[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, 10 insertions, 5 deletions

diff --git a/net/compat.c b/net/compat.c
index 1f32866..17c2710 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -545,15 +545,20 @@ int compat_sock_get_timestamp(struct sock *sk, struct timeval __user *userstamp)
 	struct compat_timeval __user *ctv =
 			(struct compat_timeval __user*) userstamp;
 	int err = -ENOENT;
+	struct timeval tv;
 
 	if (!sock_flag(sk, SOCK_TIMESTAMP))
 		sock_enable_timestamp(sk);
-	if (sk->sk_stamp.tv_sec == -1)
+	tv = ktime_to_timeval(sk->sk_stamp);
+	if (tv.tv_sec == -1)
 		return err;
-	if (sk->sk_stamp.tv_sec == 0)
-		do_gettimeofday(&sk->sk_stamp);
-	if (put_user(sk->sk_stamp.tv_sec, &ctv->tv_sec) ||
-			put_user(sk->sk_stamp.tv_usec, &ctv->tv_usec))
+	if (tv.tv_sec == 0) {
+		sk->sk_stamp = ktime_get_real();
+		tv = ktime_to_timeval(sk->sk_stamp);
+	}
+	err = 0;
+	if (put_user(tv.tv_sec, &ctv->tv_sec) ||
+			put_user(tv.tv_usec, &ctv->tv_usec))
 		err = -EFAULT;
 	return err;
 }