[PATCH libnftnl] src: restore static array with expression operations

[PATCH libnftnl] src: restore static array with expression operations

[Pablo Neira Ayuso]

We cannot use __attribute__((constructor)) to register the supported
expressions in runtime when the library is statically linked. This lead
us to some explicit libnftnl_init() function that needs to be called
from the main() function of the client program.

This patch reverts 4dd0772 ("expr: use __attribute__((constructor)) to
register expression").

Reported-by: Laurent Bercot <ska-devel@skarnet.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/expr_ops.h   |    3 ---
 include/utils.h      |    1 -
 src/expr/bitwise.c   |    5 -----
 src/expr/byteorder.c |    5 -----
 src/expr/cmp.c       |    4 ----
 src/expr/counter.c   |    5 -----
 src/expr/ct.c        |    5 -----
 src/expr/exthdr.c    |    5 -----
 src/expr/immediate.c |    5 -----
 src/expr/limit.c     |    5 -----
 src/expr/log.c       |    5 -----
 src/expr/lookup.c    |    5 -----
 src/expr/masq.c      |    5 -----
 src/expr/match.c     |    5 -----
 src/expr/meta.c      |    5 -----
 src/expr/nat.c       |    5 -----
 src/expr/payload.c   |    5 -----
 src/expr/queue.c     |    5 -----
 src/expr/redir.c     |    5 -----
 src/expr/reject.c    |    5 -----
 src/expr/target.c    |    5 -----
 src/expr_ops.c       |   58 +++++++++++++++++++++++++++++++++++++++++---------
 22 files changed, 48 insertions(+), 108 deletions(-)

diff --git a/include/expr_ops.h b/include/expr_ops.h
index ea5defd..08cf57f 100644
--- a/include/expr_ops.h
+++ b/include/expr_ops.h
@@ -9,8 +9,6 @@ struct nlmsghdr;
 struct nft_rule_expr;
 
 struct expr_ops {
-	struct list_head head;
-
 	const char *name;
 	uint32_t alloc_len;
 	int	max_attr;
@@ -26,7 +24,6 @@ struct expr_ops {
 			      struct nft_parse_err *err);
 };
 
-void nft_expr_ops_register(struct expr_ops *ops);
 struct expr_ops *nft_expr_ops_lookup(const char *name);
 
 #define nft_expr_data(ops) (void *)ops->data
diff --git a/include/utils.h b/include/utils.h
index 1801108..380b020 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -15,7 +15,6 @@
 #	define EXPORT_SYMBOL
 #endif
 
-#define __init		__attribute__((constructor))
 #define __noreturn	__attribute__((__noreturn__))
 
