src: add ability to set/get secmarks to/from connection

Labeling established and related packets requires the secmark to be stored in the connection.
Add the ability to store and retrieve secmarks like:

    ...
    chain input {
        ...

        # label new incoming packets
        ct state new meta secmark set tcp dport map @secmapping_in

        # add label to connection
        ct state new ct secmark set meta secmark

        # set label for est/rel packets from connection
        ct state established,related meta secmark set ct secmark

        ...
    }
    ...
    chain output {
        ...

        # label new outgoing packets
        ct state new meta secmark set tcp dport map @secmapping_out

        # add label to connection
        ct state new ct secmark set meta secmark

        # set label for est/rel packets from connection
        ct state established,related meta secmark set ct secmark

        ...
        }
    ...

This patch also disallow constant value on the right hand side.

    # nft add rule x y meta secmark 12
    Error: Cannot be used with right hand side constant value
    add rule x y meta secmark 12
                 ~~~~~~~~~~~~ ^^
    # nft add rule x y ct secmark 12
    Error: Cannot be used with right hand side constant value
    add rule x y ct secmark 12
                 ~~~~~~~~~~ ^^
    # nft add rule x y ct secmark set 12
    Error: ct secmark must not be set to constant value
    add rule x y ct secmark set 12
                 ^^^^^^^^^^^^^^^^^

This patch improves 3bc84e5c1fdd ("src: add support for setting secmark").

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 22 insertions, 2 deletions

diff --git a/src/evaluate.c b/src/evaluate.c
index e54eaf1a..a865902c 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -1784,6 +1784,18 @@ static int expr_evaluate_relational(struct eval_ctx *ctx, struct expr **expr)
 					 left->dtype->desc,
 					 right->dtype->desc);
 
+	/*
+	 * Statements like 'ct secmark 12' are parsed as relational,
+	 * disallow constant value on the right hand side.
+	 */
+	if (((left->etype == EXPR_META &&
+	      left->meta.key == NFT_META_SECMARK) ||
+	     (left->etype == EXPR_CT &&
+	      left->ct.key == NFT_CT_SECMARK)) &&
+	    right->flags & EXPR_F_CONSTANT)
+		return expr_binary_error(ctx->msgs, right, left,
+					 "Cannot be used with right hand side constant value");
+
 	switch (rel->op) {
 	case OP_EQ:
 	case OP_IMPLICIT:
@@ -2319,11 +2331,19 @@ static int stmt_evaluate_meta(struct eval_ctx *ctx, struct stmt *stmt)
 
 static int stmt_evaluate_ct(struct eval_ctx *ctx, struct stmt *stmt)
 {
-	return stmt_evaluate_arg(ctx, stmt,
+	if (stmt_evaluate_arg(ctx, stmt,
 				 stmt->ct.tmpl->dtype,
 				 stmt->ct.tmpl->len,
 				 stmt->ct.tmpl->byteorder,
-				 &stmt->ct.expr);
+				 &stmt->ct.expr) < 0)
+		return -1;
+
+	if (stmt->ct.key == NFT_CT_SECMARK &&
+	    expr_is_constant(stmt->ct.expr))
+		return stmt_error(ctx, stmt,
+				  "ct secmark must not be set to constant value");
+
+	return 0;
 }
 
 static int reject_payload_gen_dependency_tcp(struct eval_ctx *ctx,