diff mbox

[libnftnl,1/2] src: add flag to add event wrapping in output functions

Message ID 20140415125030.2590.5501.stgit@nfdev.cica.es
State Superseded
Headers show

Commit Message

Arturo Borrero April 15, 2014, 12:50 p.m. UTC 
This patch uses the flag option of each output function to print an
event wrapper string in each object.

In order to use this functionality, the caller must pass a flag with either
NFT_OUTPUT_FLAG_EVENTNEW or NFT_OUTPUT_FLAG_EVENTDEL activated.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
---
 include/libnftnl/common.h |    5 +++
 src/chain.c               |   37 ++++++++++++++++++++++---
 src/internal.h            |    2 +
 src/rule.c                |   43 ++++++++++++++++++++++++++---
 src/ruleset.c             |   66 ++++++++++++++++++++++++++++++++++++++++-----
 src/set.c                 |   42 +++++++++++++++++++++++++----
 src/set_elem.c            |   37 ++++++++++++++++++++++---
 src/table.c               |   36 +++++++++++++++++++++----
 src/utils.c               |   45 +++++++++++++++++++++++++++++++
 9 files changed, 280 insertions(+), 33 deletions(-)


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Comments

Pablo Neira Ayuso April 15, 2014, 1:36 p.m. UTC | #1 
On Tue, Apr 15, 2014 at 02:50:30PM +0200, Arturo Borrero Gonzalez wrote:
> This patch uses the flag option of each output function to print an
> event wrapper string in each object.
> 
> In order to use this functionality, the caller must pass a flag with either
> NFT_OUTPUT_FLAG_EVENTNEW or NFT_OUTPUT_FLAG_EVENTDEL activated.
> 
> Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
> ---
>  include/libnftnl/common.h |    5 +++
>  src/chain.c               |   37 ++++++++++++++++++++++---
>  src/internal.h            |    2 +
>  src/rule.c                |   43 ++++++++++++++++++++++++++---
>  src/ruleset.c             |   66 ++++++++++++++++++++++++++++++++++++++++-----
>  src/set.c                 |   42 +++++++++++++++++++++++++----
>  src/set_elem.c            |   37 ++++++++++++++++++++++---
>  src/table.c               |   36 +++++++++++++++++++++----
>  src/utils.c               |   45 +++++++++++++++++++++++++++++++
>  9 files changed, 280 insertions(+), 33 deletions(-)
> 
> diff --git a/include/libnftnl/common.h b/include/libnftnl/common.h
> index f0c20f0..f105c9a 100644
> --- a/include/libnftnl/common.h
> +++ b/include/libnftnl/common.h
> @@ -15,6 +15,11 @@ enum nft_output_type {
>  	NFT_OUTPUT_JSON,
>  };
>  
> +enum {
> +	NFT_OUTPUT_FLAG_EVENTNEW	= 0,
> +	NFT_OUTPUT_FLAG_EVENTDEL,
> +};

Please, change this to:

enum nft_output_flags {
        NFT_OF_EVENT_NEW        = (1 << 0),
        NFT_OF_EVENT_DEL        = (1 << 1),
};

So people don't need to use (1 << NFT_OUTPUT_FLAG_EVENTNEW) to pass
the flag to nft_*_snprintf from their applications.

> +
>  enum nft_parse_type {
>  	NFT_PARSE_NONE		= 0,
>  	NFT_PARSE_XML,
> diff --git a/src/chain.c b/src/chain.c
> index 472203e..87558a1 100644
> --- a/src/chain.c
> +++ b/src/chain.c
> @@ -924,17 +924,44 @@ static int nft_chain_snprintf_default(char *buf, size_t size,
>  int nft_chain_snprintf(char *buf, size_t size, struct nft_chain *c,
>  		       uint32_t type, uint32_t flags)
>  {
> +	int ret, len = size, offset = 0;
> +
> +	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
> +		ret = snprintf(buf+offset, len, "%s",

Use this instead "%9s ".

