[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>

net/bridge/netfilter/ebt_ulog.c

@@ -130,6 +130,7 @@ static void ebt_ulog_packet(unsigned int hooknr, const struct sk_buff *skb,
 	unsigned int group = uloginfo->nlgroup;
 	ebt_ulog_buff_t *ub = &ulog_buffers[group];
 	spinlock_t *lock = &ub->lock;
+	ktime_t kt;
 
 	if ((uloginfo->cprange == 0) ||
 	    (uloginfo->cprange > skb->len + ETH_HLEN))
@@ -164,9 +165,10 @@ static void ebt_ulog_packet(unsigned int hooknr, const struct sk_buff *skb,
 
 	/* Fill in the ulog data */
 	pm->version = EBT_ULOG_VERSION;
-	do_gettimeofday(&pm->stamp);
+	kt = ktime_get_real();
+	pm->stamp = ktime_to_timeval(kt);
 	if (ub->qlen == 1)
-		skb_set_timestamp(ub->skb, &pm->stamp);
+		ub->skb->tstamp = kt;
 	pm->data_len = copy_len;
 	pm->mark = skb->mark;
 	pm->hook = hooknr;