udata: add TLV user data infrastructure

These functions allow to create a buffer (struct nftnl_udata_buf) of
user data attributes in TLV format (struct nftnl_udata). It is inspired
by libmnl/src/attr.c. It can be used to store several TLVs sequentially
into an object.

Example:

	struct nftnl_udata_buf *buf;
	struct nftnl_udata *attr;
	const char *str = "Hello World!";

	buf = nftnl_udata_buf_alloc(UDATA_SIZE);
	if (!buf) {
		perror("OOM");
		exit(EXIT_FAILURE);
	}

	if (!nftnl_udata_put_strz(buf, MY_TYPE, str)) {
		perror("Can't put attribute \"%s\"", str);
		exit(EXIT_FAILURE);
	}

	nftnl_udata_for_each(buf, attr)
		printf("%s\n", (char *)nftnl_udata_attr_value(attr));

	nftnl_udata_buf_free(buf);

Signed-off-by: Carlos Falgueras García <carlosfg@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 151 insertions, 0 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index a27e292..7e580e4 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -19,6 +19,7 @@ libnftnl_la_SOURCES = utils.c		\
 		      ruleset.c		\
 		      mxml.c		\
 		      jansson.c		\
+		      udata.c		\
 		      expr.c		\
 		      expr_ops.c	\
 		      expr/bitwise.c	\
diff --git a/src/libnftnl.map b/src/libnftnl.map
index 2e193b7..c38e081 100644
--- a/src/libnftnl.map
+++ b/src/libnftnl.map
@@ -512,4 +512,19 @@ LIBNFTNL_4.1 {
 	nftnl_trace_get_data;
 
 	nftnl_trace_nlmsg_parse;
+
+	nftnl_udata_buf_alloc;
+	nftnl_udata_buf_free;
+	nftnl_udata_buf_len;
+	nftnl_udata_buf_data;
+	nftnl_udata_buf_put;
+	nftnl_udata_start;
+	nftnl_udata_end;
+	nftnl_udata_put;
+	nftnl_udata_put_strz;
+	nftnl_udata_type;
+	nftnl_udata_len;
+	nftnl_udata_get;
+	nftnl_udata_next;
+	nftnl_udata_parse;
 } LIBNFTNL_4;
diff --git a/src/udata.c b/src/udata.c
new file mode 100644
index 0000000..03aac63
--- /dev/null
+++ b/src/udata.c
@@ -0,0 +1,135 @@
+/*
+ * (C) 2012-2016 by Pablo Neira Ayuso <pablo@netfilter.org>
+ * (C) 2016 by Carlos Falgueras García <carlosfg@riseup.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <libnftnl/udata.h>
+#include <udata.h>
+#include <utils.h>
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+struct nftnl_udata_buf *nftnl_udata_buf_alloc(uint32_t data_size)
+{
+	struct nftnl_udata_buf *buf;
+
+	buf = malloc(sizeof(struct nftnl_udata_buf) + data_size);
+	if (!buf)
+		return NULL;
+	buf->size = data_size;
+	buf->end = buf->data;
+
+	return buf;
+}
+EXPORT_SYMBOL(nftnl_udata_buf_alloc);
+
+void nftnl_udata_buf_free(struct nftnl_udata_buf *buf)
+{
+	free(buf);
+}
+EXPORT_SYMBOL(nftnl_udata_buf_free);
+
+uint32_t nftnl_udata_buf_len(const struct nftnl_udata_buf *buf)
+{
+	return (uint32_t)(buf->end - buf->data);
+}
+EXPORT_SYMBOL(nftnl_udata_buf_len);
+
+void *nftnl_udata_buf_data(const struct nftnl_udata_buf *buf)
+{
+	return (void *)buf->data;
+}
+EXPORT_SYMBOL(nftnl_udata_buf_data);
+
+void nftnl_udata_buf_put(struct nftnl_udata_buf *buf, const void *data,
+			 uint32_t len)
+{
+	memcpy(buf->data, data, len <= buf->size ? len : buf->size);
+	buf->end = buf->data + len;
+}
+EXPORT_SYMBOL(nftnl_udata_buf_put);
+
+struct nftnl_udata *nftnl_udata_start(const struct nftnl_udata_buf *buf)
+{
+	return (struct nftnl_udata *)buf->data;
+}
+EXPORT_SYMBOL(nftnl_udata_start);
+
+struct nftnl_udata *nftnl_udata_end(const struct nftnl_udata_buf *buf)
+{
+	return (struct nftnl_udata *)buf->end;
+}
+EXPORT_SYMBOL(nftnl_udata_end);
+
+bool nftnl_udata_put(struct nftnl_udata_buf *buf, uint8_t type, uint32_t len,
+		     const void *value)
+{
+	struct nftnl_udata *attr;
+
+	if (buf->size < len + sizeof(struct nftnl_udata))
+		return false;
+
+	attr = (struct nftnl_udata *)buf->end;
+	attr->len  = len;
+	attr->type = type;
+	memcpy(attr->value, value, len);
+
+	buf->end = (char *)nftnl_udata_next(attr);
+
+	return true;
+}
+EXPORT_SYMBOL(nftnl_udata_put);
+
+bool nftnl_udata_put_strz(struct nftnl_udata_buf *buf, uint8_t type,
+			  const char *strz)
+{
+	return nftnl_udata_put(buf, type, strlen(strz) + 1, strz);
+}
+EXPORT_SYMBOL(nftnl_udata_put_strz);
+
+uint8_t nftnl_udata_type(const struct nftnl_udata *attr)
+{
+	return attr->type;
+}
+EXPORT_SYMBOL(nftnl_udata_type);
+
+uint8_t nftnl_udata_len(const struct nftnl_udata *attr)
+{
+	return attr->len;
+}
+EXPORT_SYMBOL(nftnl_udata_len);
+
+void *nftnl_udata_get(const struct nftnl_udata *attr)
+{
+	return (void *)attr->value;
+}
+EXPORT_SYMBOL(nftnl_udata_get);
+
+struct nftnl_udata *nftnl_udata_next(const struct nftnl_udata *attr)
+{
+	return (struct nftnl_udata *)&attr->value[attr->len];
+}
+EXPORT_SYMBOL(nftnl_udata_next);
+
+int nftnl_udata_parse(const void *data, uint32_t data_len, nftnl_udata_cb_t cb,
+		      void *cb_data)
+{
+	int ret = 0;
+	const struct nftnl_udata *attr;
+
+	nftnl_udata_for_each_data(data, data_len, attr) {
+		ret = cb(attr, cb_data);
+		if (ret < 0)
+			return ret;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(nftnl_udata_parse);