diff mbox

[PATCHv4] netfilter: nf_tables: add insert operation

Message ID 1373960158.22759.7.camel@ice-age.regit.org
State Not Applicable
Headers show

Commit Message

Eric Leblond July 16, 2013, 7:35 a.m. UTC 
Hello Pablo,

Le mardi 16 juillet 2013 à 01:57 +0200, Pablo Neira Ayuso a écrit :
> Hi Eric,
> 
> On Mon, Jul 15, 2013 at 07:27:54PM +0200, Eric Leblond wrote:
> > Hi,
> > 
> > Le lundi 15 juillet 2013 à 12:48 +0200, Pablo Neira Ayuso a écrit :
> > > Hi Eric,
> > > 
> > > On Tue, Jul 09, 2013 at 12:56:17AM +0200, Eric Leblond wrote:
> > > > This patch adds a new rule attribute NFTA_RULE_POSITION which is
> > > > used to store the position of a rule relatively to the others.
> > > > By providing a create command and specifying a position, the rule is
> > > > inserted after the rule with the handle equal to the provided
> > > > position.
> > > > Regarding notification, the position attribute is added to specify
> > > > the handle of the previous rule in append mode and the handle of
> > > > the next rule in the other case.
> > > > 
> > > > Signed-off-by: Eric Leblond <eric@regit.org>
> > > > ---
> > > >  include/uapi/linux/netfilter/nf_tables.h |  1 +
> > > >  net/netfilter/nf_tables_api.c            | 46 +++++++++++++++++++++++++++++---
> > > >  2 files changed, 43 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> > > > index d40a7f9..d9bf8ea 100644
> > > > --- a/include/uapi/linux/netfilter/nf_tables.h
> > > > +++ b/include/uapi/linux/netfilter/nf_tables.h
> > > > @@ -143,6 +143,7 @@ enum nft_rule_attributes {
> > > >  	NFTA_RULE_EXPRESSIONS,
> > > >  	NFTA_RULE_FLAGS,
> > > >  	NFTA_RULE_COMPAT,
> > > > +	NFTA_RULE_POSITION,
> > > >  	__NFTA_RULE_MAX
> > > >  };
> > > >  #define NFTA_RULE_MAX		(__NFTA_RULE_MAX - 1)
> > > > diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> > > > index b00aca8..012eb1f 100644
> > > > --- a/net/netfilter/nf_tables_api.c
> > > > +++ b/net/netfilter/nf_tables_api.c
> > > > @@ -1267,6 +1267,7 @@ static const struct nla_policy nft_rule_policy[NFTA_RULE_MAX + 1] = {
> > > >  	[NFTA_RULE_EXPRESSIONS]	= { .type = NLA_NESTED },
> > > >  	[NFTA_RULE_FLAGS]	= { .type = NLA_U32 },
> > > >  	[NFTA_RULE_COMPAT]	= { .type = NLA_NESTED },
> > > > +	[NFTA_RULE_POSITION]	= { .type = NLA_U64 },
> > > >  };
> > > >  
> > > >  static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > > @@ -1279,6 +1280,7 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > >  	struct nfgenmsg *nfmsg;
> > > >  	const struct nft_expr *expr, *next;
> > > >  	struct nlattr *list;
> > > > +	const struct nft_rule *prule;
> > > >  
> > > >  	event |= NFNL_SUBSYS_NFTABLES << 8;
> > > >  	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg),
> > > > @@ -1298,6 +1300,26 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > >  	if (nla_put_be64(skb, NFTA_RULE_HANDLE, cpu_to_be64(rule->handle)))
> > > >  		goto nla_put_failure;
> > > >  
> > > > +	if (flags & NLM_F_APPEND) {
> > > > +		if ((event != NFT_MSG_DELRULE) &&
> > > > +		    (rule->list.prev != &chain->rules)) {
> > > > +			prule = list_entry(rule->list.prev,
> > > > +					   struct nft_rule, list);
> > > > +			if (nla_put_be64(skb, NFTA_RULE_POSITION,
> > > > +					 cpu_to_be64(prule->handle)))
> > > > +				goto nla_put_failure;
> > > > +		}
> > > 
> > > This looks good but I think we can simplify this to always use .prev.
> > > 
> > > 1) Append: we use .prev. If it's the first rule in the list, skip
> > >    position attribute.
> > > 
> > > 2) Insert: never dump position attribute as it is always the first
> > >    rule in the list.
> > > 
> > > 3) At position X: use .prev. If it's the first rule in the list, skip.
> > > 
> > > That should allows us to remove the else branch below and it should
> > > simplify the semantics of NFTA_RULE_POSITION as well.
> > 
> > This code is not pretty and I understand your point but we have two type
> > of operations:
> >       * Insert before
> >       * Append after
> > In both cases, the presence of the NFTA_RULE_POSITION attribute is
> > triggering the switch to this mode. And I think this is a convenient way
> > to update the API.
> 
> I see. Then we need to save the append flag to report events correctly
> in the commit path for the "insert after" case, according to this
> approach (that's should be easy to resolve though with a follow up
> patch).


