[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 <[email protected]>
CC: Stephen Hemminger <[email protected]>
CC: John find <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

net/ipx/af_ipx.c

@@ -1807,8 +1807,8 @@ static int ipx_recvmsg(struct kiocb *iocb, struct socket *sock,
 				     copied);
 	if (rc)
 		goto out_free;
-	if (skb->tstamp.off_sec)
-		skb_get_timestamp(skb, &sk->sk_stamp);
+	if (skb->tstamp.tv64)
+		sk->sk_stamp = skb->tstamp;
 
 	msg->msg_namelen = sizeof(*sipx);