[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, 4 insertions, 15 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)