IMHO, it is already there. At start of nf_tables_fill_rule_info, we are
doing:

	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg),
			flags);

So flags is used as flag inside nlh. And we can get the information
during event by checking (nlh->nlmsg_flags & NLM_F_APPEND). I've done
some tests with the attached patch and it seems to work well.

So events get insert/append information as well as position. This should
be enough for event listeners to follow ruleset evolution.

> > Furthermore, inside nf_tables_fill_rule_info() we don't have any
> > information to decide that we are in "position X".
> 
> But we know the handle of our .prev node for that new rule we added,
> that can be used to report back our relative location to it, ie.
> always return the previous node.
> 
> This however results in reporting back a different handle via the
> event notification in the "insert after" case (instead of the original
> handle passed via the rule_position attribute).

Yes, getting insert/append information and position is better.

> > Only solution to switch to the method you describe would be to
> > introduce a new operation and it seems that was is wanted (it was
> > said in initial discussion).
> 
> Sure, I just wanted to discuss the nf_tables_fill_rule_info path, not
> questioning the entire patch.

Cool :)

BR,
--
Eric

Comments

Pablo Neira Ayuso July 16, 2013, 10 a.m. UTC | #1 
On Tue, Jul 16, 2013 at 09:35:58AM +0200, Eric Leblond wrote:
> Hello Pablo,
> 
> Le mardi 16 juillet 2013 à 01:57 +0200, Pablo Neira Ayuso a écrit :
> > Hi Eric,
> > 
> > On Mon, Jul 15, 2013 at 07:27:54PM +0200, Eric Leblond wrote:
> > > Hi,
> > > 
> > > Le lundi 15 juillet 2013 à 12:48 +0200, Pablo Neira Ayuso a écrit :
> > > > Hi Eric,
> > > > 
> > > > On Tue, Jul 09, 2013 at 12:56:17AM +0200, Eric Leblond wrote:
> > > > > This patch adds a new rule attribute NFTA_RULE_POSITION which is
> > > > > used to store the position of a rule relatively to the others.
> > > > > By providing a create command and specifying a position, the rule is
> > > > > inserted after the rule with the handle equal to the provided
> > > > > position.
> > > > > Regarding notification, the position attribute is added to specify
> > > > > the handle of the previous rule in append mode and the handle of
> > > > > the next rule in the other case.
> > > > > 
> > > > > Signed-off-by: Eric Leblond <eric@regit.org>
> > > > > ---
> > > > >  include/uapi/linux/netfilter/nf_tables.h |  1 +
> > > > >  net/netfilter/nf_tables_api.c            | 46 +++++++++++++++++++++++++++++---
> > > > >  2 files changed, 43 insertions(+), 4 deletions(-)
> > > > > 
> > > > > diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> > > > > index d40a7f9..d9bf8ea 100644
> > > > > --- a/include/uapi/linux/netfilter/nf_tables.h
> > > > > +++ b/include/uapi/linux/netfilter/nf_tables.h
> > > > > @@ -143,6 +143,7 @@ enum nft_rule_attributes {
> > > > >  	NFTA_RULE_EXPRESSIONS,
> > > > >  	NFTA_RULE_FLAGS,
> > > > >  	NFTA_RULE_COMPAT,
> > > > > +	NFTA_RULE_POSITION,
> > > > >  	__NFTA_RULE_MAX
> > > > >  };
> > > > >  #define NFTA_RULE_MAX		(__NFTA_RULE_MAX - 1)
> > > > > diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> > > > > index b00aca8..012eb1f 100644
> > > > > --- a/net/netfilter/nf_tables_api.c
> > > > > +++ b/net/netfilter/nf_tables_api.c
