Re: Linux 2.6.9-rc1

[Harald Welte <laforge@netfilter.org>]

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On Wed, Aug 25, 2004 at 11:52:30AM -0700, Joshua Kwan wrote:
> Linus Torvalds wrote:
> >Harald Welte:
> ...
> >  o [NETFILTER]: Make 'helper' list of ip_nat_core static
> ...
> 
> I suspect that this changeset[1] somehow caused this to happen (many 
> times) in dmesg:
> 
> ASSERT net/ipv4/netfilter/ip_nat_helper.c:428 &ip_nat_lock writelocked

yes, indeed.

> It seems to be working properly (NATting two machines behind a local 
> network to the Internet.)

The 'problem' is that we try to get a readlock while we're already
protected under a write lock.

Please see the following [quite trivial, but yet untested] patch:

--- linux-2.6.9-rc1/net/ipv4/netfilter/ip_nat_core.c	2004-08-25 22:22:36.450340504 +0200
+++ linux-2.6.9-rc1-find_helper/net/ipv4/netfilter/ip_nat_core.c	2004-08-25 22:28:37.668273271 +0200
@@ -635,7 +635,7 @@
 
 	/* If there's a helper, assign it; based on new tuple. */
 	if (!conntrack->master)
-		info->helper = ip_nat_find_helper(&reply);
+		info->helper = __ip_nat_find_helper(&reply);
 
 	/* It's done. */
 	info->initialized |= (1 << HOOK2MANIP(hooknum));
--- linux-2.6.9-rc1/net/ipv4/netfilter/ip_nat_helper.c	2004-08-25 22:22:36.453340376 +0200
+++ linux-2.6.9-rc1-find_helper/net/ipv4/netfilter/ip_nat_helper.c	2004-08-25 22:27:47.880335112 +0200
@@ -421,12 +421,18 @@
 }
 
 struct ip_nat_helper *
+__ip_nat_find_helper(const struct ip_conntrack_tuple *tuple)
+{
+	return LIST_FIND(&helpers, helper_cmp, struct ip_nat_helper *, tuple);
+}
+
+struct ip_nat_helper *
 ip_nat_find_helper(const struct ip_conntrack_tuple *tuple)
 {
 	struct ip_nat_helper *h;
 
 	READ_LOCK(&ip_nat_lock);
-	h = LIST_FIND(&helpers, helper_cmp, struct ip_nat_helper *, tuple);
+	h = __ip_nat_find_helper(tuple);
 	READ_UNLOCK(&ip_nat_lock);
 
 	return h;
--- linux-2.6.9-rc1/net/ipv4/netfilter/ip_nat_standalone.c	2004-08-25 22:22:36.461340035 +0200
+++ linux-2.6.9-rc1-find_helper/net/ipv4/netfilter/ip_nat_standalone.c	2004-08-25 22:29:30.047102589 +0200
@@ -394,4 +394,5 @@
 EXPORT_SYMBOL(ip_nat_mangle_tcp_packet);
 EXPORT_SYMBOL(ip_nat_mangle_udp_packet);
 EXPORT_SYMBOL(ip_nat_used_tuple);
+EXPORT_SYMBOL(ip_nat_find_helper);
 MODULE_LICENSE("GPL");

-- 
- Harald Welte <laforge@netfilter.org>             http://www.netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie

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