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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 <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Herbert Xu 2005-10-03 13:57:23 -07:00 • committed by David S. Miller
commit 325ed82393
8 changed files with 15 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

5
net/core/skbuff.c
View file

@ -71,8 +71,6 @@
static kmem_cache_t *skbuff_head_cache __read_mostly;
static kmem_cache_t *skbuff_fclone_cache __read_mostly;
struct timeval __read_mostly skb_tv_base;
/*
* Keep out-of-line to prevent kernel bloat.
* __builtin_return_address is not used because it is not always
@ -1708,8 +1706,6 @@ void __init skb_init(void)
NULL, NULL);
if (!skbuff_fclone_cache)
panic("cannot create skbuff cache");
do_gettimeofday(&skb_tv_base);
}
EXPORT_SYMBOL(___pskb_trim);
@ -1743,4 +1739,3 @@ EXPORT_SYMBOL(skb_prepare_seq_read);
EXPORT_SYMBOL(skb_seq_read);
EXPORT_SYMBOL(skb_abort_seq_read);
EXPORT_SYMBOL(skb_find_text);
EXPORT_SYMBOL(skb_tv_base);

4
net/ipv4/netfilter/ip_queue.c
View file

@ -240,8 +240,8 @@ ipq_build_packet_message(struct ipq_queue_entry *entry, int *errp)
pmsg->packet_id = (unsigned long )entry;
pmsg->data_len = data_len;
pmsg->timestamp_sec = skb_tv_base.tv_sec + entry->skb->tstamp.off_sec;
pmsg->timestamp_usec = skb_tv_base.tv_usec + entry->skb->tstamp.off_usec;
pmsg->timestamp_sec = entry->skb->tstamp.off_sec;
pmsg->timestamp_usec = entry->skb->tstamp.off_usec;
pmsg->mark = entry->skb->nfmark;
pmsg->hook = entry->info->hook;
pmsg->hw_protocol = entry->skb->protocol;

4
net/ipv4/netfilter/ipt_ULOG.c
View file

@ -225,8 +225,8 @@ static void ipt_ulog_packet(unsigned int hooknum,
/* copy hook, prefix, timestamp, payload, etc. */
pm->data_len = copy_len;
pm->timestamp_sec = skb_tv_base.tv_sec + skb->tstamp.off_sec;
pm->timestamp_usec = skb_tv_base.tv_usec + skb->tstamp.off_usec;
pm->timestamp_sec = skb->tstamp.off_sec;
pm->timestamp_usec = skb->tstamp.off_usec;
pm->mark = skb->nfmark;
pm->hook = hooknum;
if (prefix != NULL)

4
net/ipv6/netfilter/ip6_queue.c
View file

@ -238,8 +238,8 @@ ipq_build_packet_message(struct ipq_queue_entry *entry, int *errp)
pmsg->packet_id = (unsigned long )entry;
pmsg->data_len = data_len;
pmsg->timestamp_sec = skb_tv_base.tv_sec + entry->skb->tstamp.off_sec;
pmsg->timestamp_usec = skb_tv_base.tv_usec + entry->skb->tstamp.off_usec;
pmsg->timestamp_sec = entry->skb->tstamp.off_sec;
pmsg->timestamp_usec = entry->skb->tstamp.off_usec;
pmsg->mark = entry->skb->nfmark;
pmsg->hook = entry->info->hook;
pmsg->hw_protocol = entry->skb->protocol;

4
net/netfilter/nfnetlink_log.c
View file

@ -494,8 +494,8 @@ __build_packet_message(struct nfulnl_instance *inst,
if (skb->tstamp.off_sec) {
struct nfulnl_msg_packet_timestamp ts;
ts.sec = cpu_to_be64(skb_tv_base.tv_sec + skb->tstamp.off_sec);
ts.usec = cpu_to_be64(skb_tv_base.tv_usec + skb->tstamp.off_usec);
ts.sec = cpu_to_be64(skb->tstamp.off_sec);
ts.usec = cpu_to_be64(skb->tstamp.off_usec);
NFA_PUT(inst->skb, NFULA_TIMESTAMP, sizeof(ts), &ts);
}

4
net/netfilter/nfnetlink_queue.c
View file

@ -492,8 +492,8 @@ nfqnl_build_packet_message(struct nfqnl_instance *queue,
if (entry->skb->tstamp.off_sec) {
struct nfqnl_msg_packet_timestamp ts;
ts.sec = cpu_to_be64(skb_tv_base.tv_sec + entry->skb->tstamp.off_sec);
ts.usec = cpu_to_be64(skb_tv_base.tv_usec + entry->skb->tstamp.off_usec);
ts.sec = cpu_to_be64(entry->skb->tstamp.off_sec);
ts.usec = cpu_to_be64(entry->skb->tstamp.off_usec);
NFA_PUT(skb, NFQA_TIMESTAMP, sizeof(ts), &ts);
}

4
net/packet/af_packet.c
View file

@ -654,8 +654,8 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
__net_timestamp(skb);
sock_enable_timestamp(sk);
}
h->tp_sec = skb_tv_base.tv_sec + skb->tstamp.off_sec;
h->tp_usec = skb_tv_base.tv_usec + skb->tstamp.off_usec;
h->tp_sec = skb->tstamp.off_sec;
h->tp_usec = skb->tstamp.off_usec;
sll = (struct sockaddr_ll*)((u8*)h + TPACKET_ALIGN(sizeof(*h)));
sll->sll_halen = 0;