> > > > > @@ -1267,6 +1267,7 @@ static const struct nla_policy nft_rule_policy[NFTA_RULE_MAX + 1] = {
> > > > >  	[NFTA_RULE_EXPRESSIONS]	= { .type = NLA_NESTED },
> > > > >  	[NFTA_RULE_FLAGS]	= { .type = NLA_U32 },
> > > > >  	[NFTA_RULE_COMPAT]	= { .type = NLA_NESTED },
> > > > > +	[NFTA_RULE_POSITION]	= { .type = NLA_U64 },
> > > > >  };
> > > > >  
> > > > >  static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > > > @@ -1279,6 +1280,7 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > > >  	struct nfgenmsg *nfmsg;
> > > > >  	const struct nft_expr *expr, *next;
> > > > >  	struct nlattr *list;
> > > > > +	const struct nft_rule *prule;
> > > > >  
> > > > >  	event |= NFNL_SUBSYS_NFTABLES << 8;
> > > > >  	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg),
> > > > > @@ -1298,6 +1300,26 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > > >  	if (nla_put_be64(skb, NFTA_RULE_HANDLE, cpu_to_be64(rule->handle)))
> > > > >  		goto nla_put_failure;
> > > > >  
> > > > > +	if (flags & NLM_F_APPEND) {
> > > > > +		if ((event != NFT_MSG_DELRULE) &&
> > > > > +		    (rule->list.prev != &chain->rules)) {
> > > > > +			prule = list_entry(rule->list.prev,
> > > > > +					   struct nft_rule, list);
> > > > > +			if (nla_put_be64(skb, NFTA_RULE_POSITION,
> > > > > +					 cpu_to_be64(prule->handle)))
> > > > > +				goto nla_put_failure;
> > > > > +		}
> > > > 
> > > > This looks good but I think we can simplify this to always use .prev.
> > > > 
> > > > 1) Append: we use .prev. If it's the first rule in the list, skip
> > > >    position attribute.
> > > > 
> > > > 2) Insert: never dump position attribute as it is always the first
> > > >    rule in the list.
> > > > 
> > > > 3) At position X: use .prev. If it's the first rule in the list, skip.
> > > > 
> > > > That should allows us to remove the else branch below and it should
> > > > simplify the semantics of NFTA_RULE_POSITION as well.
> > > 
> > > This code is not pretty and I understand your point but we have two type
> > > of operations:
> > >       * Insert before
> > >       * Append after
> > > In both cases, the presence of the NFTA_RULE_POSITION attribute is
> > > triggering the switch to this mode. And I think this is a convenient way
> > > to update the API.
> > 
> > I see. Then we need to save the append flag to report events correctly
> > in the commit path for the "insert after" case, according to this
> > approach (that's should be easy to resolve though with a follow up
> > patch).
> 
> 
> IMHO, it is already there. At start of nf_tables_fill_rule_info, we are
> doing:
> 
> 	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg),
> 			flags);
> 
> So flags is used as flag inside nlh. And we can get the information
> during event by checking (nlh->nlmsg_flags & NLM_F_APPEND). I've done
> some tests with the attached patch and it seems to work well.

Please, see nf_tables_commit. In that path nf_tables_rule_notify does
not get those flags at this moment, so it's returning its position in
the insert fashion, ie. pointing to .next.

The problem with pointing to the .next node in the commit path is we
are sure that .prev points to an existing rule. However, .next may point
to stale rule. So I think we have to notify the position always
relative to the .prev pointer to get this working in the commit path.

