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[NETFILTER]: xt_connbytes: fix division by zero 

When the packet counter of a connection is zero a division by zero
occurs in div64_64(). Fix that by using zero as average value, which
is correct as long as the packet counter didn't overflow, at which
point we have lost anyway.

Additionally we're probably going to go back to 64 bit counters
in 2.6.21.

Based on patch from Jonas Berlin <xkr47@outerspace.dyndns.org>,
with suggestions from KOVACS Krisztian <hidden@balabit.hu>.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy 2007-01-30 14:24:29 -08:00 committed by David S. Miller
parent 24a1dec550
commit fb74a84160
1 changed files with 12 additions and 17 deletions
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29
net/netfilter/xt_connbytes.c
View File

@ -52,6 +52,8 @@ match(const struct sk_buff *skb,
{
const struct xt_connbytes_info *sinfo = matchinfo;
u_int64_t what = 0; /* initialize to make gcc happy */
u_int64_t bytes = 0;
u_int64_t pkts = 0;
const struct ip_conntrack_counter *counters;
if (!(counters = nf_ct_get_counters(skb)))
@ -89,29 +91,22 @@ match(const struct sk_buff *skb,
case XT_CONNBYTES_AVGPKT:
switch (sinfo->direction) {
case XT_CONNBYTES_DIR_ORIGINAL:
what = div64_64(counters[IP_CT_DIR_ORIGINAL].bytes,
counters[IP_CT_DIR_ORIGINAL].packets);
bytes = counters[IP_CT_DIR_ORIGINAL].bytes;
pkts = counters[IP_CT_DIR_ORIGINAL].packets;
break;
case XT_CONNBYTES_DIR_REPLY:
what = div64_64(counters[IP_CT_DIR_REPLY].bytes,
counters[IP_CT_DIR_REPLY].packets);
bytes = counters[IP_CT_DIR_REPLY].bytes;
pkts = counters[IP_CT_DIR_REPLY].packets;
break;
case XT_CONNBYTES_DIR_BOTH:
{
u_int64_t bytes;
u_int64_t pkts;
bytes = counters[IP_CT_DIR_ORIGINAL].bytes +
counters[IP_CT_DIR_REPLY].bytes;
pkts = counters[IP_CT_DIR_ORIGINAL].packets+
counters[IP_CT_DIR_REPLY].packets;
/* FIXME_THEORETICAL: what to do if sum
* overflows ? */
what = div64_64(bytes, pkts);
}
bytes = counters[IP_CT_DIR_ORIGINAL].bytes +
counters[IP_CT_DIR_REPLY].bytes;
pkts = counters[IP_CT_DIR_ORIGINAL].packets +
counters[IP_CT_DIR_REPLY].packets;
break;
}
if (pkts != 0)
what = div64_64(bytes, pkts);
break;
}