[lnf-log,PATCHv2,3/3] nlmsg: add printf function in conjunction with libmnl

diff --git a/include/internal.h b/include/internal.h
new file mode 100644
index 0000000..7839fd8
--- /dev/null
+++ b/include/internal.h
@@ -0,0 +1,9 @@ 
+#ifndef _LIBNETFILTER_LOG_INTERNAL_H
+#define _LIBNETFILTER_LOG_INTERNAL_H
+
+struct nflog_data
+{
+	struct nfattr **nfa;
+};
+
+#endif
diff --git a/include/libnetfilter_log/libnetfilter_log.h b/include/libnetfilter_log/libnetfilter_log.h
index 5087f6f..46767eb 100644
--- a/include/libnetfilter_log/libnetfilter_log.h
+++ b/include/libnetfilter_log/libnetfilter_log.h
@@ -89,4 +89,12 @@  extern int nflog_attr_put_cfg_mode(struct nlmsghdr *nlh, uint8_t mode, uint32_t
 extern int nflog_attr_put_cfg_cmd(struct nlmsghdr *nlh, uint8_t cmd);
 extern int nflog_nlmsg_parse(const struct nlmsghdr *nlh, struct nlattr **attr);
 
+enum nflog_output_type {
+	NFLOG_OUTPUT_XML	= 0,
+};
+
+int nflog_nlmsg_snprintf(char *buf, size_t bufsiz, const struct nlmsghdr *nlh,
+			 struct nlattr **attr, enum nflog_output_type type,
+			 uint32_t flags);
+
 #endif	/* __LIBNETFILTER_LOG_H */
diff --git a/src/libnetfilter_log.c b/src/libnetfilter_log.c
index e92576b..567049c 100644
--- a/src/libnetfilter_log.c
+++ b/src/libnetfilter_log.c
@@ -26,6 +26,7 @@ 
 #include <errno.h>
 #include <netinet/in.h>
 #include <sys/socket.h>
+#include "internal.h"
 
 #include <libnetfilter_log/linux_nfnetlink_log.h>
 
@@ -78,11 +79,6 @@  struct nflog_g_handle
 	void *data;
 };
 
-struct nflog_data
-{
-	struct nfattr **nfa;
-};
-
 int nflog_errno;
 
 /***********************************************************************
diff --git a/src/nlmsg.c b/src/nlmsg.c
index a917a70..708e32d 100644
--- a/src/nlmsg.c
+++ b/src/nlmsg.c
@@ -9,6 +9,9 @@ 
 #include <arpa/inet.h>
 #include <linux/netfilter/nfnetlink_log.h>
 #include <libmnl/libmnl.h>
+#include <libnetfilter_log/libnetfilter_log.h>
+#include <errno.h>
+#include "internal.h"
 
 /**
  * \defgroup nlmsg Netlink message helper functions
@@ -157,5 +160,55 @@  int nflog_nlmsg_parse(const struct nlmsghdr *nlh, struct nlattr **attr)
 }
 
 /**
+ * nflog_nlmsg_snprintf - print a nflog nlattrs to a buffer
+ * \param buf buffer used to build the printable nflog
+ * \param bufsiz size of the buffer
+ * \param nlh netlink message (to get queue num in the futuer)
+ * \param attr pointer to a nflog attrs
+ * \param type print message type in enum nflog_output_type
+ * \param flags The flag that tell what to print into the buffer
+ *
+ * This function supports the following type - flags:
+ *
+ *   type: NFLOG_OUTPUT_XML
+ *	- NFLOG_XML_PREFIX: include the string prefix
+ *	- NFLOG_XML_HW: include the hardware link layer address
+ *	- NFLOG_XML_MARK: include the packet mark
+ *	- NFLOG_XML_DEV: include the device information
+ *	- NFLOG_XML_PHYSDEV: include the physical device information
+ *	- NFLOG_XML_PAYLOAD: include the payload (in hexadecimal)
+ *	- NFLOG_XML_TIME: include the timestamp
+ *	- NFLOG_XML_ALL: include all the logging information (all flags set)
+ *
+ * You can combine this flags with an binary OR.
+ *
+ * this function returns -1 and errno is explicitly set in case of
+ * failure, otherwise the length of the string that would have been
+ * printed into the buffer (in case that there is enough room in
+ * it). See snprintf() return value for more information.
+ */
+int nflog_nlmsg_snprintf(char *buf, size_t bufsiz, const struct nlmsghdr *nlh,
+			 struct nlattr **attr, enum nflog_output_type type,
+			 uint32_t flags)
+{
+	/* This is a hack to re-use the existing old API code. */
+	struct nflog_data nfad = {
+		.nfa	= (struct nfattr **)&attr[1],
+	};
+	int ret;
+
+	switch (type) {
+	case NFLOG_OUTPUT_XML:
+		ret = nflog_snprintf_xml(buf, bufsiz, &nfad, flags);
+		break;
+	default:
+		ret = -1;
+		errno = EOPNOTSUPP;
+		break;
+	}
+	return ret;
+}
+
+/**
  * @}
  */
diff --git a/utils/nf-log.c b/utils/nf-log.c
index d575b77..5f2a192 100644
--- a/utils/nf-log.c
+++ b/utils/nf-log.c
@@ -14,6 +14,7 @@  static int log_cb(const struct nlmsghdr *nlh, void *data)
 	struct nfulnl_msg_packet_hdr *ph = NULL;
 	const char *prefix = NULL;
 	uint32_t mark = 0;
+	char buf[4096];
 	int ret;
 
 	ret = nflog_nlmsg_parse(nlh, attrs);
@@ -31,6 +32,12 @@  static int log_cb(const struct nlmsghdr *nlh, void *data)
 		prefix ? prefix : "", ntohs(ph->hw_protocol), ph->hook,
 		mark);
 
+	ret = nflog_nlmsg_snprintf(buf, sizeof(buf), nlh, attrs,
+				   NFLOG_OUTPUT_XML, NFLOG_XML_ALL);
+	if (ret < 0)
+		return MNL_CB_ERROR;
+	printf("%s (ret=%d)\n", buf, ret);
+
 	return MNL_CB_OK;
 }