evaluate: wrap protocol context debunk into function

ether type vlan sets the network layer protocol context to vlan. This
function debunks the existing link layer protocol context by setting it
to vlan.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 19 insertions, 6 deletions

diff --git a/src/evaluate.c b/src/evaluate.c
index b70ff07c..e53627a5 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -382,6 +382,17 @@ static int meta_iiftype_gen_dependency(struct eval_ctx *ctx,
 	return 0;
 }
 
+static void proto_ctx_debunk(struct eval_ctx *ctx,
+			     const struct proto_desc *desc,
+			     const struct proto_desc *next,
+			     struct expr *payload, enum proto_bases base)
+{
+	ctx->pctx.protocol[base + 1].desc = NULL;
+	ctx->pctx.protocol[base].desc = next;
+	ctx->pctx.protocol[base].offset += desc->length;
+	payload->payload.offset += desc->length;
+}
+
 static bool proto_is_dummy(const struct proto_desc *desc)
 {
 	return desc == &proto_inet || desc == &proto_netdev;
@@ -406,16 +417,18 @@ static int resolve_protocol_conflict(struct eval_ctx *ctx,
 	assert(base < PROTO_BASE_MAX);
 	next = ctx->pctx.protocol[base + 1].desc;
 
+	/* ether type vlan sets vlan as network protocol, debunk ethernet if it
+	 * is already there.
+	 */
 	if (payload->payload.desc == next) {
-		ctx->pctx.protocol[base + 1].desc = NULL;
-		ctx->pctx.protocol[base].desc = next;
-		ctx->pctx.protocol[base].offset += desc->length;
-		payload->payload.offset += desc->length;
+		proto_ctx_debunk(ctx, desc, next, payload, base);
 		return 0;
-	} else if (next) {
-		return 1;
 	}
 
+	/* This payload and the existing context don't match, conflict. */
+	if (next != NULL)
+		return 1;
+
 	link = proto_find_num(desc, payload->payload.desc);
 	if (link < 0 || conflict_resolution_gen_dependency(ctx, link, payload, &nstmt) < 0)
 		return 1;