[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>

2 files changed, 13 insertions, 22 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 4dc93cc4d5b7..582db646cc54 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1031,23 +1031,12 @@ void net_disable_timestamp(void)
         atomic_dec(&netstamp_needed);
 }
 
-void __net_timestamp(struct sk_buff *skb)
-{
-        struct timeval tv;
-
-        do_gettimeofday(&tv);
-        skb_set_timestamp(skb, &tv);
-}
-EXPORT_SYMBOL(__net_timestamp);
-
 static inline void net_timestamp(struct sk_buff *skb)
 {
         if (atomic_read(&netstamp_needed))
                 __net_timestamp(skb);
-        else {
-                skb->tstamp.off_sec = 0;
-                skb->tstamp.off_usec = 0;
-        }
+        else
+                skb->tstamp.tv64 = 0;
 }
 
 /*
@@ -1577,7 +1566,7 @@ int netif_rx(struct sk_buff *skb)
         if (netpoll_rx(skb))
                 return NET_RX_DROP;
 
-        if (!skb->tstamp.off_sec)
+        if (!skb->tstamp.tv64)
                 net_timestamp(skb);
 
         /*
@@ -1769,7 +1758,7 @@ int netif_receive_skb(struct sk_buff *skb)
         if (skb->dev->poll && netpoll_rx(skb))
                 return NET_RX_DROP;
 
-        if (!skb->tstamp.off_sec)
+        if (!skb->tstamp.tv64)
                 net_timestamp(skb);
 
         if (!skb->iif)
diff --git a/net/core/sock.c b/net/core/sock.c
index 6d35d5775ba8..6ddb3664b993 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1512,8 +1512,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
         sk->sk_rcvtimeo         =       MAX_SCHEDULE_TIMEOUT;
         sk->sk_sndtimeo         =       MAX_SCHEDULE_TIMEOUT;
 
-        sk->sk_stamp.tv_sec     = -1L;
-        sk->sk_stamp.tv_usec    = -1L;
+        sk->sk_stamp = ktime_set(-1L, -1L);
 
         atomic_set(&sk->sk_refcnt, 1);
 }
@@ -1554,14 +1553,17 @@ EXPORT_SYMBOL(release_sock);
 
 int sock_get_timestamp(struct sock *sk, struct timeval __user *userstamp)
 {
+        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 -ENOENT;
-        if (sk->sk_stamp.tv_sec == 0)
-                do_gettimeofday(&sk->sk_stamp);
-        return copy_to_user(userstamp, &sk->sk_stamp, sizeof(struct timeval)) ?
-                -EFAULT : 0;
+        if (tv.tv_sec == 0) {
+                sk->sk_stamp = ktime_get_real();
+                tv = ktime_to_timeval(sk->sk_stamp);
+        }
+        return copy_to_user(userstamp, &tv, sizeof(tv)) ? -EFAULT : 0;
 }
 EXPORT_SYMBOL(sock_get_timestamp);