From: Stephen Hemminger <shemminger@vyatta•com>
To: 王韬（计算机科学学院） <wtweeker@163•com>
Cc: akpm@linux-foundation•org, bugzilla-daemon@bugzilla•kernel.org,
bugme-daemon@bugzilla•kernel.org, netdev@vger•kernel.org,
Patrick McHardy <kaber@trash•net>,
kaber@trash•net
Subject: Re: [Bugme-new] [Bug 17622] New: snmp trap ALG issue
Date: Thu, 16 Sep 2010 22:39:09 -0700 [thread overview]
Message-ID: <20100916223909.68e5c557@nehalam> (raw)
In-Reply-To: <6029e4.25bb.12b1d97358d.Coremail.wtweeker@163.com>
I think the bug should be fixed by removing the potentially buggy
fast_csum() in nf_nat_snmp_basic and just using the existing
generic code. The following is compile tested only..
Subject: [PATCH] nf_nat_snmp: use existing checksum update code
The fast_csum() in NAT code for processing SNMP trap is buggy
(see https://bugzilla.kernel.org/show_bug.cgi?id=17622)
Replace it by using the existing checksum replacement code;
it means adding a new csum_replace1() inline wrapper.
Signed-off-by: Stephen Hemminger <shemminger@vyatta•com>
---
include/net/checksum.h | 5 +++++
net/ipv4/netfilter/nf_nat_snmp_basic.c | 31 ++-----------------------------
2 files changed, 7 insertions(+), 29 deletions(-)
--- a/net/ipv4/netfilter/nf_nat_snmp_basic.c 2010-09-16 22:17:21.660806917 -0700
+++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c 2010-09-16 22:32:52.084075112 -0700
@@ -882,30 +882,6 @@ static unsigned char snmp_request_decode
}
/*
- * Fast checksum update for possibly oddly-aligned UDP byte, from the
- * code example in the draft.
- */
-static void fast_csum(__sum16 *csum,
- const unsigned char *optr,
- const unsigned char *nptr,
- int offset)
-{
- unsigned char s[4];
-
- if (offset & 1) {
- s[0] = s[2] = 0;
- s[1] = ~*optr;
- s[3] = *nptr;
- } else {
- s[1] = s[3] = 0;
- s[0] = ~*optr;
- s[2] = *nptr;
- }
-
- *csum = csum_fold(csum_partial(s, 4, ~csum_unfold(*csum)));
-}
-
-/*
* Mangle IP address.
* - begin points to the start of the snmp messgae
* - addr points to the start of the address
@@ -924,11 +900,8 @@ static inline void mangle_address(unsign
*addr = map->to;
/* Update UDP checksum if being used */
- if (*check) {
- fast_csum(check,
- &map->from, &map->to, addr - begin);
-
- }
+ if (*check)
+ csum_replace1(check, map->from, map->to);
if (debug)
printk(KERN_DEBUG "bsalg: mapped %pI4 to %pI4\n",
--- a/include/net/checksum.h 2010-09-16 22:31:27.524503074 -0700
+++ b/include/net/checksum.h 2010-09-16 22:32:09.934282263 -0700
@@ -106,6 +106,11 @@ static inline void csum_replace2(__sum16
csum_replace4(sum, (__force __be32)from, (__force __be32)to);
}
+static inline void csum_replace1(__sum16 *sum, __u8 from, __u8 to)
+{
+ csum_replace4(sum, (__force __be32)from, (__force __be32)to);
+}
+
struct sk_buff;
extern void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
__be32 from, __be32 to, int pseudohdr);
next prev parent reply other threads:[~2010-09-17 5:39 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-17622-10286@https.bugzilla.kernel.org/>
2010-09-14 23:32 ` [Bugme-new] [Bug 17622] New: snmp trap ALG issue Andrew Morton
[not found] ` <6029e4.25bb.12b1d97358d.Coremail.wtweeker@163.com>
2010-09-17 5:39 ` Stephen Hemminger [this message]
2010-09-17 12:08 ` Patrick McHardy
2010-09-17 15:31 ` Stephen Hemminger
2010-09-17 15:36 ` Patrick McHardy
[not found] ` <2a014b7c.92ce.12b293c61ba.Coremail.wtweeker@163.com>
2010-09-20 16:44 ` [PATCH] nf_nat_snmp: fix checksum calculation (v3) Stephen Hemminger
2010-09-20 17:35 ` Patrick McHardy
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