expr: reject: Do not print unset values in xml

It changes the parse and the snprint functions to omit unset values.

If we used this rule:
nft add rule ip test output reject

It gets this xml file:
[...]
<expr type="reject">
	<type>0</type>
	<code>0</code>
</expr>
</rule></nftables>

Now, That rule creates this xml file without null values:

[...]
<expr type="reject">
</expr>
</rule></nftables>

Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/src/expr/reject.c b/src/expr/reject.c
index 35aa9646e0a48e9cb7804168c83884927dbcce26..3a7604879aa2782aa6cc87c899f2894dda860fd1 100644 (file)
--- a/src/expr/reject.c
+++ b/src/expr/reject.c
@@ -155,14 +155,12 @@ nft_rule_expr_reject_xml_parse(struct nft_rule_expr *e, mxml_node_t *tree,
        uint8_t code;
 
        if (nft_mxml_num_parse(tree, "type", MXML_DESCEND_FIRST, BASE_DEC,
-                              &type, NFT_TYPE_U32, NFT_XML_MAND, err) < 0)
-               return -1;
-       nft_rule_expr_set_u32(e, NFT_EXPR_REJECT_TYPE, type);
+                              &type, NFT_TYPE_U32, NFT_XML_MAND, err) == 0)
+               nft_rule_expr_set_u32(e, NFT_EXPR_REJECT_TYPE, type);
 
        if (nft_mxml_num_parse(tree, "code", MXML_DESCEND_FIRST, BASE_DEC,
-                              &code, NFT_TYPE_U8, NFT_XML_MAND, err) < 0)
-               return -1;
-       nft_rule_expr_set_u8(e, NFT_EXPR_REJECT_CODE, code);
+                              &code, NFT_TYPE_U8, NFT_XML_MAND, err) == 0)
+               nft_rule_expr_set_u8(e, NFT_EXPR_REJECT_CODE, code);
 
        return 0;
 #else
@@ -183,11 +181,21 @@ static int nft_rule_expr_reject_snprintf_default(char *buf, size_t len,
 static int nft_rule_expr_reject_snprintf_xml(char *buf, size_t len,
                                             struct nft_rule_expr *e)
 {
+       int ret, size = len, offset = 0;
        struct nft_expr_reject *reject = nft_expr_data(e);
 
-       return snprintf(buf, len, "<type>%u</type>"
-                                 "<code>%u</code>",
-                       reject->type, reject->icmp_code);
+       if (e->flags & (1 << NFT_EXPR_REJECT_TYPE)) {
+               ret = snprintf(buf+offset, len, "<type>%u</type>",
+                              reject->type);
+               SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+       }
+       if (e->flags & (1 << NFT_EXPR_REJECT_CODE)) {
+               ret = snprintf(buf+offset, len, "<code>%u</code>",
+                              reject->icmp_code);
+               SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+       }
+
+       return offset;
 }
 
 static int nft_rule_expr_reject_snprintf_json(char *buf, size_t len,