From 1639b8ba5105542c73e0e1c35e70f245dab89d81 Mon Sep 17 00:00:00 2001
From: Phil Sutter <phil@nwl.cc>
Date: Fri, 21 Feb 2020 13:18:32 +0100
Subject: xtables: Align effect of -4/-6 options with legacy

Legacy iptables doesn't accept -4 or -6 if they don't match the
symlink's native family. The only exception to that is iptables-restore
which simply ignores the lines introduced by non-matching options, which
is useful to create combined dump files for feeding into both
iptables-restore and ip6tables-restore.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 .../tests/shell/testcases/iptables/0006-46-args_0  | 88 ++++++++++++++++++++++
 iptables/xtables.c                                 | 21 ++----
 2 files changed, 96 insertions(+), 13 deletions(-)
 create mode 100755 iptables/tests/shell/testcases/iptables/0006-46-args_0

diff --git a/iptables/tests/shell/testcases/iptables/0006-46-args_0 b/iptables/tests/shell/testcases/iptables/0006-46-args_0
new file mode 100755
index 00000000..17a0a018
--- /dev/null
+++ b/iptables/tests/shell/testcases/iptables/0006-46-args_0
@@ -0,0 +1,88 @@
+#!/bin/bash
+
+RC=0
+
+$XT_MULTI iptables -6 -A FORWARD -j ACCEPT
+rc=$?
+if [[ $rc -ne 2 ]]; then
+	echo "'iptables -6' returned $rc instead of 2"
+	RC=1
+fi
+
+$XT_MULTI ip6tables -4 -A FORWARD -j ACCEPT
+rc=$?
+if [[ $rc -ne 2 ]]; then
+	echo "'ip6tables -4' returned $rc instead of 2"
+	RC=1
+fi
+
+RULESET='*filter
+-4 -A FORWARD -d 10.0.0.1 -j ACCEPT
+-6 -A FORWARD -d fec0:10::1 -j ACCEPT
+COMMIT
+'
+EXPECT4='-P FORWARD ACCEPT
+-A FORWARD -d 10.0.0.1/32 -j ACCEPT'
+EXPECT6='-P FORWARD ACCEPT
+-A FORWARD -d fec0:10::1/128 -j ACCEPT'
+EXPECT_EMPTY='-P FORWARD ACCEPT'
+
+echo "$RULESET" | $XT_MULTI iptables-restore || {
+	echo "iptables-restore failed!"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT4") <($XT_MULTI iptables -S FORWARD) || {
+	echo "unexpected iptables ruleset"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT_EMPTY") <($XT_MULTI ip6tables -S FORWARD) || {
+	echo "unexpected non-empty ip6tables ruleset"
+	RC=1
+}
+
+$XT_MULTI iptables -F FORWARD
+
+echo "$RULESET" | $XT_MULTI ip6tables-restore || {
+	echo "ip6tables-restore failed!"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT6") <($XT_MULTI ip6tables -S FORWARD) || {
+	echo "unexpected ip6tables ruleset"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT_EMPTY") <($XT_MULTI iptables -S FORWARD) || {
+	echo "unexpected non-empty iptables ruleset"
+	RC=1
+}
+
+$XT_MULTI ip6tables -F FORWARD
+
+$XT_MULTI iptables -4 -A FORWARD -d 10.0.0.1 -j ACCEPT || {
+	echo "iptables failed!"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT4") <($XT_MULTI iptables -S FORWARD) || {
+	echo "unexpected iptables ruleset"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT_EMPTY") <($XT_MULTI ip6tables -S FORWARD) || {
+	echo "unexpected non-empty ip6tables ruleset"
+	RC=1
+}
+
+$XT_MULTI iptables -F FORWARD
+
+$XT_MULTI ip6tables -6 -A FORWARD -d fec0:10::1 -j ACCEPT || {
+	echo "ip6tables failed!"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT6") <($XT_MULTI ip6tables -S FORWARD) || {
+	echo "unexpected ip6tables ruleset"
+	RC=1
+}
+diff -u -Z <(echo -e "$EXPECT_EMPTY") <($XT_MULTI iptables -S FORWARD) || {
+	echo "unexpected non-empty iptables ruleset"
+	RC=1
+}
+
+exit $RC
diff --git a/iptables/xtables.c b/iptables/xtables.c
index 8f9dc628..3d75a1dd 100644
--- a/iptables/xtables.c
+++ b/iptables/xtables.c
@@ -917,27 +917,22 @@ void do_parse(struct nft_handle *h, int argc, char *argv[],
 			break;
 
 		case '4':
+			if (args->family == AF_INET)
+				break;
+
 			if (p->restore && args->family == AF_INET6)
 				return;
 
-			if (args->family != AF_INET)
-				exit_tryhelp(2);
-
-			h->ops = nft_family_ops_lookup(args->family);
-			break;
+			exit_tryhelp(2);
 
 		case '6':
+			if (args->family == AF_INET6)
+				break;
+
 			if (p->restore && args->family == AF_INET)
 				return;
 
-			args->family = AF_INET6;
-			xtables_set_nfproto(AF_INET6);
-
-			h->ops = nft_family_ops_lookup(args->family);
-			if (h->ops == NULL)
-				xtables_error(PARAMETER_PROBLEM,
-					      "Unknown family");
-			break;
+			exit_tryhelp(2);
 
 		case 1: /* non option */
 			if (optarg[0] == '!' && optarg[1] == '\0') {
-- 
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