So you can use [NEW] and [DELETE] tags and the plain text event output
gets aligned (and you don't need to trim DELETE to DEL anymore).
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Pablo Neira Ayuso April 15, 2014, 1:44 p.m. UTC | #2 
On Tue, Apr 15, 2014 at 02:50:30PM +0200, Arturo Borrero Gonzalez wrote:
> diff --git a/src/chain.c b/src/chain.c
> index 472203e..87558a1 100644
> --- a/src/chain.c
> +++ b/src/chain.c
> @@ -924,17 +924,44 @@ static int nft_chain_snprintf_default(char *buf, size_t size,
>  int nft_chain_snprintf(char *buf, size_t size, struct nft_chain *c,
>  		       uint32_t type, uint32_t flags)
>  {
> +	int ret, len = size, offset = 0;
> +
> +	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
> +		ret = snprintf(buf+offset, len, "%s",
> +			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
> +						 type));
> +		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
> +	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
> +		ret = snprintf(buf+offset, len, "%s",
> +			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
> +						 type));
> +		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
> +	}
> +
[...]
> +	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
> +		ret = snprintf(buf+offset, len, "%s",
> +			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
> +						 type));
> +		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
> +		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTNEW);
> +	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
> +		ret = snprintf(buf+offset, len, "%s",
> +			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
> +						 type));
> +		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
> +		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTDEL);
> +	}

This code looks very similar, you can encapsulate it in one function
to add the heading and the trailer.

Regarding the noevent_flags thing, which is the only different, you can do:

        unsigned int inner_flags &= ~NFT_OF_EVENT_ANY;

And use inner_flags to when you have nested calls (ie. like in ruleset.c).

The NFT_OF_EVENT_ANY mask should be something like:

enum ... {
        NFT_OF_EVENT_ANY        = (NFT_OF_EVENT_NEW | NFT_OF_EVENT_DEL)
};

Thanks.
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diff mbox

Patch

diff --git a/include/libnftnl/common.h b/include/libnftnl/common.h
index f0c20f0..f105c9a 100644
--- a/include/libnftnl/common.h
+++ b/include/libnftnl/common.h
@@ -15,6 +15,11 @@  enum nft_output_type {
 	NFT_OUTPUT_JSON,
 };
 
+enum {
+	NFT_OUTPUT_FLAG_EVENTNEW	= 0,
+	NFT_OUTPUT_FLAG_EVENTDEL,
+};
+
 enum nft_parse_type {
 	NFT_PARSE_NONE		= 0,
 	NFT_PARSE_XML,
diff --git a/src/chain.c b/src/chain.c
index 472203e..87558a1 100644
--- a/src/chain.c
+++ b/src/chain.c
@@ -924,17 +924,44 @@  static int nft_chain_snprintf_default(char *buf, size_t size,
 int nft_chain_snprintf(char *buf, size_t size, struct nft_chain *c,
 		       uint32_t type, uint32_t flags)
 {
+	int ret, len = size, offset = 0;
+
+	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
 	switch(type) {
 	case NFT_OUTPUT_DEFAULT:
-		return nft_chain_snprintf_default(buf, size, c);
+		ret = nft_chain_snprintf_default(buf+offset, len, c);
+		break;
 	case NFT_OUTPUT_XML:
-		return nft_chain_snprintf_xml(buf, size, c);
+		ret = nft_chain_snprintf_xml(buf+offset, len, c);
+		break;
 	case NFT_OUTPUT_JSON:
-		return nft_chain_snprintf_json(buf, size, c);
-	default:
+		ret = nft_chain_snprintf_json(buf+offset, len, c);
 		break;
+	default:
+		return -1;
 	}
-	return -1;
+
+	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+
+	if ((flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) ||
+	    (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL))) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_closetag(type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
+	return offset;
 }
 EXPORT_SYMBOL(nft_chain_snprintf);
 
diff --git a/src/internal.h b/src/internal.h
index ba994c8..8979bb7 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -136,6 +136,8 @@  int nft_get_value(enum nft_type type, void *val, void *out);
 
 #include <stdio.h>
 int nft_fprintf(FILE *fp, void *obj, uint32_t type, uint32_t flags, int (*snprintf_cb)(char *buf, size_t bufsiz, void *obj, uint32_t type, uint32_t flags));
+const char *nft_event_opentag(uint32_t event, uint32_t format);
+const char *nft_event_closetag(uint32_t format);
 
 void xfree(const void *ptr);
 