 #define xfree(ptr)	free((void *)ptr);
diff --git a/src/expr/bitwise.c b/src/expr/bitwise.c
index 3c4a2e4..f0851b0 100644
--- a/src/expr/bitwise.c
+++ b/src/expr/bitwise.c
@@ -322,8 +322,3 @@ struct expr_ops expr_ops_bitwise = {
 	.xml_parse	= nft_rule_expr_bitwise_xml_parse,
 	.json_parse	= nft_rule_expr_bitwise_json_parse,
 };
-
-static void __init expr_bitwise(void)
-{
-	nft_expr_ops_register(&expr_ops_bitwise);
-}
diff --git a/src/expr/byteorder.c b/src/expr/byteorder.c
index a16b145..81e5278 100644
--- a/src/expr/byteorder.c
+++ b/src/expr/byteorder.c
@@ -338,8 +338,3 @@ struct expr_ops expr_ops_byteorder = {
 	.xml_parse	= nft_rule_expr_byteorder_xml_parse,
 	.json_parse	= nft_rule_expr_byteorder_json_parse,
 };
-
-static void __init expr_byteorder_init(void)
-{
-	nft_expr_ops_register(&expr_ops_byteorder);
-}
diff --git a/src/expr/cmp.c b/src/expr/cmp.c
index ea51b83..3536332 100644
--- a/src/expr/cmp.c
+++ b/src/expr/cmp.c
@@ -305,7 +305,3 @@ struct expr_ops expr_ops_cmp = {
 	.xml_parse	= nft_rule_expr_cmp_xml_parse,
 	.json_parse	= nft_rule_expr_cmp_json_parse,
 };
-static void __init expr_cmp_init(void)
-{
-	nft_expr_ops_register(&expr_ops_cmp);
-}
diff --git a/src/expr/counter.c b/src/expr/counter.c
index a190863..55fe526 100644
--- a/src/expr/counter.c
+++ b/src/expr/counter.c
@@ -210,8 +210,3 @@ struct expr_ops expr_ops_counter = {
 	.xml_parse	= nft_rule_expr_counter_xml_parse,
 	.json_parse	= nft_rule_expr_counter_json_parse,
 };
-
-static void __init expr_counter_init(void)
-{
-	nft_expr_ops_register(&expr_ops_counter);
-}
diff --git a/src/expr/ct.c b/src/expr/ct.c
index c15bf42..b808e03 100644
--- a/src/expr/ct.c
+++ b/src/expr/ct.c
@@ -381,8 +381,3 @@ struct expr_ops expr_ops_ct = {
 	.xml_parse	= nft_rule_expr_ct_xml_parse,
 	.json_parse	= nft_rule_expr_ct_json_parse,
 };
-
-static void __init expr_ct_init(void)
-{
-	nft_expr_ops_register(&expr_ops_ct);
-}
diff --git a/src/expr/exthdr.c b/src/expr/exthdr.c
index 615fec6..a2541b4 100644
--- a/src/expr/exthdr.c
+++ b/src/expr/exthdr.c
@@ -316,8 +316,3 @@ struct expr_ops expr_ops_exthdr = {
 	.xml_parse	= nft_rule_expr_exthdr_xml_parse,
 	.json_parse	= nft_rule_expr_exthdr_json_parse,
 };
-
-static void __init expr_exthdr_init(void)
-{
-	nft_expr_ops_register(&expr_ops_exthdr);
-}
diff --git a/src/expr/immediate.c b/src/expr/immediate.c
index b6cde0a..692d9e9 100644
--- a/src/expr/immediate.c
+++ b/src/expr/immediate.c
@@ -321,8 +321,3 @@ struct expr_ops expr_ops_immediate = {
 	.xml_parse	= nft_rule_expr_immediate_xml_parse,
 	.json_parse	= nft_rule_expr_immediate_json_parse,
 };
-
-static void __init expr_immediate_init(void)
-{
-	nft_expr_ops_register(&expr_ops_immediate);
-}
diff --git a/src/expr/limit.c b/src/expr/limit.c
index f9331b3..3ad246e 100644
--- a/src/expr/limit.c
+++ b/src/expr/limit.c
@@ -220,8 +220,3 @@ struct expr_ops expr_ops_limit = {
 	.xml_parse	= nft_rule_expr_limit_xml_parse,
 	.json_parse	= nft_rule_expr_limit_json_parse,
 };
-
-static void __init expr_limit_init(void)
-{
-	nft_expr_ops_register(&expr_ops_limit);
-}
diff --git a/src/expr/log.c b/src/expr/log.c
index 776c7fc..19bef56 100644
--- a/src/expr/log.c
+++ b/src/expr/log.c
@@ -345,8 +345,3 @@ struct expr_ops expr_ops_log = {
 	.xml_parse	= nft_rule_expr_log_xml_parse,
 	.json_parse	= nft_rule_expr_log_json_parse,
 };
-
-static void __init expr_log_init(void)
-{
-	nft_expr_ops_register(&expr_ops_log);
-}
diff --git a/src/expr/lookup.c b/src/expr/lookup.c
index 57eba1b..b2f0aa4 100644
--- a/src/expr/lookup.c
+++ b/src/expr/lookup.c
@@ -270,8 +270,3 @@ struct expr_ops expr_ops_lookup = {
 	.xml_parse	= nft_rule_expr_lookup_xml_parse,
