[PATCH 1/4 v3] libnftnl: Implement new buffer of TLV objects.

["Carlos Falgueras García" <carlosfg@riseup.net>]

These functions allow to create a buffer (nftnl_udata_buf) of TLV objects
(nftnl_udata). It is inspired by libmnl/src/attr.c. It can be used to store
several variable length user data into an object.

Example usage:
	```
	struct nftnl_udata_buf *buf;
	struct nftnl_udata *attr;
	const char str[] = "Hello World!";

	buf = nftnl_udata_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_free(buf);
	```

Signed-off-by: Carlos Falgueras García <carlosfg@riseup.net>
---
 include/Makefile.am          |   1 +
 include/libnftnl/Makefile.am |   1 +
 include/libnftnl/udata.h     |  53 +++++++++++++++++
 include/udata.h              |  40 +++++++++++++
 src/Makefile.am              |   1 +
 src/libnftnl.map             |  16 ++++++
 src/udata.c                  | 132 +++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 244 insertions(+)
 create mode 100644 include/libnftnl/udata.h
 create mode 100644 include/udata.h
 create mode 100644 src/udata.c

diff --git a/include/Makefile.am b/include/Makefile.am
index be9eb9b..9f55737 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -12,4 +12,5 @@ noinst_HEADERS = internal.h	\
 		 expr.h		\
 		 json.h		\
 		 set_elem.h	\
+		 udata.h	\
 		 utils.h
diff --git a/include/libnftnl/Makefile.am b/include/libnftnl/Makefile.am
index 84f01b6..457ec95 100644
--- a/include/libnftnl/Makefile.am
+++ b/include/libnftnl/Makefile.am
@@ -7,4 +7,5 @@ pkginclude_HEADERS = batch.h		\
 		     set.h		\
 		     ruleset.h		\
 		     common.h		\
+		     udata.h		\
 		     gen.h
diff --git a/include/libnftnl/udata.h b/include/libnftnl/udata.h
new file mode 100644
index 0000000..cf328b4
--- /dev/null
+++ b/include/libnftnl/udata.h
@@ -0,0 +1,53 @@
+#ifndef _LIBNFTNL_UDATA_H_
+#define _LIBNFTNL_UDATA_H_
+
+#include <stdio.h>
+#include <stdint.h>
+
+/*
+ * nftnl user data attributes API
+ */
+struct nftnl_udata;
+struct nftnl_udata_buf;
+
+/* nftnl_udata_buf */
+struct nftnl_udata_buf *nftnl_udata_alloc(size_t data_size);
+void nftnl_udata_free(struct nftnl_udata_buf *buf);
+size_t nftnl_udata_len(const struct nftnl_udata_buf *buf);
+size_t nftnl_udata_size(const struct nftnl_udata_buf *buf);
+void *nftnl_udata_data(const struct nftnl_udata_buf *buf);
+void nftnl_udata_copy_data(struct nftnl_udata_buf *buf, const void *data,
+			   size_t len);
+struct nftnl_udata *nftnl_udata_start(const struct nftnl_udata_buf *buf);
+struct nftnl_udata *nftnl_udata_end(const struct nftnl_udata_buf *buf);
+
+/* putters */
+struct nftnl_udata *nftnl_udata_put(struct nftnl_udata_buf *buf, uint8_t type,
+				    size_t len, const void *value);
+struct nftnl_udata *nftnl_udata_put_strz(struct nftnl_udata_buf *buf,
+					 uint8_t type, const char *strz);
+
+/* nftnl_udata_attr */
+uint8_t nftnl_udata_attr_type(const struct nftnl_udata *attr);
+uint8_t nftnl_udata_attr_len(const struct nftnl_udata *attr);
+void *nftnl_udata_attr_value(const struct nftnl_udata *attr);
+
+/* iterator */
+struct nftnl_udata *nftnl_udata_attr_next(const struct nftnl_udata *attr);
+
+#define nftnl_udata_for_each(buf, attr)                       \
+	for ((attr) = nftnl_udata_start(buf);                 \
+	     (char *)(nftnl_udata_end(buf)) > (char *)(attr); \
+	     (attr) = nftnl_udata_attr_next(attr))
+
+/* callback-based attribute parsers */
+#define NFTNL_CB_ERROR	-1
+#define NFTNL_CB_STOP	 0
+#define NFTNL_CB_OK	 1
+
+typedef int (*nftnl_udata_cb_t)(const struct nftnl_udata *attr,
+				void *data);
+int nftnl_udata_parse(const struct nftnl_udata_buf *buf, nftnl_udata_cb_t cb,
+		      void *data);
+
+#endif /* _LIBNFTNL_UDATA_H_ */
diff --git a/include/udata.h b/include/udata.h
new file mode 100644
index 0000000..271ee50
--- /dev/null
+++ b/include/udata.h
@@ -0,0 +1,40 @@
+#ifndef _LIBNFTNL_UDATA_INTERNAL_H_
+#define _LIBNFTNL_UDATA_INTERNAL_H_
+
+#include <stdint.h>
+#include <stddef.h>
+
+/*
+ * TLV structures:
+ * nftnl_udata
+ *  <-------- HEADER --------> <------ PAYLOAD ------>
+ * +------------+-------------+- - - - - - - - - - - -+
+ * |    type    |     len     |         value         |
+ * |  (1 byte)  |   (1 byte)  |                       |
+ * +--------------------------+- - - - - - - - - - - -+
+ *  <-- sizeof(nftnl_udata) -> <-- nftnl_udata->len -->
+ */
+struct nftnl_udata {
+	uint8_t type;
+	uint8_t len;
+	unsigned char value[];
+} __attribute__((__packed__));
+
+/*
+ *              +---------------------------------++
+ *              | data[]                          ||
+ *              |   ||                            ||
+ *              |   \/                            \/
+ *  +-------+-------+-------+-------+ ... +-------+- - - - - - -+
+ *  | size  |  end  |  TLV  |  TLV  |     |  TLV  |    Empty    |
+ *  +-------+-------+-------+-------+ ... +-------+- - - - - - -+
+ *                  |<---- nftnl_udata_len() ---->|
+ *                  |<----------- nftnl_udata_size() ---------->|
+ */
+struct nftnl_udata_buf {
+	size_t size;
+	char  *end;
+	char   data[];
+};
+
+#endif /* _LIBNFTNL_UDATA_INTERNAL_H_ */
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..d6cd2a7 100644
--- a/src/libnftnl.map
+++ b/src/libnftnl.map
@@ -336,6 +336,22 @@ global:
   nftnl_set_snprintf;
   nftnl_set_fprintf;
 
