expr: log: 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 log

We got this xml file:
<rule><family>ip</family>
<table>test</table>
<chain>output</chain>
<handle>88</handle>
<expr type="log">
        <prefix>(null)</prefix>
        <group>0</group>
        <snaplen>0</snaplen>
        <qthreshold>0</qthreshold>
</expr>
</rule>

And It was imposible import this file.

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

<rule><family>ip</family>
<table>test</table>
<chain>output</chain>
<handle>88</handle>
<expr type="log">
</expr>
</rule>

and It's possible import this xml file.

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

diff --git a/src/expr/log.c b/src/expr/log.c
index 497d5a3743904602a5694f1303ecb0638867b7d4..bd9bdc59ff54fa27faaa497e0138308f7dacb7d9 100644 (file)
--- a/src/expr/log.c
+++ b/src/expr/log.c
@@ -210,25 +210,21 @@ static int nft_rule_expr_log_xml_parse(struct nft_rule_expr *e,
 
        prefix = nft_mxml_str_parse(tree, "prefix", MXML_DESCEND_FIRST,
                                    NFT_XML_MAND, err);
-       if (prefix == NULL)
-               return -1;
-       nft_rule_expr_set_str(e, NFT_EXPR_LOG_PREFIX, prefix);
+       if (prefix != NULL)
+               nft_rule_expr_set_str(e, NFT_EXPR_LOG_PREFIX, prefix);
 
        if (nft_mxml_num_parse(tree, "group", MXML_DESCEND_FIRST, BASE_DEC,
-                              &group, NFT_TYPE_U16, NFT_XML_MAND, err) < 0)
-               return -1;
-       nft_rule_expr_set_u16(e, NFT_EXPR_LOG_GROUP, group);
+                              &group, NFT_TYPE_U16, NFT_XML_MAND, err) == 0)
+               nft_rule_expr_set_u16(e, NFT_EXPR_LOG_GROUP, group);
 
        if (nft_mxml_num_parse(tree, "snaplen", MXML_DESCEND_FIRST, BASE_DEC,
-                              &snaplen, NFT_TYPE_U32, NFT_XML_MAND, err) < 0)
-               return -1;
-       nft_rule_expr_set_u32(e, NFT_EXPR_LOG_SNAPLEN, snaplen);
+                              &snaplen, NFT_TYPE_U32, NFT_XML_MAND, err) == 0)
+               nft_rule_expr_set_u32(e, NFT_EXPR_LOG_SNAPLEN, snaplen);
 
        if (nft_mxml_num_parse(tree, "qthreshold", MXML_DESCEND_FIRST, BASE_DEC,
                               &qthreshold, NFT_TYPE_U16, NFT_XML_MAND,
-                              err) < 0)
-               return -1;
-       nft_rule_expr_set_u16(e, NFT_EXPR_LOG_QTHRESHOLD, qthreshold);
+                              err) == 0)
+               nft_rule_expr_set_u16(e, NFT_EXPR_LOG_QTHRESHOLD, qthreshold);
 
        return 0;
 #else
@@ -250,14 +246,31 @@ static int nft_rule_expr_log_snprintf_default(char *buf, size_t len,
 static int nft_rule_expr_log_snprintf_xml(char *buf, size_t size,
                                          struct nft_rule_expr *e)
 {
+       int ret, len = size, offset = 0;
        struct nft_expr_log *log = nft_expr_data(e);
 
-       return snprintf(buf, size, "<prefix>%s</prefix>"
-                                  "<group>%u</group>"
-                                  "<snaplen>%u</snaplen>"
-                                  "<qthreshold>%u</qthreshold>",
-                       log->prefix, log->group,
-                       log->snaplen, log->qthreshold);
+       if (e->flags & (1 << NFT_EXPR_LOG_PREFIX)) {
+               ret = snprintf(buf + offset, len, "<prefix>%s</prefix>",
+                              log->prefix);
+               SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+       }
+       if (e->flags & (1 << NFT_EXPR_LOG_GROUP)) {
+               ret = snprintf(buf + offset, len, "<group>%u</group>",
+                              log->group);
+               SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+       }
+       if (e->flags & (1 << NFT_EXPR_LOG_SNAPLEN)) {
+               ret = snprintf(buf + offset, len, "<snaplen>%u</snaplen>",
+                              log->snaplen);
+               SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+       }
+       if (e->flags & (1 << NFT_EXPR_LOG_QTHRESHOLD)) {
+               ret = snprintf(buf + offset, len, "<qthreshold>%u</qthreshold>",
+                              log->qthreshold);
+               SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+       }
+
+       return offset;
 }
 
 static int nft_rule_expr_log_snprintf_json(char *buf, size_t len,