evaluate: reject: support ethernet as L2 protocol for inet table

When we are evaluating a `reject` statement in the `inet` family, we may
have `ether` and `ip` or `ip6` as the L2 and L3 protocols in the
evaluation context:

  table inet filter {
    chain input {
      type filter hook input priority filter;
      ether saddr aa:bb:cc:dd:ee:ff ip daddr 192.168.0.1 reject
    }
  }

Since no `reject` option is given, nft attempts to infer one and fails:

  BUG: unsupported familynft: evaluate.c:2766:stmt_evaluate_reject_inet_family: Assertion `0' failed.
  Aborted

The reason it fails is that the ethernet protocol numbers for IPv4 and
IPv6 (`ETH_P_IP` and `ETH_P_IPV6`) do not match `NFPROTO_IPV4` and
`NFPROTO_IPV6`.  Add support for the ethernet protocol numbers.

Replace the current `BUG("unsupported family")` error message with
something more informative that tells the user to provide an explicit
reject option.

Add a Python test case.

Fixes: 5fdd0b6a0600 ("nft: complete reject support")
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1001360
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

4 files changed, 52 insertions, 1 deletions

diff --git a/src/evaluate.c b/src/evaluate.c
index 4d4dcc2e..8edefbd1 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -2751,19 +2751,22 @@ static int stmt_evaluate_reject_inet_family(struct eval_ctx *ctx,
 		protocol = proto_find_num(base, desc);
 		switch (protocol) {
 		case NFPROTO_IPV4:
+		case __constant_htons(ETH_P_IP):
 			if (stmt->reject.family == NFPROTO_IPV4)
 				break;
 			return stmt_binary_error(ctx, stmt->reject.expr,
 				  &ctx->pctx.protocol[PROTO_BASE_NETWORK_HDR],
 				  "conflicting protocols specified: ip vs ip6");
 		case NFPROTO_IPV6:
+		case __constant_htons(ETH_P_IPV6):
 			if (stmt->reject.family == NFPROTO_IPV6)
 				break;
 			return stmt_binary_error(ctx, stmt->reject.expr,
 				  &ctx->pctx.protocol[PROTO_BASE_NETWORK_HDR],
 				  "conflicting protocols specified: ip vs ip6");
 		default:
-			BUG("unsupported family");
+			return stmt_error(ctx, stmt,
+				  "cannot infer ICMP reject variant to use: explicit value required.\n");
 		}
 		break;
 	}
@@ -2923,10 +2926,12 @@ static int stmt_evaluate_reject_default(struct eval_ctx *ctx,
 		protocol = proto_find_num(base, desc);
 		switch (protocol) {
 		case NFPROTO_IPV4:
+		case __constant_htons(ETH_P_IP):
 			stmt->reject.family = NFPROTO_IPV4;
 			stmt->reject.icmp_code = ICMP_PORT_UNREACH;
 			break;
 		case NFPROTO_IPV6:
+		case __constant_htons(ETH_P_IPV6):
 			stmt->reject.family = NFPROTO_IPV6;
 			stmt->reject.icmp_code = ICMP6_DST_UNREACH_NOPORT;
 			break;
diff --git a/tests/py/inet/reject.t b/tests/py/inet/reject.t
index 1c8aeebe..61a6d556 100644
--- a/tests/py/inet/reject.t
+++ b/tests/py/inet/reject.t
@@ -37,3 +37,5 @@ meta l4proto udp reject with tcp reset;fail
 
 meta nfproto ipv4 reject with icmpx admin-prohibited;ok
 meta nfproto ipv6 reject with icmpx admin-prohibited;ok
+
+ether saddr aa:bb:cc:dd:ee:ff ip daddr 192.168.0.1 reject;ok;ether saddr aa:bb:cc:dd:ee:ff ip daddr 192.168.0.1 reject with icmp port-unreachable
diff --git a/tests/py/inet/reject.t.json b/tests/py/inet/reject.t.json
index 76cd1bf5..02ac9007 100644
--- a/tests/py/inet/reject.t.json
+++ b/tests/py/inet/reject.t.json
@@ -295,3 +295,37 @@
     }
 ]
 
+# ether saddr aa:bb:cc:dd:ee:ff ip daddr 192.168.0.1 reject
+[
+    {
+        "match": {
+            "left": {
+                "payload": {
+                    "field": "saddr",
+                    "protocol": "ether"
+                }
+            },
+            "op": "==",
+            "right": "aa:bb:cc:dd:ee:ff"
+        }
+    },
+    {
+        "match": {
+            "left": {
+                "payload": {
+                    "field": "daddr",
+                    "protocol": "ip"
+                }
+            },
+            "op": "==",
+            "right": "192.168.0.1"
+        }
+    },
+    {
+        "reject": {
+            "expr": "port-unreachable",
+            "type": "icmp"
+        }
+    }
+]
+
diff --git a/tests/py/inet/reject.t.payload.inet b/tests/py/inet/reject.t.payload.inet
index 62078d91..828cb839 100644
--- a/tests/py/inet/reject.t.payload.inet
+++ b/tests/py/inet/reject.t.payload.inet
@@ -132,3 +132,13 @@ inet test-inet input
   [ cmp eq reg 1 0x0000000a ]
   [ reject type 2 code 3 ]
 
+# ether saddr aa:bb:cc:dd:ee:ff ip daddr 192.168.0.1 reject
+inet test-inet input
+  [ meta load iiftype => reg 1 ]
+  [ cmp eq reg 1 0x00000001 ]
+  [ payload load 8b @ link header + 6 => reg 1 ]
+  [ cmp eq reg 1 0xddccbbaa 0x0008ffee ]
+  [ payload load 4b @ network header + 16 => reg 1 ]
+  [ cmp eq reg 1 0x0100a8c0 ]
+  [ reject type 0 code 3 ]
+