diff --git a/src/rule.c b/src/rule.c
index df9dd80..0a9ee1d 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -967,17 +967,50 @@  static int nft_rule_snprintf_default(char *buf, size_t size, struct nft_rule *r,
 int nft_rule_snprintf(char *buf, size_t size, struct nft_rule *r,
 		       uint32_t type, uint32_t flags)
 {
+	int ret, len = size, offset = 0;
+	uint32_t noevent_flags = flags;
+
+	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTNEW);
+	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTDEL);
+	}
+
 	switch(type) {
 	case NFT_OUTPUT_DEFAULT:
-		return nft_rule_snprintf_default(buf, size, r, type, flags);
+		ret = nft_rule_snprintf_default(buf+offset, len, r, type,
+						noevent_flags);
+		break;
 	case NFT_OUTPUT_XML:
-		return nft_rule_snprintf_xml(buf, size, r, type, flags);
+		ret = nft_rule_snprintf_xml(buf+offset, len, r, type,
+					    noevent_flags);
+		break;
 	case NFT_OUTPUT_JSON:
-		return nft_rule_snprintf_json(buf, size, r, type, flags);
-	default:
+		ret = nft_rule_snprintf_json(buf+offset, len, r, type,
+					     noevent_flags);
 		break;
+	default:
+		return -1;
 	}
-	return -1;
+
+	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+
+	if ((flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) ||
+	    (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL))) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_closetag(type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
+	return offset;
 }
 EXPORT_SYMBOL(nft_rule_snprintf);
 
diff --git a/src/ruleset.c b/src/ruleset.c
index 3cbec09..2b249ef 100644
--- a/src/ruleset.c
+++ b/src/ruleset.c
@@ -765,6 +765,24 @@  nft_ruleset_do_snprintf(char *buf, size_t size, const struct nft_ruleset *rs,
 {
 	int ret, len = size, offset = 0;
 	void *prev = NULL;
+	uint32_t noevent_flags;
+
+	/* dont pass events flags to child calls of _snprintf() */
+	noevent_flags = flags;
+
+	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
+		ret = snprintf(buf+offset, size, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTNEW);
+	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
+		ret = snprintf(buf+offset, size, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTDEL);
+	}
 
 	ret = snprintf(buf+offset, size, "%s", nft_ruleset_o_opentag(type));
 	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
@@ -772,7 +790,7 @@  nft_ruleset_do_snprintf(char *buf, size_t size, const struct nft_ruleset *rs,
 	if (nft_ruleset_attr_is_set(rs, NFT_RULESET_ATTR_TABLELIST) &&
 	    (!nft_table_list_is_empty(rs->table_list))) {
 		ret = nft_ruleset_snprintf_table(buf+offset, len, rs,
-						 type, flags);
+						 type, noevent_flags);
 		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 
 		if (ret > 0)
@@ -786,7 +804,7 @@  nft_ruleset_do_snprintf(char *buf, size_t size, const struct nft_ruleset *rs,
 		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 
 		ret = nft_ruleset_snprintf_chain(buf+offset, len, rs,
-						 type, flags);
+						 type, noevent_flags);
 		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 
 		if (ret > 0)
@@ -800,7 +818,7 @@  nft_ruleset_do_snprintf(char *buf, size_t size, const struct nft_ruleset *rs,
 		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 
 		ret = nft_ruleset_snprintf_set(buf+offset, len, rs,
-					       type, flags);
+					       type, noevent_flags);
 		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 
 		if (ret > 0)
@@ -814,13 +832,20 @@  nft_ruleset_do_snprintf(char *buf, size_t size, const struct nft_ruleset *rs,
 		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 
 		ret = nft_ruleset_snprintf_rule(buf+offset, len, rs,
-						type, flags);
+						type, noevent_flags);
 		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 	}
 
 	ret = snprintf(buf+offset, size, "%s", nft_ruleset_o_closetag(type));
 	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
 
+	if ((flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) ||
+	    (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL))) {
+		ret = snprintf(buf+offset, size, "%s",
+			       nft_event_closetag(type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
 	return offset;
 }
 
@@ -989,13 +1014,32 @@  int nft_ruleset_fprintf(FILE *fp, const struct nft_ruleset *rs, uint32_t type,
 {
 	int len = 0, ret = 0;
 	void *prev = NULL;
+	uint32_t noevent_flags;
+
+	/* dont pass events flags to child calls of _snprintf() */
+	noevent_flags = flags;
+
+	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
+		ret = fprintf(fp, "%s",
+			      nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
+						type));
+		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTNEW);
+
+	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
+		ret = fprintf(fp, "%s",
+			      nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
+						type));
+		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTNEW);
+	}
 
