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Commit 614f60fa authored by Scott McMillan's avatar Scott McMillan Committed by David S. Miller
Browse files

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: default avatarScott McMillan <scott.a.mcmillan@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7dad171c

Documentation/networking/packet_mmap.txt

+26 −0
Original line number Diff line number Diff line
@@ -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

--------------------------------------------------------------------------------

include/linux/if_packet.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

net/packet/af_packet.c

+35 −2
Original line number Diff line number Diff line
@@ -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;

	}