps to used.
+Note: you may need to enable the generation of hardware timestamps with
+SIOCSHWTSTAMP.
+
+PACKET_TIMESTAMP accepts the same integer bit field as
+SO_TIMESTAMPING.  However, only the SOF_TIMESTAMPING_SYS_HARDWARE
+and SOF_TIMESTAMPING_RAW_HARDWARE values are recognized by
+PACKET_TIMESTAMP.  SOF_TIMESTAMPING_SYS_HARDWARE takes precedence over
+SOF_TIMESTAMPING_RAW_HARDWARE if both bits are set.
+
+    int req = 0;
+    req |= SOF_TIMESTAMPING_SYS_HARDWARE;
+    setsockopt(fd, SOL_PACKET, PACKET_TIMESTAMP, (void *) &req, sizeof(req))
+
+If PACKET_TIMESTAMP is not set, a software timestamp generated inside
+the networking stack is used (the behavior before this setting was added).
+
+See include/linux/net_tstamp.h and Documentation/networking/timestamping
+for more information on hardware timestamps.
+
 --------------------------------------------------------------------------------
 + THANKS
 --------------------------------------------------------------------------------
diff --git a/include/linux/if_packet.h b/include/linux/if_packet.h
index 6ac23ef1801..72bfa5a034d 100644
--- a/include/linux/if_packet.h
+++ b/include/linux/if_packet.h
@@ -48,6 +48,7 @@ struct sockaddr_ll {
 #define PACKET_LOSS                     14
 #define PACKET_VNET_HDR                 15
 #define PACKET_TX_TIMESTAMP             16
+#define PACKET_TIMESTAMP                17
 
 struct tpacket_stats {
         unsigned int    tp_packets;
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 2078a277e06..9a17f28b125 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -83,6 +83,7 @@
 #include <linux/if_vlan.h>
 #include <linux/virtio_net.h>
 #include <linux/errqueue.h>
+#include <linux/net_tstamp.h>
 
 #ifdef CONFIG_INET
 #include <net/inet_common.h>
@@ -202,6 +203,7 @@ struct packet_sock {
         unsigned int            tp_hdrlen;
         unsigned int            tp_reserve;
         unsigned int            tp_loss:1;
+        unsigned int            tp_tstamp;
         struct packet_type      prot_hook ____cacheline_aligned_in_smp;
 };
 
@@ -656,6 +658,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
         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;
@@ -737,7 +740,13 @@ 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 (skb->tstamp.tv64)
+                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);
@@ -750,7 +759,13 @@ 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 (skb->tstamp.tv64)
+                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);
@@ -2027,6 +2042,18 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
                 po->has_vnet_hdr = !!val;
                 return 0;
         }
+        case PACKET_TIMESTAMP:
+        {
+                int val;
+
+                if (optlen != sizeof(val))
+                        return -EINVAL;
+                if (copy_from_user(&val, optval, sizeof(val)))
+                        return -EFAULT;
+
+                po->tp_tstamp = val;
+                return 0;
+        }
         default:
                 return -ENOPROTOOPT;
         }
@@ -2119,6 +2146,12 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
                 val = po->tp_loss;
                 data = &val;
                 break;
+        case PACKET_TIMESTAMP:
+                if (len > sizeof(int))
+                        len = sizeof(int);
+                val = po->tp_tstamp;
+                data = &val;
+                break;
         default:
                 return -ENOPROTOOPT;
         }