 	.json_parse	= nft_rule_expr_lookup_json_parse,
 };
-
-static void __init expr_lookup_init(void)
-{
-	nft_expr_ops_register(&expr_ops_lookup);
-}
diff --git a/src/expr/masq.c b/src/expr/masq.c
index 79f5185..e25587f 100644
--- a/src/expr/masq.c
+++ b/src/expr/masq.c
@@ -184,8 +184,3 @@ struct expr_ops expr_ops_masq = {
 	.xml_parse	= nft_rule_expr_masq_xml_parse,
 	.json_parse	= nft_rule_expr_masq_json_parse,
 };
-
-static void __init expr_masq_init(void)
-{
-	nft_expr_ops_register(&expr_ops_masq);
-}
diff --git a/src/expr/match.c b/src/expr/match.c
index 45e7caf..e101c1f 100644
--- a/src/expr/match.c
+++ b/src/expr/match.c
@@ -253,8 +253,3 @@ struct expr_ops expr_ops_match = {
 	.xml_parse 	= nft_rule_expr_match_xml_parse,
 	.json_parse 	= nft_rule_expr_match_json_parse,
 };
-
-static void __init expr_match_init(void)
-{
-	nft_expr_ops_register(&expr_ops_match);
-}
diff --git a/src/expr/meta.c b/src/expr/meta.c
index 2f5cddc..cee09dd 100644
--- a/src/expr/meta.c
+++ b/src/expr/meta.c
@@ -307,8 +307,3 @@ struct expr_ops expr_ops_meta = {
 	.xml_parse 	= nft_rule_expr_meta_xml_parse,
 	.json_parse 	= nft_rule_expr_meta_json_parse,
 };
-
-static void __init expr_meta_init(void)
-{
-	nft_expr_ops_register(&expr_ops_meta);
-}
diff --git a/src/expr/nat.c b/src/expr/nat.c
index e36d023..f888dfa 100644
--- a/src/expr/nat.c
+++ b/src/expr/nat.c
@@ -416,8 +416,3 @@ struct expr_ops expr_ops_nat = {
 	.xml_parse	= nft_rule_expr_nat_xml_parse,
 	.json_parse	= nft_rule_expr_nat_json_parse,
 };
-
-static void __init expr_nat_init(void)
-{
-	nft_expr_ops_register(&expr_ops_nat);
-}
diff --git a/src/expr/payload.c b/src/expr/payload.c
index 61e88a9..52bea19 100644
--- a/src/expr/payload.c
+++ b/src/expr/payload.c
@@ -297,8 +297,3 @@ struct expr_ops expr_ops_payload = {
 	.xml_parse	= nft_rule_expr_payload_xml_parse,
 	.json_parse	= nft_rule_expr_payload_json_parse,
 };
-
-static void __init expr_payload_init(void)
-{
-	nft_expr_ops_register(&expr_ops_payload);
-}
diff --git a/src/expr/queue.c b/src/expr/queue.c
index dbae701..5e2a49e 100644
--- a/src/expr/queue.c
+++ b/src/expr/queue.c
@@ -255,8 +255,3 @@ struct expr_ops expr_ops_queue = {
 	.xml_parse	= nft_rule_expr_queue_xml_parse,
 	.json_parse	= nft_rule_expr_queue_json_parse,
 };
-
-static void __init expr_queue_init(void)
-{
-	nft_expr_ops_register(&expr_ops_queue);
-}
diff --git a/src/expr/redir.c b/src/expr/redir.c
index a1be181..b6adf88 100644
--- a/src/expr/redir.c
+++ b/src/expr/redir.c
@@ -254,8 +254,3 @@ struct expr_ops expr_ops_redir = {
 	.xml_parse	= nft_rule_expr_redir_xml_parse,
 	.json_parse	= nft_rule_expr_redir_json_parse,
 };
-
-static void __init expr_redir_init(void)
-{
-	nft_expr_ops_register(&expr_ops_redir);
-}
diff --git a/src/expr/reject.c b/src/expr/reject.c
index cd62cbe..a9c13d5 100644
--- a/src/expr/reject.c
+++ b/src/expr/reject.c
@@ -211,8 +211,3 @@ struct expr_ops expr_ops_reject = {
 	.xml_parse	= nft_rule_expr_reject_xml_parse,
 	.json_parse	= nft_rule_expr_reject_json_parse,
 };
-
-static void __init expr_reject_init(void)
-{
-	nft_expr_ops_register(&expr_ops_reject);
-}
diff --git a/src/expr/target.c b/src/expr/target.c
index 16e9e83..65c1ce0 100644
--- a/src/expr/target.c
+++ b/src/expr/target.c
@@ -254,8 +254,3 @@ struct expr_ops expr_ops_target = {
 	.xml_parse	= nft_rule_expr_target_xml_parse,
 	.json_parse	= nft_rule_expr_target_json_parse,
 };
-
-static void __init expr_target_init(void)
-{
-	nft_expr_ops_register(&expr_ops_target);
-}
diff --git a/src/expr_ops.c b/src/expr_ops.c
index d0315a3..9d8f3c9 100644
--- a/src/expr_ops.c
+++ b/src/expr_ops.c
@@ -3,21 +3,59 @@
 
