From b7556207b12decbe4e79bf218ec5bff073a04ad2 Mon Sep 17 00:00:00 2001
From: Phil Sutter <phil@nwl.cc>
Date: Tue, 27 Nov 2018 20:07:11 +0100
Subject: [PATCH] xtables: Don't use native nftables comments

The problem with converting libxt_comment into nftables comment is that
rules change when parsing from kernel due to comment match being moved
to the end of the match list. And since match ordering matters, the rule
may not be found anymore when checking or deleting. Apart from that,
iptables-nft didn't support multiple comments per rule anymore. This is
a compatibility issue without technical reason.

Leave conversion from nftables comment to libxt_comment in place so we
don't break running systems during an update.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
(cherry picked from commit ccf154d7420c07b6e6febc1c3b8b31d2bd1adbe6)
Signed-off-by: Phil Sutter <psutter@redhat.com>
---
 extensions/libxt_comment.t |  2 ++
 iptables/nft-ipv4.c        | 14 +++-----------
 iptables/nft-ipv6.c        | 14 +++-----------
 iptables/nft.c             | 27 ---------------------------
 iptables/nft.h             |  1 -
 5 files changed, 8 insertions(+), 50 deletions(-)

diff --git a/extensions/libxt_comment.t b/extensions/libxt_comment.t
index f12cd66841e7f..f0c8fb999401b 100644
--- a/extensions/libxt_comment.t
+++ b/extensions/libxt_comment.t
@@ -1,6 +1,8 @@
 :INPUT,FORWARD,OUTPUT
 -m comment;;FAIL
 -m comment --comment;;FAIL
+-p tcp -m tcp --dport 22 -m comment --comment foo;=;OK
+-p tcp -m comment --comment foo -m tcp --dport 22;=;OK
 #
 # it fails with 256 characters
 #
diff --git a/iptables/nft-ipv4.c b/iptables/nft-ipv4.c
index ffb439b4a1128..4497eb9b9347c 100644
--- a/iptables/nft-ipv4.c
+++ b/iptables/nft-ipv4.c
@@ -77,17 +77,9 @@ static int nft_ipv4_add(struct nftnl_rule *r, void *data)
 	add_compat(r, cs->fw.ip.proto, cs->fw.ip.invflags & XT_INV_PROTO);
 
 	for (matchp = cs->matches; matchp; matchp = matchp->next) {
-		/* Use nft built-in comments support instead of comment match */
-		if (strcmp(matchp->match->name, "comment") == 0) {
-			ret = add_comment(r, (char *)matchp->match->m->data);
-			if (ret < 0)
-				goto try_match;
-		} else {
-try_match:
-			ret = add_match(r, matchp->match->m);
-			if (ret < 0)
-				return ret;
-		}
+		ret = add_match(r, matchp->match->m);
+		if (ret < 0)
+			return ret;
 	}
 
 	/* Counters need to me added before the target, otherwise they are
diff --git a/iptables/nft-ipv6.c b/iptables/nft-ipv6.c
index 7bacee4ab3a21..cacb1c9e141f2 100644
--- a/iptables/nft-ipv6.c
+++ b/iptables/nft-ipv6.c
@@ -66,17 +66,9 @@ static int nft_ipv6_add(struct nftnl_rule *r, void *data)
 	add_compat(r, cs->fw6.ipv6.proto, cs->fw6.ipv6.invflags & XT_INV_PROTO);
 
 	for (matchp = cs->matches; matchp; matchp = matchp->next) {
-		/* Use nft built-in comments support instead of comment match */
-		if (strcmp(matchp->match->name, "comment") == 0) {
-			ret = add_comment(r, (char *)matchp->match->m->data);
-			if (ret < 0)
-				goto try_match;
-		} else {
-try_match:
-			ret = add_match(r, matchp->match->m);
-			if (ret < 0)
-				return ret;
-		}
+		ret = add_match(r, matchp->match->m);
+		if (ret < 0)
+			return ret;
 	}
 
 	/* Counters need to me added before the target, otherwise they are
diff --git a/iptables/nft.c b/iptables/nft.c
index e8538d38e0109..6863d851e44c2 100644
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -1107,33 +1107,6 @@ enum udata_type {
 };
 #define UDATA_TYPE_MAX (__UDATA_TYPE_MAX - 1)
 
-int add_comment(struct nftnl_rule *r, const char *comment)
-{
-	struct nftnl_udata_buf *udata;
-	uint32_t len;
-
-	if (nftnl_rule_get_data(r, NFTNL_RULE_USERDATA, &len))
-		return -EALREADY;
-
-	udata = nftnl_udata_buf_alloc(NFT_USERDATA_MAXLEN);
-	if (!udata)
-		return -ENOMEM;
-
-	if (strnlen(comment, 255) == 255)
-		return -ENOSPC;
-
-	if (!nftnl_udata_put_strz(udata, UDATA_TYPE_COMMENT, comment))
-		return -ENOMEM;
-
-	nftnl_rule_set_data(r, NFTNL_RULE_USERDATA,
-			    nftnl_udata_buf_data(udata),
-			    nftnl_udata_buf_len(udata));
-
-	nftnl_udata_buf_free(udata);
-
-	return 0;
-}
-
 static int parse_udata_cb(const struct nftnl_udata *attr, void *data)
 {
 	unsigned char *value = nftnl_udata_get(attr);
diff --git a/iptables/nft.h b/iptables/nft.h
index 9b4ba5f9a63eb..052105fc6f3cd 100644
--- a/iptables/nft.h
+++ b/iptables/nft.h
@@ -116,7 +116,6 @@ int add_match(struct nftnl_rule *r, struct xt_entry_match *m);
 int add_target(struct nftnl_rule *r, struct xt_entry_target *t);
 int add_jumpto(struct nftnl_rule *r, const char *name, int verdict);
 int add_action(struct nftnl_rule *r, struct iptables_command_state *cs, bool goto_set);
-int add_comment(struct nftnl_rule *r, const char *comment);
 char *get_comment(const void *data, uint32_t data_len);
 
 enum nft_rule_print {
-- 
2.21.0