xtables: Fix for inserting rule at wrong position

iptables-restore allows to insert rules at a certain position which is
problematic for iptables-nft to realize since rule position is not
determined by number but handle of previous or following rule and in
case the rules surrounding the new one are new as well, they don't have
a handle to refer to yet.

Fix this by making use of NFTNL_RULE_POSITION_ID attribute: When
inserting before a rule which does not have a handle, refer to it using
its NFTNL_RULE_ID value. If the latter doesn't exist either, assign a
new one to it.

The last used rule ID value is tracked in a new field of struct
nft_handle which is incremented before each use.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 176 insertions, 10 deletions

diff --git a/iptables/nft.c b/iptables/nft.c
index ee3d142b..83d373c9 100644
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -2063,16 +2063,30 @@ int nft_rule_delete(struct nft_handle *h, const char *chain,
 static struct nftnl_rule *
 nft_rule_add(struct nft_handle *h, const char *chain,
 	     const char *table, struct iptables_command_state *cs,
-	     uint64_t handle, bool verbose)
+	     struct nftnl_rule *ref, bool verbose)
 {
 	struct nftnl_rule *r;
+	uint64_t ref_id;
 
 	r = nft_rule_new(h, chain, table, cs);
 	if (r == NULL)
 		return NULL;
 
-	if (handle > 0)
-		nftnl_rule_set_u64(r, NFTNL_RULE_POSITION, handle);
+	if (ref) {
+		ref_id = nftnl_rule_get_u64(ref, NFTNL_RULE_HANDLE);
+		if (ref_id > 0) {
+			nftnl_rule_set_u64(r, NFTNL_RULE_POSITION, ref_id);
+			DEBUGP("adding after rule handle %"PRIu64"\n", ref_id);
+		} else {
+			ref_id = nftnl_rule_get_u32(ref, NFTNL_RULE_ID);
+			if (!ref_id) {
+				ref_id = ++h->rule_id;
+				nftnl_rule_set_u32(ref, NFTNL_RULE_ID, ref_id);
+			}
+			nftnl_rule_set_u32(r, NFTNL_RULE_POSITION_ID, ref_id);
+			DEBUGP("adding after rule ID %"PRIu64"\n", ref_id);
+		}
+	}
 
 	if (batch_rule_add(h, NFT_COMPAT_RULE_INSERT, r) < 0) {
 		nftnl_rule_free(r);
@@ -2088,9 +2102,8 @@ nft_rule_add(struct nft_handle *h, const char *chain,
 int nft_rule_insert(struct nft_handle *h, const char *chain,
 		    const char *table, void *data, int rulenum, bool verbose)
 {
-	struct nftnl_rule *r, *new_rule;
+	struct nftnl_rule *r = NULL, *new_rule;
 	struct nftnl_chain *c;
-	uint64_t handle = 0;
 
 	/* If built-in chains don't exist for this table, create them */
 	if (nft_xtables_config_load(h, XTABLES_CONFIG_DEFAULT, 0) < 0)
@@ -2118,16 +2131,13 @@ int nft_rule_insert(struct nft_handle *h, const char *chain,
 			errno = ENOENT;
 			goto err;
 		}
-
-		handle = nftnl_rule_get_u64(r, NFTNL_RULE_HANDLE);
-		DEBUGP("adding after rule handle %"PRIu64"\n", handle);
 	}
 
-	new_rule = nft_rule_add(h, chain, table, data, handle, verbose);
+	new_rule = nft_rule_add(h, chain, table, data, r, verbose);
 	if (!new_rule)
 		goto err;
 
