From e1ccd979e6849748578fad76475c688bdd16df0d Mon Sep 17 00:00:00 2001
From: Florian Westphal <fw@strlen.de>
Date: Tue, 10 Sep 2019 23:10:59 +0200
Subject: ebtables: fix over-eager -o checks on custom chains

Arturo reports ebtables-nft reports an error when -o is
used in custom chains:

-A MYCHAIN -o someif
makes ebtables-nft exit with an error:
"Use -o only in OUTPUT, FORWARD and POSTROUTING chains."

Problem is that all the "-o" checks expect <= NF_BR_POST_ROUTING
to mean "builtin", so -1 mistakenly leads to the checks being active.

Reported-by: Arturo Borrero Gonzalez <arturo@netfilter.org>
Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1347
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 extensions/libebt_standard.t                        | 17 +++++++++++++++++
 .../shell/testcases/ebtables/0005-ifnamechecks_0    | 21 +++++++++++++++++++++
 iptables/xtables-eb.c                               |  5 +++--
 3 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100755 iptables/tests/shell/testcases/ebtables/0005-ifnamechecks_0

diff --git a/extensions/libebt_standard.t b/extensions/libebt_standard.t
index 0d678fb2..c6c31727 100644
--- a/extensions/libebt_standard.t
+++ b/extensions/libebt_standard.t
@@ -9,3 +9,20 @@
 -p ! ARP -j ACCEPT;=;OK
 -p 0 -j ACCEPT;=;FAIL
 -p ! 0 -j ACCEPT;=;FAIL
+:INPUT
+-i foobar;=;OK
+-o foobar;=;FAIL
+:FORWARD
+-i foobar;=;OK
+-o foobar;=;OK
+:OUTPUT
+-i foobar;=;FAIL
+-o foobar;=;OK
+:PREROUTING
+*nat
+-i foobar;=;OK
+-o foobar;=;FAIL
+:POSTROUTING
+*nat
+-i foobar;=;FAIL
+-o foobar;=;OK
diff --git a/iptables/tests/shell/testcases/ebtables/0005-ifnamechecks_0 b/iptables/tests/shell/testcases/ebtables/0005-ifnamechecks_0
new file mode 100755
index 00000000..2163d364
--- /dev/null
+++ b/iptables/tests/shell/testcases/ebtables/0005-ifnamechecks_0
@@ -0,0 +1,21 @@
+#!/bin/bash
+
+set -e
+
+# there is no legacy backend to test
+[[ $XT_MULTI == */xtables-nft-multi ]] || { echo "skip $XT_MULTI"; exit 0; }
+
+EXPECT='*filter
+:INPUT ACCEPT
+:FORWARD ACCEPT
+:OUTPUT ACCEPT
+:PVEFW-FORWARD ACCEPT
+:PVEFW-FWBR-OUT ACCEPT
+-A FORWARD -j PVEFW-FORWARD
+-A PVEFW-FORWARD -p IPv4 -j ACCEPT
+-A PVEFW-FORWARD -p IPv6 -j ACCEPT
+-A PVEFW-FORWARD -i fwln+ -j ACCEPT
+-A PVEFW-FORWARD -o fwln+ -j PVEFW-FWBR-OUT'
+
+$XT_MULTI ebtables-restore <<<$EXPECT
+exec diff -u <(echo -e "$EXPECT") <($XT_MULTI ebtables-save | grep -v '^#')
diff --git a/iptables/xtables-eb.c b/iptables/xtables-eb.c
index 121ecbec..3b03daef 100644
--- a/iptables/xtables-eb.c
+++ b/iptables/xtables-eb.c
@@ -197,7 +197,8 @@ int ebt_get_current_chain(const char *chain)
 	else if (strcmp(chain, "POSTROUTING") == 0)
 		return NF_BR_POST_ROUTING;
 
-	return -1;
+	/* placeholder for user defined chain */
+	return NF_BR_NUMHOOKS;
 }
 
 /*
@@ -1223,7 +1224,7 @@ print_zero:
 	cs.eb.ethproto = htons(cs.eb.ethproto);
 
 	if (command == 'P') {
-		if (selected_chain < 0) {
+		if (selected_chain >= NF_BR_NUMHOOKS) {
 			ret = ebt_set_user_chain_policy(h, *table, chain, policy);
 		} else {
 			if (strcmp(policy, "RETURN") == 0) {
-- 
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