[PATCH iptables-nftables] nft: fix interface wildcard matching

[Pablo Neira Ayuso <pablo@netfilter.org>]

In (73ea1cc nft: convert rule into a command state structure), the
interface wildcard matching got broken. The previous handling was
flawed by the use of ifnametoindex in scenario where the interface
may vanished after a rule was added.

This approach relies on the trailing '\0' to identify if this is
an exact or wildcard matching, based on discussion with Florian.

Based on initial patch from Anand Raj Manickam.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 iptables/nft-shared.c |   38 ++++++++++++++++----------------------
 1 file changed, 16 insertions(+), 22 deletions(-)

diff --git a/iptables/nft-shared.c b/iptables/nft-shared.c
index 3987f74..e0eaa17 100644
--- a/iptables/nft-shared.c
+++ b/iptables/nft-shared.c
@@ -124,13 +124,11 @@ void add_iniface(struct nft_rule *r, char *iface, int invflags)
 	else
 		op = NFT_CMP_EQ;
 
-	if (iface[iface_len - 1] == '+') {
-		add_meta(r, NFT_META_IIFNAME);
+	add_meta(r, NFT_META_IIFNAME);
+	if (iface[iface_len - 1] == '+')
 		add_cmp_ptr(r, op, iface, iface_len - 1);
-	} else {
-		add_meta(r, NFT_META_IIF);
-		add_cmp_u32(r, if_nametoindex(iface), op);
-	}
+	else
+		add_cmp_ptr(r, op, iface, iface_len + 1);
 }
 
 void add_outiface(struct nft_rule *r, char *iface, int invflags)
@@ -145,13 +143,11 @@ void add_outiface(struct nft_rule *r, char *iface, int invflags)
 	else
 		op = NFT_CMP_EQ;
 
-	if (iface[iface_len - 1] == '+') {
-		add_meta(r, NFT_META_OIFNAME);
+	add_meta(r, NFT_META_OIFNAME);
+	if (iface[iface_len - 1] == '+')
 		add_cmp_ptr(r, op, iface, iface_len - 1);
-	} else {
-		add_meta(r, NFT_META_OIF);
-		add_cmp_u32(r, if_nametoindex(iface), op);
-	}
+	else
+		add_cmp_ptr(r, op, iface, iface_len + 1);
 }
 
 void add_addr(struct nft_rule *r, int offset,
@@ -251,15 +247,14 @@ void parse_meta(struct nft_rule_expr *e, uint8_t key, char *iniface,
 			*invflags |= IPT_INV_VIA_IN;
 
 		memcpy(iniface, ifname, len);
-		iniface[len] = '\0';
 
-		/* If zero, then this is an interface mask */
-		if (if_nametoindex(iniface) == 0) {
+		if (iniface[len] == '\0')
+			memset(iniface_mask, 0xff, len);
+		else {
 			iniface[len] = '+';
 			iniface[len+1] = '\0';
+			memset(iniface_mask, 0xff, len + 1);
 		}
-
-		memset(iniface_mask, 0xff, len);
 		break;
 	case NFT_META_OIFNAME:
 		ifname = nft_rule_expr_get(e, NFT_EXPR_CMP_DATA, &len);
@@ -267,15 +262,14 @@ void parse_meta(struct nft_rule_expr *e, uint8_t key, char *iniface,
 			*invflags |= IPT_INV_VIA_OUT;
 
 		memcpy(outiface, ifname, len);
-		outiface[len] = '\0';
 
-		/* If zero, then this is an interface mask */
-		if (if_nametoindex(outiface) == 0) {
+		if (outiface[len] == '\0')
+			memset(outiface_mask, 0xff, len);
+		else {
 			outiface[len] = '+';
 			outiface[len+1] = '\0';
+			memset(outiface_mask, 0xff, len + 1);
 		}
-
-		memset(outiface_mask, 0xff, len);
 		break;
 	default:
 		DEBUGP("unknown meta key %d\n", key);
-- 
1.7.10.4