[PATCH] Re: Fw: PROBLEM: Conntrack/NAT bug

From: Harald Welte (laforge@gnumonks.org)
Date: Mon Oct 14 2002 - 06:47:35 EST

On Thu, Oct 10, 2002 at 06:20:46AM -0700, Tom Lanyon wrote:

> [1.] One line summary of the problem: Some sort of coding problem in
> conntrack.

It's not a bug in the code, it's a bug in the debugging ASSERT macros, as
correctly pointed out by Martin Josefsson.

The issue is that we are nesting readlocks, because ip_ct_find_proto()
grabs itself a readlock on ip_conntrack_lock.

The patch below now exports the non-locking __ip_ct_find_proto() function,
thus no more grabbing a nested readlock.

I wanted to go for a different solution, since exporting __ functions is
not exactly clean coding style - but due to the circumstances other solutions
look even more ugly.

Dave, please apply the following fix (again by Martin Josefsson), Thanks.

diff -x '*.orig' -urN linux-2.4.20-pre8-ac3.orig/include/linux/netfilter_ipv4/ip_conntrack_core.h linux-2.4.20-pre8-ac3/include/linux/netfilter_ipv4/ip_conntrack_core.h
--- linux-2.4.20-pre8-ac3.orig/include/linux/netfilter_ipv4/ip_conntrack_core.h 2002-10-10 15:41:55.000000000 +0200
+++ linux-2.4.20-pre8-ac3/include/linux/netfilter_ipv4/ip_conntrack_core.h 2002-10-10 16:07:16.000000000 +0200
@@ -17,7 +17,7 @@
 struct ip_conntrack_protocol;
 extern struct ip_conntrack_protocol *ip_ct_find_proto(u_int8_t protocol);
 /* Like above, but you already have conntrack read lock. */
-extern struct ip_conntrack_protocol *__find_proto(u_int8_t protocol);
+extern struct ip_conntrack_protocol *__ip_ct_find_proto(u_int8_t protocol);
 extern struct list_head protocol_list;
 
 /* Returns conntrack if it dealt with ICMP, and filled in skb->nfct */
diff -x '*.orig' -urN linux-2.4.20-pre8-ac3.orig/net/ipv4/netfilter/ip_conntrack_core.c linux-2.4.20-pre8-ac3/net/ipv4/netfilter/ip_conntrack_core.c
--- linux-2.4.20-pre8-ac3.orig/net/ipv4/netfilter/ip_conntrack_core.c 2002-10-10 15:41:57.000000000 +0200
+++ linux-2.4.20-pre8-ac3/net/ipv4/netfilter/ip_conntrack_core.c 2002-10-10 16:07:16.000000000 +0200
@@ -74,7 +74,7 @@
         return protocol == curr->proto;
 }
 
-struct ip_conntrack_protocol *__find_proto(u_int8_t protocol)
+struct ip_conntrack_protocol *__ip_ct_find_proto(u_int8_t protocol)
 {
         struct ip_conntrack_protocol *p;
 
@@ -92,7 +92,7 @@
         struct ip_conntrack_protocol *p;
 
         READ_LOCK(&ip_conntrack_lock);
- p = __find_proto(protocol);
+ p = __ip_ct_find_proto(protocol);
         READ_UNLOCK(&ip_conntrack_lock);
         return p;
 }
diff -x '*.orig' -urN linux-2.4.20-pre8-ac3.orig/net/ipv4/netfilter/ip_conntrack_standalone.c linux-2.4.20-pre8-ac3/net/ipv4/netfilter/ip_conntrack_standalone.c
--- linux-2.4.20-pre8-ac3.orig/net/ipv4/netfilter/ip_conntrack_standalone.c 2002-10-10 15:41:57.000000000 +0200
+++ linux-2.4.20-pre8-ac3/net/ipv4/netfilter/ip_conntrack_standalone.c 2002-10-10 16:07:16.000000000 +0200
@@ -71,7 +71,7 @@
         len += sprintf(buffer + len, "use=%u proto=%u ",
                       atomic_read(&expect->use), expect->tuple.dst.protonum);
         len += print_tuple(buffer + len, &expect->tuple,
- __find_proto(expect->tuple.dst.protonum));
+ __ip_ct_find_proto(expect->tuple.dst.protonum));
         len += sprintf(buffer + len, "\n");
         return len;
 }
@@ -81,7 +81,7 @@
 {
         unsigned int len;
         struct ip_conntrack_protocol *proto
- = __find_proto(conntrack->tuplehash[IP_CT_DIR_ORIGINAL]
+ = __ip_ct_find_proto(conntrack->tuplehash[IP_CT_DIR_ORIGINAL]
                                .tuple.dst.protonum);
 
         len = sprintf(buffer, "%-8s %u %lu ",
@@ -361,6 +361,7 @@
 EXPORT_SYMBOL(ip_ct_selective_cleanup);
 EXPORT_SYMBOL(ip_ct_refresh);
 EXPORT_SYMBOL(ip_ct_find_proto);
+EXPORT_SYMBOL(__ip_ct_find_proto);
 EXPORT_SYMBOL(ip_ct_find_helper);
 EXPORT_SYMBOL(ip_conntrack_expect_related);
 EXPORT_SYMBOL(ip_conntrack_change_expect);
diff -x '*.orig' -urN linux-2.4.20-pre8-ac3.orig/net/ipv4/netfilter/ip_nat_core.c linux-2.4.20-pre8-ac3/net/ipv4/netfilter/ip_nat_core.c
--- linux-2.4.20-pre8-ac3.orig/net/ipv4/netfilter/ip_nat_core.c 2002-10-10 16:10:49.000000000 +0200
+++ linux-2.4.20-pre8-ac3/net/ipv4/netfilter/ip_nat_core.c 2002-10-10 16:10:36.000000000 +0200
@@ -739,7 +739,7 @@
         int ret = 1;
 
         MUST_BE_READ_LOCKED(&ip_conntrack_lock);
- proto = ip_ct_find_proto((*pskb)->nh.iph->protocol);
+ proto = __ip_ct_find_proto((*pskb)->nh.iph->protocol);
         if (proto->exp_matches_pkt)
                 ret = proto->exp_matches_pkt(exp, pskb);
 

> Thanks for your help

Thanks for your help (i mean it!).

> Tom Lanyon
> toml@internode.on.net 

-- 
Live long and prosper
- Harald Welte / laforge@gnumonks.org               http://www.gnumonks.org/
============================================================================
"If this were a dictatorship, it'd be a heck of a lot easier, just so long
 as I'm the dictator."  --  George W. Bush Dec 18, 2000
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