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[NET]: Fix packet timestamping.

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I've found the problem in general.  It affects any 64-bit
architecture.  The problem occurs when you change the system time.

Suppose that when you boot your system clock is forward by a day.
This gets recorded down in skb_tv_base.  You then wind the clock back
by a day.  From that point onwards the offset will be negative which
essentially overflows the 32-bit variables they're stored in.

In fact, why don't we just store the real time stamp in those 32-bit
variables? After all, we're not going to overflow for quite a while
yet.

When we do overflow, we'll need a better solution of course.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu
2005-10-03 13:57:23 -07:00
committed by David S. Miller
parent ddea7be0ec
commit 325ed82393
8 changed files with 15 additions and 26 deletions
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12
include/linux/skbuff.h
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@@ -155,8 +155,6 @@ struct skb_shared_info {
#define SKB_DATAREF_SHIFT 16
#define SKB_DATAREF_MASK ((1 << SKB_DATAREF_SHIFT) - 1)
extern struct timeval skb_tv_base;
struct skb_timeval {
u32 off_sec;
u32 off_usec;
@@ -175,7 +173,7 @@ enum {
* @prev: Previous buffer in list
* @list: List we are on
* @sk: Socket we are owned by
* @tstamp: Time we arrived stored as offset to skb_tv_base
* @tstamp: Time we arrived
* @dev: Device we arrived on/are leaving by
* @input_dev: Device we arrived on
* @h: Transport layer header
@@ -1255,10 +1253,6 @@ static inline void skb_get_timestamp(const struct sk_buff *skb, struct timeval *
{
stamp->tv_sec = skb->tstamp.off_sec;
stamp->tv_usec = skb->tstamp.off_usec;
if (skb->tstamp.off_sec) {
stamp->tv_sec += skb_tv_base.tv_sec;
stamp->tv_usec += skb_tv_base.tv_usec;
}
}
/**
@@ -1272,8 +1266,8 @@ static inline void skb_get_timestamp(const struct sk_buff *skb, struct timeval *
*/
static inline void skb_set_timestamp(struct sk_buff *skb, const struct timeval *stamp)
{
skb->tstamp.off_sec = stamp->tv_sec - skb_tv_base.tv_sec;
skb->tstamp.off_usec = stamp->tv_usec - skb_tv_base.tv_usec;
skb->tstamp.off_sec = stamp->tv_sec;
skb->tstamp.off_usec = stamp->tv_usec;
}
extern void __net_timestamp(struct sk_buff *skb);