Regards.
--
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Eric Leblond July 16, 2013, 10:07 a.m. UTC | #2 
Hi,

Le mardi 16 juillet 2013 à 12:00 +0200, Pablo Neira Ayuso a écrit :
> On Tue, Jul 16, 2013 at 09:35:58AM +0200, Eric Leblond wrote:
> > Hello Pablo,
> > 
> > Le mardi 16 juillet 2013 à 01:57 +0200, Pablo Neira Ayuso a écrit :
> > > Hi Eric,
> > > 
> > > On Mon, Jul 15, 2013 at 07:27:54PM +0200, Eric Leblond wrote:
> > > > Hi,
> > > > 
> > > > Le lundi 15 juillet 2013 à 12:48 +0200, Pablo Neira Ayuso a écrit :
> > > > > Hi Eric,
> > > > > 
> > > > > On Tue, Jul 09, 2013 at 12:56:17AM +0200, Eric Leblond wrote:
> > > > > > This patch adds a new rule attribute NFTA_RULE_POSITION which is
> > > > > > used to store the position of a rule relatively to the others.
> > > > > > By providing a create command and specifying a position, the rule is
> > > > > > inserted after the rule with the handle equal to the provided
> > > > > > position.
> > > > > > Regarding notification, the position attribute is added to specify
> > > > > > the handle of the previous rule in append mode and the handle of
> > > > > > the next rule in the other case.
> > > > > > 
> > > > > > Signed-off-by: Eric Leblond <eric@regit.org>
> > > > > > ---
> > > > > >  include/uapi/linux/netfilter/nf_tables.h |  1 +
> > > > > >  net/netfilter/nf_tables_api.c            | 46 +++++++++++++++++++++++++++++---
> > > > > >  2 files changed, 43 insertions(+), 4 deletions(-)
> > > > > > 
> > > > > > diff --git a/include/uapi/linux/netfilter/nf_tables.h b/include/uapi/linux/netfilter/nf_tables.h
> > > > > > index d40a7f9..d9bf8ea 100644
> > > > > > --- a/include/uapi/linux/netfilter/nf_tables.h
> > > > > > +++ b/include/uapi/linux/netfilter/nf_tables.h
> > > > > > @@ -143,6 +143,7 @@ enum nft_rule_attributes {
> > > > > >  	NFTA_RULE_EXPRESSIONS,
> > > > > >  	NFTA_RULE_FLAGS,
> > > > > >  	NFTA_RULE_COMPAT,
> > > > > > +	NFTA_RULE_POSITION,
> > > > > >  	__NFTA_RULE_MAX
> > > > > >  };
> > > > > >  #define NFTA_RULE_MAX		(__NFTA_RULE_MAX - 1)
> > > > > > diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> > > > > > index b00aca8..012eb1f 100644
> > > > > > --- a/net/netfilter/nf_tables_api.c
> > > > > > +++ b/net/netfilter/nf_tables_api.c
> > > > > > @@ -1267,6 +1267,7 @@ static const struct nla_policy nft_rule_policy[NFTA_RULE_MAX + 1] = {
> > > > > >  	[NFTA_RULE_EXPRESSIONS]	= { .type = NLA_NESTED },
> > > > > >  	[NFTA_RULE_FLAGS]	= { .type = NLA_U32 },
> > > > > >  	[NFTA_RULE_COMPAT]	= { .type = NLA_NESTED },
> > > > > > +	[NFTA_RULE_POSITION]	= { .type = NLA_U64 },
> > > > > >  };
> > > > > >  
> > > > > >  static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > > > > @@ -1279,6 +1280,7 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > > > >  	struct nfgenmsg *nfmsg;
> > > > > >  	const struct nft_expr *expr, *next;
> > > > > >  	struct nlattr *list;
> > > > > > +	const struct nft_rule *prule;
> > > > > >  
> > > > > >  	event |= NFNL_SUBSYS_NFTABLES << 8;
> > > > > >  	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg),
> > > > > > @@ -1298,6 +1300,26 @@ static int nf_tables_fill_rule_info(struct sk_buff *skb, u32 portid, u32 seq,
> > > > > >  	if (nla_put_be64(skb, NFTA_RULE_HANDLE, cpu_to_be64(rule->handle)))
> > > > > >  		goto nla_put_failure;
> > > > > >  
