[NET]: convert network timestamps to ktime_t

We currently use a special structure (struct skb_timeval) and plain
'struct timeval' to store packet timestamps in sk_buffs and struct
sock.

This has some drawbacks :
- Fixed resolution of micro second.
- Waste of space on 64bit platforms where sizeof(struct timeval)=16

I suggest using ktime_t that is a nice abstraction of high resolution
time services, currently capable of nanosecond resolution.

As sizeof(ktime_t) is 8 bytes, using ktime_t in 'struct sock' permits
a 8 byte shrink of this structure on 64bit architectures. Some other
structures also benefit from this size reduction (struct ipq in
ipv4/ip_fragment.c, struct frag_queue in ipv6/reassembly.c, ...)

Once this ktime infrastructure adopted, we can more easily provide
nanosecond resolution on top of it. (ioctl SIOCGSTAMPNS and/or
SO_TIMESTAMPNS/SCM_TIMESTAMPNS)

Note : this patch includes a bug correction in
compat_sock_get_timestamp() where a "err = 0;" was missing (so this
syscall returned -ENOENT instead of 0)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
CC: Stephen Hemminger <shemminger@linux-foundation.org>
CC: John find <linux.kernel@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 28d47e8..f9866a8 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -582,6 +582,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
 	unsigned long status = TP_STATUS_LOSING|TP_STATUS_USER;
 	unsigned short macoff, netoff;
 	struct sk_buff *copy_skb = NULL;
+	struct timeval tv;
 
 	if (skb->pkt_type == PACKET_LOOPBACK)
 		goto drop;
@@ -656,12 +657,13 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
 	h->tp_snaplen = snaplen;
 	h->tp_mac = macoff;
 	h->tp_net = netoff;
-	if (skb->tstamp.off_sec == 0) {
+	if (skb->tstamp.tv64 == 0) {
 		__net_timestamp(skb);
 		sock_enable_timestamp(sk);
 	}
-	h->tp_sec = skb->tstamp.off_sec;
-	h->tp_usec = skb->tstamp.off_usec;
+	tv = ktime_to_timeval(skb->tstamp);
+	h->tp_sec = tv.tv_sec;
+	h->tp_usec = tv.tv_usec;
 
 	sll = (struct sockaddr_ll*)((u8*)h + TPACKET_ALIGN(sizeof(*h)));
 	sll->sll_halen = 0;