-	if (handle)
+	if (r)
 		nftnl_chain_rule_insert_at(new_rule, r);
 	else
 		nftnl_chain_rule_add(new_rule, c);
diff --git a/iptables/nft.h b/iptables/nft.h
index 97d73c8b..0726923a 100644
--- a/iptables/nft.h
+++ b/iptables/nft.h
@@ -32,6 +32,7 @@ struct nft_handle {
 	struct mnl_socket	*nl;
 	uint32_t		portid;
 	uint32_t		seq;
+	uint32_t		rule_id;
 	struct list_head	obj_list;
 	int			obj_list_num;
 	struct nftnl_batch	*batch;
diff --git a/iptables/tests/shell/testcases/ipt-restore/0003-restore-ordering_0 b/iptables/tests/shell/testcases/ipt-restore/0003-restore-ordering_0
new file mode 100755
index 00000000..51f2422e
--- /dev/null
+++ b/iptables/tests/shell/testcases/ipt-restore/0003-restore-ordering_0
@@ -0,0 +1,117 @@
+#!/bin/bash
+
+# Make sure iptables-restore does the right thing
+# when encountering INSERT rules with index.
+
+set -e
+
+# show rules, drop uninteresting policy settings
+ipt_show() {
+	$XT_MULTI iptables -S | grep -v '^-P'
+}
+
+# basic issue reproducer
+
+$XT_MULTI iptables-restore <<EOF
+*filter
+-A FORWARD -m comment --comment "appended rule" -j ACCEPT
+-I FORWARD 1 -m comment --comment "rule 1" -j ACCEPT
+-I FORWARD 2 -m comment --comment "rule 2" -j ACCEPT
+-I FORWARD 3 -m comment --comment "rule 3" -j ACCEPT
+COMMIT
+EOF
+
+EXPECT='-A FORWARD -m comment --comment "rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "rule 2" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)
+
+# insert rules into existing ruleset
+
+$XT_MULTI iptables-restore --noflush <<EOF
+*filter
+-I FORWARD 1 -m comment --comment "rule 0.5" -j ACCEPT
+-I FORWARD 3 -m comment --comment "rule 1.5" -j ACCEPT
+-I FORWARD 5 -m comment --comment "rule 2.5" -j ACCEPT
+-I FORWARD 7 -m comment --comment "rule 3.5" -j ACCEPT
+-I FORWARD 9 -m comment --comment "appended rule 2" -j ACCEPT
+COMMIT
+EOF
+
+EXPECT='-A FORWARD -m comment --comment "rule 0.5" -j ACCEPT
+-A FORWARD -m comment --comment "rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "rule 1.5" -j ACCEPT
+-A FORWARD -m comment --comment "rule 2" -j ACCEPT
+-A FORWARD -m comment --comment "rule 2.5" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3.5" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule 2" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)
+
+# insert rules in between added ones
+
+$XT_MULTI iptables-restore <<EOF
+*filter
+-A FORWARD -m comment --comment "appended rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule 2" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule 3" -j ACCEPT
+-I FORWARD 1 -m comment --comment "rule 1" -j ACCEPT
+-I FORWARD 3 -m comment --comment "rule 2" -j ACCEPT
+-I FORWARD 5 -m comment --comment "rule 3" -j ACCEPT
+COMMIT
+EOF
+
+EXPECT='-A FORWARD -m comment --comment "rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "rule 2" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule 2" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule 3" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)
+
+# test rule deletion in dump files
+
+$XT_MULTI iptables-restore --noflush <<EOF
+*filter
+-D FORWARD -m comment --comment "appended rule 1" -j ACCEPT
+-D FORWARD 3
+-I FORWARD 3 -m comment --comment "manually replaced rule 2" -j ACCEPT
+COMMIT
+EOF
+
+EXPECT='-A FORWARD -m comment --comment "rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "rule 2" -j ACCEPT
+-A FORWARD -m comment --comment "manually replaced rule 2" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT
+-A FORWARD -m comment --comment "appended rule 3" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)
+
+# test rule replacement in dump files
+
+$XT_MULTI iptables-restore <<EOF
+*filter
+-A FORWARD -m comment --comment "rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "rule to be replaced" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT
+COMMIT
+EOF
+
+$XT_MULTI iptables-restore --noflush <<EOF
+*filter
+-R FORWARD 2 -m comment --comment "replacement" -j ACCEPT
+-I FORWARD 2 -m comment --comment "insert referencing replaced rule" -j ACCEPT
+COMMIT
+EOF
+
+EXPECT='-A FORWARD -m comment --comment "rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "insert referencing replaced rule" -j ACCEPT
+-A FORWARD -m comment --comment replacement -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)
diff --git a/iptables/tests/shell/testcases/iptables/0005-rule-replace_0 b/iptables/tests/shell/testcases/iptables/0005-rule-replace_0
new file mode 100755
index 00000000..5a3e922e
--- /dev/null
+++ b/iptables/tests/shell/testcases/iptables/0005-rule-replace_0
@@ -0,0 +1,38 @@
+#!/bin/bash
+
+# test rule replacement
+
+set -e
+
+# show rules, drop uninteresting policy settings
+ipt_show() {
+	$XT_MULTI iptables -S | grep -v '^-P'
+}
+
+$XT_MULTI iptables -A FORWARD -m comment --comment "rule 1" -j ACCEPT
+$XT_MULTI iptables -A FORWARD -m comment --comment "rule 2" -j ACCEPT
+$XT_MULTI iptables -A FORWARD -m comment --comment "rule 3" -j ACCEPT
+
+$XT_MULTI iptables -R FORWARD 2 -m comment --comment "replaced 2" -j ACCEPT
+
+EXPECT='-A FORWARD -m comment --comment "rule 1" -j ACCEPT
+-A FORWARD -m comment --comment "replaced 2" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)
+
+$XT_MULTI iptables -R FORWARD 1 -m comment --comment "replaced 1" -j ACCEPT
+
+EXPECT='-A FORWARD -m comment --comment "replaced 1" -j ACCEPT
+-A FORWARD -m comment --comment "replaced 2" -j ACCEPT
+-A FORWARD -m comment --comment "rule 3" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)
+
+$XT_MULTI iptables -R FORWARD 3 -m comment --comment "replaced 3" -j ACCEPT
+
+EXPECT='-A FORWARD -m comment --comment "replaced 1" -j ACCEPT
+-A FORWARD -m comment --comment "replaced 2" -j ACCEPT
+-A FORWARD -m comment --comment "replaced 3" -j ACCEPT'
+
+diff -u -Z <(echo -e "$EXPECT") <(ipt_show)