 #include "expr_ops.h"
 
-static LIST_HEAD(expr_ops_list);
+/* Unfortunately, __attribute__((constructor)) breaks library static link */
+extern struct expr_ops expr_ops_bitwise;
+extern struct expr_ops expr_ops_byteorder;
+extern struct expr_ops expr_ops_cmp;
+extern struct expr_ops expr_ops_counter;
+extern struct expr_ops expr_ops_ct;
+extern struct expr_ops expr_ops_exthdr;
+extern struct expr_ops expr_ops_immediate;
+extern struct expr_ops expr_ops_limit;
+extern struct expr_ops expr_ops_log;
+extern struct expr_ops expr_ops_lookup;
+extern struct expr_ops expr_ops_masq;
+extern struct expr_ops expr_ops_match;
+extern struct expr_ops expr_ops_meta;
+extern struct expr_ops expr_ops_nat;
+extern struct expr_ops expr_ops_payload;
+extern struct expr_ops expr_ops_redir;
+extern struct expr_ops expr_ops_reject;
+extern struct expr_ops expr_ops_queue;
+extern struct expr_ops expr_ops_target;
 
-void nft_expr_ops_register(struct expr_ops *ops)
-{
-	list_add_tail(&ops->head, &expr_ops_list);
-}
+static struct expr_ops *expr_ops[] = {
+	&expr_ops_bitwise,
+	&expr_ops_byteorder,
+	&expr_ops_cmp,
+	&expr_ops_counter,
+	&expr_ops_ct,
+	&expr_ops_exthdr,
+	&expr_ops_immediate,
+	&expr_ops_limit,
+	&expr_ops_log,
+	&expr_ops_lookup,
+	&expr_ops_masq,
+	&expr_ops_match,
+	&expr_ops_meta,
+	&expr_ops_nat,
+	&expr_ops_payload,
+	&expr_ops_redir,
+	&expr_ops_reject,
+	&expr_ops_queue,
+	&expr_ops_target,
+	NULL,
+};
 
 struct expr_ops *nft_expr_ops_lookup(const char *name)
 {
-	struct expr_ops *ops;
+	int i = 0;
 
-	list_for_each_entry(ops, &expr_ops_list, head) {
-		if (strcmp(ops->name, name) == 0)
-			return ops;
-	}
+	while (expr_ops[i] != NULL) {
+		if (strcmp(expr_ops[i]->name, name) == 0)
+			return expr_ops[i];
 
+		i++;
+	}
 	return NULL;
 }
-- 
1.7.10.4

Re: [PATCH libnftnl] src: restore static array with expression operations

[Patrick McHardy]

On 23.03, Pablo Neira Ayuso wrote:
> We cannot use __attribute__((constructor)) to register the supported
> expressions in runtime when the library is statically linked. This lead
> us to some explicit libnftnl_init() function that needs to be called
> from the main() function of the client program.

Just wondering, why not? They should still be invoked, right?

> This patch reverts 4dd0772 ("expr: use __attribute__((constructor)) to
> register expression").
> 
> Reported-by: Laurent Bercot <ska-devel@skarnet.org>
> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Re: [PATCH libnftnl] src: restore static array with expression operations

[Pablo Neira Ayuso]

On Mon, Mar 23, 2015 at 11:44:11AM +0000, Patrick McHardy wrote:
> On 23.03, Pablo Neira Ayuso wrote:
> > We cannot use __attribute__((constructor)) to register the supported
> > expressions in runtime when the library is statically linked. This lead
> > us to some explicit libnftnl_init() function that needs to be called
> > from the main() function of the client program.
> 
> Just wondering, why not? They should still be invoked, right?