 	ret = fprintf(fp, "%s", nft_ruleset_o_opentag(type));
 	NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
 	if ((nft_ruleset_attr_is_set(rs, NFT_RULESET_ATTR_TABLELIST)) &&
 	    (!nft_table_list_is_empty(rs->table_list))) {
-		ret = nft_ruleset_fprintf_tables(fp, rs, type, flags);
+		ret = nft_ruleset_fprintf_tables(fp, rs, type, noevent_flags);
 		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
 		if (ret > 0)
@@ -1007,7 +1051,7 @@  int nft_ruleset_fprintf(FILE *fp, const struct nft_ruleset *rs, uint32_t type,
 		ret = fprintf(fp, "%s", nft_ruleset_o_separator(prev, type));
 		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
-		ret = nft_ruleset_fprintf_chains(fp, rs, type, flags);
+		ret = nft_ruleset_fprintf_chains(fp, rs, type, noevent_flags);
 		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
 		if (ret > 0)
@@ -1019,7 +1063,7 @@  int nft_ruleset_fprintf(FILE *fp, const struct nft_ruleset *rs, uint32_t type,
 		ret = fprintf(fp, "%s", nft_ruleset_o_separator(prev, type));
 		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
-		ret = nft_ruleset_fprintf_sets(fp, rs, type, flags);
+		ret = nft_ruleset_fprintf_sets(fp, rs, type, noevent_flags);
 		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
 		if (ret > 0)
@@ -1031,13 +1075,19 @@  int nft_ruleset_fprintf(FILE *fp, const struct nft_ruleset *rs, uint32_t type,
 		ret = fprintf(fp, "%s", nft_ruleset_o_separator(prev, type));
 		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
-		ret = nft_ruleset_fprintf_rules(fp, rs, type, flags);
+		ret = nft_ruleset_fprintf_rules(fp, rs, type, noevent_flags);
 		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 	}
 
 	ret = fprintf(fp, "%s", nft_ruleset_o_closetag(type));
 	NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
 
+	if ((flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) ||
+	    (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL))) {
+		ret = fprintf(fp, "%s", nft_event_closetag(type));
+		NFT_FPRINTF_RETURN_OR_FIXLEN(ret, len);
+	}
+
 	return len;
 }
 EXPORT_SYMBOL(nft_ruleset_fprintf);
diff --git a/src/set.c b/src/set.c
index 550c262..59832aa 100644
--- a/src/set.c
+++ b/src/set.c
@@ -704,17 +704,49 @@  static int nft_set_snprintf_xml(char *buf, size_t size, struct nft_set *s,
 int nft_set_snprintf(char *buf, size_t size, struct nft_set *s,
 		     uint32_t type, uint32_t flags)
 {
+	int ret, len = size, offset = 0;
+	uint32_t noevent_flags = flags;
+
+	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTNEW);
+	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+		noevent_flags &= ~(1 << NFT_OUTPUT_FLAG_EVENTDEL);
+	}
+
 	switch(type) {
 	case NFT_OUTPUT_DEFAULT:
-		return nft_set_snprintf_default(buf, size, s, type, flags);
+		ret = nft_set_snprintf_default(buf+offset, len, s, type,
+					       noevent_flags);
+		break;
 	case NFT_OUTPUT_XML:
-		return nft_set_snprintf_xml(buf, size, s, flags);
+		ret = nft_set_snprintf_xml(buf+offset, len, s, noevent_flags);
+		break;
 	case NFT_OUTPUT_JSON:
-		return nft_set_snprintf_json(buf, size, s, type, flags);
-	default:
+		ret = nft_set_snprintf_json(buf+offset, len, s, type,
+					    noevent_flags);
 		break;
+	default:
+		return -1;
 	}
-	return -1;
+
+	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+
+	if ((flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) ||
+	    (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL))) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_closetag(type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
+	return offset;
 }
 EXPORT_SYMBOL(nft_set_snprintf);
 