> > > > > > +	if (flags & NLM_F_APPEND) {
> > > > > > +		if ((event != NFT_MSG_DELRULE) &&
> > > > > > +		    (rule->list.prev != &chain->rules)) {
> > > > > > +			prule = list_entry(rule->list.prev,
> > > > > > +					   struct nft_rule, list);
> > > > > > +			if (nla_put_be64(skb, NFTA_RULE_POSITION,
> > > > > > +					 cpu_to_be64(prule->handle)))
> > > > > > +				goto nla_put_failure;
> > > > > > +		}
> > > > > 
> > > > > This looks good but I think we can simplify this to always use .prev.
> > > > > 
> > > > > 1) Append: we use .prev. If it's the first rule in the list, skip
> > > > >    position attribute.
> > > > > 
> > > > > 2) Insert: never dump position attribute as it is always the first
> > > > >    rule in the list.
> > > > > 
> > > > > 3) At position X: use .prev. If it's the first rule in the list, skip.
> > > > > 
> > > > > That should allows us to remove the else branch below and it should
> > > > > simplify the semantics of NFTA_RULE_POSITION as well.
> > > > 
> > > > This code is not pretty and I understand your point but we have two type
> > > > of operations:
> > > >       * Insert before
> > > >       * Append after
> > > > In both cases, the presence of the NFTA_RULE_POSITION attribute is
> > > > triggering the switch to this mode. And I think this is a convenient way
> > > > to update the API.
> > > 
> > > I see. Then we need to save the append flag to report events correctly
> > > in the commit path for the "insert after" case, according to this
> > > approach (that's should be easy to resolve though with a follow up
> > > patch).
> > 
> > 
> > IMHO, it is already there. At start of nf_tables_fill_rule_info, we are
> > doing:
> > 
> > 	nlh = nlmsg_put(skb, portid, seq, event, sizeof(struct nfgenmsg),
> > 			flags);
> > 
> > So flags is used as flag inside nlh. And we can get the information
> > during event by checking (nlh->nlmsg_flags & NLM_F_APPEND). I've done
> > some tests with the attached patch and it seems to work well.
> 
> Please, see nf_tables_commit. In that path nf_tables_rule_notify does
> not get those flags at this moment, so it's returning its position in
> the insert fashion, ie. pointing to .next.
> 
> The problem with pointing to the .next node in the commit path is we
> are sure that .prev points to an existing rule. However, .next may point
> to stale rule. So I think we have to notify the position always
> relative to the .prev pointer to get this working in the commit path.

Thanks a lot for the clarification. I'll update the patch.

BR,
--
Eric
diff mbox

Patch

From 86e6e09ebbe2b770547034c2cb6a2239f79f1ce4 Mon Sep 17 00:00:00 2001
From: Eric Leblond <eric@regit.org>
Date: Tue, 16 Jul 2013 09:12:19 +0200
Subject: [PATCH] after before

Signed-off-by: Eric Leblond <eric@regit.org>
---
 examples/nft-events.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/examples/nft-events.c b/examples/nft-events.c
index 5550c70..5bbdce4 100644
--- a/examples/nft-events.c
+++ b/examples/nft-events.c
@@ -63,6 +63,10 @@  static int rule_cb(const struct nlmsghdr *nlh, int type)
 		goto err_free;
 	}
 
+	if (nlh->nlmsg_flags & NLM_F_APPEND)
+		printf("AFTER ");
+	else
+		printf("BEFORE ");
 	nft_rule_snprintf(buf, sizeof(buf), t, NFT_RULE_O_DEFAULT, 0);
 	printf("[%s]\t%s\n", type == NFT_MSG_NEWRULE ? "NEW" : "DEL", buf);
 
-- 
1.8.3.2