This seems to run when the shared library is loaded. When the build is
static, that never happens.

In iptables, we're resolving this with an init_extensions() function
that is called from main() so these are registered in run-time. I
would like to skip such explicit call from the client programs.

If you have any better solution, let me know. I actually liked that
the expression class, including its registration was self-contained
:-(.

> > This patch reverts 4dd0772 ("expr: use __attribute__((constructor)) to
> > register expression").
> > 
> > Reported-by: Laurent Bercot <ska-devel@skarnet.org>
> > Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Re: [PATCH libnftnl] src: restore static array with expression operations

[Patrick McHardy]

On 23.03, Pablo Neira Ayuso wrote:
> On Mon, Mar 23, 2015 at 11:44:11AM +0000, Patrick McHardy wrote:
> > On 23.03, Pablo Neira Ayuso wrote:
> > > We cannot use __attribute__((constructor)) to register the supported
> > > expressions in runtime when the library is statically linked. This lead
> > > us to some explicit libnftnl_init() function that needs to be called
> > > from the main() function of the client program.
> > 
> > Just wondering, why not? They should still be invoked, right?
> 
> This seems to run when the shared library is loaded. When the build is
> static, that never happens.
> 
> In iptables, we're resolving this with an init_extensions() function
> that is called from main() so these are registered in run-time. I
> would like to skip such explicit call from the client programs.
> 
> If you have any better solution, let me know. I actually liked that
> the expression class, including its registration was self-contained
> :-(.

Yeah, me too. Do you have a pointer to the bug report? I'm surprised
that they are not invoked, from what I can tell that should happen in
any case.

> 
> > > This patch reverts 4dd0772 ("expr: use __attribute__((constructor)) to
> > > register expression").
> > > 
> > > Reported-by: Laurent Bercot <ska-devel@skarnet.org>
> > > Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
> 

Re: [PATCH libnftnl] src: restore static array with expression operations

[Laurent Bercot]

On 23/03/2015 14:08, Patrick McHardy wrote:
> Yeah, me too. Do you have a pointer to the bug report? I'm surprised
> that they are not invoked, from what I can tell that should happen in
> any case.

  Hi Patrick,
  I reported the bug on the netfilter@vger.kernel.org mailing-list
(not the -devel one.)

  I just tested Pablo's proposed patch. It's working perfectly.
  Thanks a lot, Pablo.

-- 
  Laurent

Re: [PATCH libnftnl] src: restore static array with expression operations

[Patrick McHardy]

On 23.03, Laurent Bercot wrote:
> On 23/03/2015 14:08, Patrick McHardy wrote:
> >Yeah, me too. Do you have a pointer to the bug report? I'm surprised
> >that they are not invoked, from what I can tell that should happen in
> >any case.
> 
>  Hi Patrick,
>  I reported the bug on the netfilter@vger.kernel.org mailing-list
> (not the -devel one.)
> 
>  I just tested Pablo's proposed patch. It's working perfectly.

I don't doubt that :) The question is why its not working with
constructors.

Could you please forward your bug report? I'm not subscribed to
netfilter@. Thanks!

Re: [PATCH libnftnl] src: restore static array with expression operations

[Laurent Bercot]

  Here is the first mail I sent to netfilter@.
  The whole thread can be read at
  http://comments.gmane.org/gmane.comp.security.firewalls.netfilter.general/47842

-----
  Hello,

  (Platform: Intel Atom (x86_64), Linux 3.19.1, musl 1.1.7,
latest nftables/libnftnl/libmnl from git. All iptables modules
out of the kernel, all necessary nftables modules in.)

  I can flush tables, create tables and create chains with nft
without trouble; however, every time I try and add a rule to
a chain, no matter what chain, no matter in what table, I get
the following error:

  netlink.c:182: Memory allocation failure

  I dug a bit and found that the error always happens when
alloc_nft_expr() is called for the *first* time (which is also
the last, since nft exits at that point...) and it is always
called with the argument "payload".