+  nftnl_udata_alloc;
+  nftnl_udata_free;
+  nftnl_udata_len;
+  nftnl_udata_size;
+  nftnl_udata_data;
+  nftnl_udata_copy_data;
+  nftnl_udata_start;
+  nftnl_udata_end;
+  nftnl_udata_put;
+  nftnl_udata_put_strz;
+  nftnl_udata_attr_type;
+  nftnl_udata_attr_len;
+  nftnl_udata_attr_value;
+  nftnl_udata_attr_next;
+  nftnl_udata_parse;
+
   nftnl_set_list_alloc;
   nftnl_set_list_free;
   nftnl_set_list_add;
diff --git a/src/udata.c b/src/udata.c
new file mode 100644
index 0000000..71a2c46
--- /dev/null
+++ b/src/udata.c
@@ -0,0 +1,132 @@
+#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_alloc(size_t data_size)
+{
+	struct nftnl_udata_buf *buf;
+
+	buf = (struct nftnl_udata_buf *)
+		malloc(sizeof(struct nftnl_udata_buf) + data_size);
+	buf->size = data_size;
+	buf->end = buf->data;
+
+	return buf;
+}
+EXPORT_SYMBOL(nftnl_udata_alloc);
+
+void nftnl_udata_free(struct nftnl_udata_buf *buf)
+{
+	buf->size = 0;
+	buf->end = NULL;
+	free((void *)buf);
+}
+EXPORT_SYMBOL(nftnl_udata_free);
+
+size_t nftnl_udata_len(const struct nftnl_udata_buf *buf)
+{
+	return (size_t)(buf->end - buf->data);
+}
+EXPORT_SYMBOL(nftnl_udata_len);
+
+size_t nftnl_udata_size(const struct nftnl_udata_buf *buf)
+{
+	return buf->size;
+}
+EXPORT_SYMBOL(nftnl_udata_size);
+
+void *nftnl_udata_data(const struct nftnl_udata_buf *buf)
+{
+	return (void *)buf->data;
+}
+EXPORT_SYMBOL(nftnl_udata_data);
+
+void nftnl_udata_copy_data(struct nftnl_udata_buf *buf,
+			   const void *data, size_t len)
+{
+	memcpy(buf->data, data, len <= buf->size ? len : buf->size);
+	buf->end = buf->data + len;
+}
+EXPORT_SYMBOL(nftnl_udata_copy_data);
+
+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);
+
+struct nftnl_udata *nftnl_udata_put(struct nftnl_udata_buf *buf,
+				    uint8_t type, size_t len, const void *value)
+{
+	struct nftnl_udata *attr = NULL;
+
+	/* Check if there is enough space */
+	if (buf->size >= len + sizeof(struct nftnl_udata)) {
+		attr = (struct nftnl_udata *)buf->end;
+		attr->len  = len;
+		attr->type = type;
+		memcpy(attr->value, value, len);
+
+		buf->end = (char *)nftnl_udata_attr_next(attr);
+	}
+
+	return attr;
+}
+EXPORT_SYMBOL(nftnl_udata_put);
+
+struct nftnl_udata *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_attr_type(const struct nftnl_udata *attr)
+{
+	return attr->type;
+}
+EXPORT_SYMBOL(nftnl_udata_attr_type);
+
+uint8_t nftnl_udata_attr_len(const struct nftnl_udata *attr)
+{
+	return attr->len;
+}
+EXPORT_SYMBOL(nftnl_udata_attr_len);
+
+void *nftnl_udata_attr_value(const struct nftnl_udata *attr)
+{
+	return (void *)attr->value;
+}
+EXPORT_SYMBOL(nftnl_udata_attr_value);
+
+struct nftnl_udata *nftnl_udata_attr_next(const struct nftnl_udata *attr)
+{
+	return (struct nftnl_udata *)&attr->value[attr->len];
+}
+EXPORT_SYMBOL(nftnl_udata_attr_next);
+
+int nftnl_udata_parse(const struct nftnl_udata_buf *buf, nftnl_udata_cb_t cb,
+		     void *data)
+{
+	int ret = NFTNL_CB_OK;
+	const struct nftnl_udata *attr;
+
+	nftnl_udata_for_each(buf, attr) {
+		ret = cb(attr, data);
+		if (ret <= NFTNL_CB_STOP)
+			return ret;
+	}
+	return ret;
+}
+EXPORT_SYMBOL(nftnl_udata_parse);
-- 
2.7.2

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