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Iterate lists from the tail to the head

PATCH Applied Pablo Neira 2 participants 2 messages Aug 5, 2005

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Pablo Neira

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#0 lore raw

PATCH 1/1 Iterate lists from the tail to the head

Currently conntracks are inserted after the head. That means that conntracks are sorted from the biggest to the smallest id. This happens because we use list_prepend (list_add) instead list_add_tail. This can result in problems during the list iteration.

                list_for_each(i, &ip_conntrack_hash[cb->args[0]]) {
                        h = (struct ip_conntrack_tuple_hash *) i;
                        if (DIRECTION(h) != IP_CT_DIR_ORIGINAL)
                                continue;
                        ct = tuplehash_to_ctrack(h);
                        if (ct->id <= *id)
                                continue;

In that case just the first conntrack in the bucket will be dumped. To fix this, we iterate the list from the tail to the head via list_for_each_prev. Same thing for the list of expectations.

Signed-off-by Pablo Neira Ayuso <[email protected]>
net/ipv4/netfilter/ip_conntrack_netlink.c +3 -3
Index: netfilter-2.6.14/net/ipv4/netfilter/ip_conntrack_netlink.c
===================================================================
@@ -404,7 +404,7 @@
 
 	read_lock_bh(&ip_conntrack_lock);
 	for (; cb->args[0] < ip_conntrack_htable_size; cb->args[0]++, *id = 0) {
-		list_for_each(i, &ip_conntrack_hash[cb->args[0]]) {
+		list_for_each_prev(i, &ip_conntrack_hash[cb->args[0]]) {
 			h = (struct ip_conntrack_tuple_hash *) i;
 			if (DIRECTION(h) != IP_CT_DIR_ORIGINAL)
 				continue;

@@ -441,7 +441,7 @@
 
 	write_lock_bh(&ip_conntrack_lock);
 	for (; cb->args[0] < ip_conntrack_htable_size; cb->args[0]++, *id = 0) {
-		list_for_each(i, &ip_conntrack_hash[cb->args[0]]) {
+		list_for_each_prev(i, &ip_conntrack_hash[cb->args[0]]) {
 			h = (struct ip_conntrack_tuple_hash *) i;
 			if (DIRECTION(h) != IP_CT_DIR_ORIGINAL)
 				continue;

@@ -1214,7 +1214,7 @@
 	DEBUGP("entered %s, last id=%llu\n", __FUNCTION__, *id);
 
 	read_lock_bh(&ip_conntrack_lock);
-	list_for_each(i, &ip_conntrack_expect_list) {
+	list_for_each_prev(i, &ip_conntrack_expect_list) {
 		exp = (struct ip_conntrack_expect *) i;
 		if (exp->id <= *id)
 			continue;
Applied
#1 lore raw
Quoted 4 lines · Pablo Neira

Currently conntracks are inserted after the head. That means that conntracks are sorted from the biggest to the smallest id. This happens because we use list_prepend (list_add) instead list_add_tail. This can result in problems during the list iteration.

thanks, applied.

Signature · 5 lines
- Harald Welte <[email protected]>                 http://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