  What is happening ? Anything I could do to help fix it ?
  Thanks,

-- 
  Laurent
-----

Re: [PATCH libnftnl] src: restore static array with expression operations

[Patrick McHardy]

On 23.03, Laurent Bercot wrote:
> 
>  Here is the first mail I sent to netfilter@.
>  The whole thread can be read at
>  http://comments.gmane.org/gmane.comp.security.firewalls.netfilter.general/47842


Thanks. Seems the reason is that the linker will discard unused
symbols and from its' perspective the contructors are unused.

I tried experimenting with __attribute__((used)) but it doesn't
help.

What does work is using

-Wl,--whole-archive libnftnl.a -Wl,--no-whole-archive

Not sure if we want to take this path, but it seems acceptable to
me.

Re: [PATCH libnftnl] src: restore static array with expression operations

[Laurent Bercot]

On 23/03/2015 14:54, Patrick McHardy wrote:
> What does work is using
>
> -Wl,--whole-archive libnftnl.a -Wl,--no-whole-archive
>
> Not sure if we want to take this path, but it seems acceptable to
> me.

  I'm sorry, but that is not acceptable to me : it defeats
the purpose of static archives, and forces nft, and every
subsequent program using libnftnl, to include in its binary
every possible optional feature you may want to add to libnftnl.

  As a low-level networking utility, nft has its place on
embedded devices (which is my current case). The statically
linked binary for x86_64 (with musl) is already more than 600 kB,
stripped: that is huge. It's more than my whole busybox binary.
And that is with XML and JSON support entirely disabled.

  Risking further growth in an uncontrollable way just to use a
gcc-specific feature - which also prevents compiling it with
clang/llvm - doesn't sound like the right solution.

  As a user, Pablo's patch looks like a good fix to me.

-- 
  Laurent

Re: [PATCH libnftnl] src: restore static array with expression operations

[Patrick McHardy]

On 23.03, Laurent Bercot wrote:
> On 23/03/2015 14:54, Patrick McHardy wrote:
> >What does work is using
> >
> >-Wl,--whole-archive libnftnl.a -Wl,--no-whole-archive
> >
> >Not sure if we want to take this path, but it seems acceptable to
> >me.
> 
>  I'm sorry, but that is not acceptable to me : it defeats
> the purpose of static archives, and forces nft, and every
> subsequent program using libnftnl, to include in its binary
> every possible optional feature you may want to add to libnftnl.
> 
>  As a low-level networking utility, nft has its place on
> embedded devices (which is my current case). The statically
> linked binary for x86_64 (with musl) is already more than 600 kB,
> stripped: that is huge. It's more than my whole busybox binary.
> And that is with XML and JSON support entirely disabled.

I would be surprised if the alternative provides a much smaller
binary. Basically everything is referenced through the registered
structures and functions called from there. I don't think it
makes any difference.

>  Risking further growth in an uncontrollable way just to use a
> gcc-specific feature - which also prevents compiling it with
> clang/llvm - doesn't sound like the right solution.
> 
>  As a user, Pablo's patch looks like a good fix to me.

Well, we would like to keep the callbacks. We can continue to
look for a different solution. But either way you will have
tons of potentially unused functions in there since the library
resolves a lot of things at runtime.

Re: [PATCH libnftnl] src: restore static array with expression operations

[Laurent Bercot]

On 23/03/2015 15:50, Patrick McHardy wrote:
> I would be surprised if the alternative provides a much smaller
> binary. Basically everything is referenced through the registered
> structures and functions called from there. I don't think it
> makes any difference.

  It's the case for now, but it might not be in the future. Else,
why keep libnftnl as a separate package from nftables?


> Well, we would like to keep the callbacks. We can continue to
> look for a different solution. But either way you will have
> tons of potentially unused functions in there since the library
> resolves a lot of things at runtime.

  I understand that, and don't mind the current 600k that much.
I am opposed to linking with --whole-archive on principle, but
I'll take any other solution that suits you. Any *clean* solution,
I mean. ;)

-- 
  Laurent