diff --git a/src/set_elem.c b/src/set_elem.c
index a747ba6..9181a10 100644
--- a/src/set_elem.c
+++ b/src/set_elem.c
@@ -591,17 +591,44 @@  static int nft_set_elem_snprintf_xml(char *buf, size_t size,
 int nft_set_elem_snprintf(char *buf, size_t size, struct nft_set_elem *e,
 			   uint32_t type, uint32_t flags)
 {
+	int ret, len = size, offset = 0;
+
+	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
 	switch(type) {
 	case NFT_OUTPUT_DEFAULT:
-		return nft_set_elem_snprintf_default(buf, size, e);
+		ret = nft_set_elem_snprintf_default(buf+offset, len, e);
+		break;
 	case NFT_OUTPUT_XML:
-		return nft_set_elem_snprintf_xml(buf, size, e, flags);
+		ret = nft_set_elem_snprintf_xml(buf+offset, len, e, flags);
+		break;
 	case NFT_OUTPUT_JSON:
-		return nft_set_elem_snprintf_json(buf, size, e, flags);
-	default:
+		ret = nft_set_elem_snprintf_json(buf+offset, len, e, flags);
 		break;
+	default:
+		return -1;
 	}
-	return -1;
+
+	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+
+	if ((flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) ||
+	    (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL))) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_closetag(type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
+	return offset;
 }
 EXPORT_SYMBOL(nft_set_elem_snprintf);
 
diff --git a/src/table.c b/src/table.c
index 44e9a7b..82ca84d 100644
--- a/src/table.c
+++ b/src/table.c
@@ -441,17 +441,43 @@  static int nft_table_snprintf_default(char *buf, size_t size, struct nft_table *
 int nft_table_snprintf(char *buf, size_t size, struct nft_table *t,
 		       uint32_t type, uint32_t flags)
 {
+	int ret, len = size, offset = 0;
+
+	if (flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTNEW,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	} else if (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL)) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_opentag(NFT_OUTPUT_FLAG_EVENTDEL,
+						 type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
 	switch(type) {
 	case NFT_OUTPUT_DEFAULT:
-		return nft_table_snprintf_default(buf, size, t);
+		ret = nft_table_snprintf_default(buf+offset, len, t);
+		break;
 	case NFT_OUTPUT_XML:
-		return nft_table_snprintf_xml(buf, size, t);
+		ret = nft_table_snprintf_xml(buf+offset, len, t);
+		break;
 	case NFT_OUTPUT_JSON:
-		return nft_table_snprintf_json(buf, size, t);
-	default:
+		ret = nft_table_snprintf_json(buf+offset, len, t);
 		break;
+	default:
+		return -1;
 	}
-	return -1;
+	SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+
+	if ((flags & (1 << NFT_OUTPUT_FLAG_EVENTNEW)) ||
+	    (flags & (1 << NFT_OUTPUT_FLAG_EVENTDEL))) {
+		ret = snprintf(buf+offset, len, "%s",
+			       nft_event_closetag(type));
+		SNPRINTF_BUFFER_SIZE(ret, size, len, offset);
+	}
+
+	return offset;
 }
 EXPORT_SYMBOL(nft_table_snprintf);
 
diff --git a/src/utils.c b/src/utils.c
index 18917f5..870157a 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -212,6 +212,51 @@  int nft_fprintf(FILE *fp, void *obj, uint32_t type, uint32_t flags,
 	return ret;
 }
 
+const char *nft_event_opentag(uint32_t event, uint32_t format)
+{
+	switch (format) {
+	case NFT_OUTPUT_XML:
+		switch (event) {
+		case NFT_OUTPUT_FLAG_EVENTNEW:
+			return "<event><type>new</type>";
+		case NFT_OUTPUT_FLAG_EVENTDEL:
+			return "<event><type>destroy</type>";
+		default:
+			return "[unknown]";
+		}
+	case NFT_OUTPUT_JSON:
+		switch (event) {
+		case NFT_OUTPUT_FLAG_EVENTNEW:
+			return "{event:{type:\"new\",{\"";
+		case NFT_OUTPUT_FLAG_EVENTDEL:
+			return "{event:{type:\"destroy\",{\"";
+		default:
+			return "[unknown]";
+		}
+	default:
+		switch (event) {
+		case NFT_OUTPUT_FLAG_EVENTNEW:
+			return "[NEW] ";
+		case NFT_OUTPUT_FLAG_EVENTDEL:
+			return "[DEL] ";
+		default:
+			return "[unknown]";
+		}
+	}
+}
+
+const char *nft_event_closetag(uint32_t format)
+{
+	switch (format) {
+	case NFT_OUTPUT_XML:
+		return "</event>";
+	case NFT_OUTPUT_JSON:
+		return "}}}";
+	default:
+		return "";
+	}
+}
+
 void __nft_assert_fail(uint16_t attr, const char *filename, int line)
 {
 	fprintf(stderr, "libnftnl: attribute %d assertion failed in %s:%d\n",