extensions: *NAT: Drop NF_NAT_RANGE_PROTO_RANDOM* flag checks

SNAT, DNAT and REDIRECT extensions tried to prevent
NF_NAT_RANGE_PROTO_RANDOM flag from being set if no port or address was
also given.

With SNAT and DNAT, this is not possible as the respective
--to-destination or --to-source parameters are mandatory anyway.

Looking at the kernel code, doing so with REDIRECT seems harmless.
Moreover, nftables supports 'redirect random' without specifying a
port-range.

Signed-off-by: Phil Sutter <phil@nwl.cc>

5 files changed, 19 insertions, 49 deletions

diff --git a/extensions/libip6t_SNAT.c b/extensions/libip6t_SNAT.c
index 4fe272b2..8bf7b035 100644
--- a/extensions/libip6t_SNAT.c
+++ b/extensions/libip6t_SNAT.c
@@ -20,9 +20,6 @@ enum {
 	O_RANDOM,
 	O_RANDOM_FULLY,
 	O_PERSISTENT,
-	F_TO_SRC       = 1 << O_TO_SRC,
-	F_RANDOM       = 1 << O_RANDOM,
-	F_RANDOM_FULLY = 1 << O_RANDOM_FULLY,
 };
 
 static void SNAT_help(void)
@@ -166,19 +163,13 @@ static void SNAT_parse(struct xt_option_call *cb)
 	case O_PERSISTENT:
 		range->flags |= NF_NAT_RANGE_PERSISTENT;
 		break;
-	}
-}
-
-static void SNAT_fcheck(struct xt_fcheck_call *cb)
-{
-	static const unsigned int f = F_TO_SRC | F_RANDOM;
-	static const unsigned int r = F_TO_SRC | F_RANDOM_FULLY;
-	struct nf_nat_range *range = cb->data;
-
-	if ((cb->xflags & f) == f)
+	case O_RANDOM:
 		range->flags |= NF_NAT_RANGE_PROTO_RANDOM;
-	if ((cb->xflags & r) == r)
+		break;
+	case O_RANDOM_FULLY:
 		range->flags |= NF_NAT_RANGE_PROTO_RANDOM_FULLY;
+		break;
+	}
 }
 
 static void print_range(const struct nf_nat_range *range)
@@ -295,7 +286,6 @@ static struct xtables_target snat_tg_reg = {
 	.userspacesize	= XT_ALIGN(sizeof(struct nf_nat_range)),
 	.help		= SNAT_help,
 	.x6_parse	= SNAT_parse,
-	.x6_fcheck	= SNAT_fcheck,
 	.print		= SNAT_print,
 	.save		= SNAT_save,
 	.x6_options	= SNAT_opts,
diff --git a/extensions/libipt_SNAT.c b/extensions/libipt_SNAT.c
index 211a20bc..9c8cdb46 100644
--- a/extensions/libipt_SNAT.c
+++ b/extensions/libipt_SNAT.c
@@ -13,9 +13,6 @@ enum {
 	O_RANDOM,
 	O_RANDOM_FULLY,
 	O_PERSISTENT,
-	F_TO_SRC       = 1 << O_TO_SRC,
-	F_RANDOM       = 1 << O_RANDOM,
-	F_RANDOM_FULLY = 1 << O_RANDOM_FULLY,
 };
 
 static void SNAT_help(void)
@@ -141,20 +138,19 @@ static void SNAT_parse(struct xt_option_call *cb)
 	case O_PERSISTENT:
 		mr->range->flags |= NF_NAT_RANGE_PERSISTENT;
 		break;
+	case O_RANDOM:
+		mr->range->flags |= NF_NAT_RANGE_PROTO_RANDOM;
+		break;
+	case O_RANDOM_FULLY:
+		mr->range->flags |= NF_NAT_RANGE_PROTO_RANDOM_FULLY;
+		break;
 	}
 }
 
 static void SNAT_fcheck(struct xt_fcheck_call *cb)
 {
-	static const unsigned int f = F_TO_SRC | F_RANDOM;
-	static const unsigned int r = F_TO_SRC | F_RANDOM_FULLY;
 	struct nf_nat_ipv4_multi_range_compat *mr = cb->data;
 
-	if ((cb->xflags & f) == f)
-		mr->range->flags |= NF_NAT_RANGE_PROTO_RANDOM;
-	if ((cb->xflags & r) == r)
-		mr->range->flags |= NF_NAT_RANGE_PROTO_RANDOM_FULLY;
-
 	mr->rangesize = 1;
 }
 
diff --git a/extensions/libxt_DNAT.c b/extensions/libxt_DNAT.c
index 7bfefc79..af445187 100644
--- a/extensions/libxt_DNAT.c
+++ b/extensions/libxt_DNAT.c
@@ -31,9 +31,6 @@ enum {
 	O_TO_PORTS,
 	O_RANDOM,
 	O_PERSISTENT,
-	F_TO_DEST  = 1 << O_TO_DEST,
-	F_TO_PORTS = 1 << O_TO_PORTS,
-	F_RANDOM   = 1 << O_RANDOM,
 };
 
 static void DNAT_help(void)
@@ -229,6 +226,9 @@ static void __DNAT_parse(struct xt_option_call *cb, __u16 proto,
 	case O_PERSISTENT:
 		range->flags |= NF_NAT_RANGE_PERSISTENT;
 		break;
+	case O_RANDOM:
+		range->flags |= NF_NAT_RANGE_PROTO_RANDOM;
+		break;
 	}
 }
 
@@ -250,21 +250,12 @@ static void DNAT_parse(struct xt_option_call *cb)
 		mr->range->max = range.max_proto;
 		/* fall through */
 	case O_PERSISTENT:
+	case O_RANDOM:
 		mr->range->flags |= range.flags;
 		break;
 	}
 }
 
-static void __DNAT_fcheck(struct xt_fcheck_call *cb, unsigned int *flags)
-{
-	static const unsigned int redir_f = F_TO_PORTS | F_RANDOM;
-	static const unsigned int dnat_f = F_TO_DEST | F_RANDOM;
-
-	if ((cb->xflags & redir_f) == redir_f ||
-	    (cb->xflags & dnat_f) == dnat_f)
-		*flags |= NF_NAT_RANGE_PROTO_RANDOM;
-}
-
 static void DNAT_fcheck(struct xt_fcheck_call *cb)
 {
 	struct nf_nat_ipv4_multi_range_compat *mr = cb->data;
@@ -274,8 +265,6 @@ static void DNAT_fcheck(struct xt_fcheck_call *cb)
 	if (mr->range[0].flags & NF_NAT_RANGE_PROTO_OFFSET)
 		xtables_error(PARAMETER_PROBLEM,
 			      "Shifted portmap ranges not supported with this kernel");
-
-	__DNAT_fcheck(cb, &mr->range[0].flags);
 }
 
 static char *sprint_range(const struct nf_nat_range2 *r, int family)
@@ -388,11 +377,6 @@ static void DNAT_parse_v2(struct xt_option_call *cb)
 	__DNAT_parse(cb, entry->ip.proto, cb->data, AF_INET);
 }
 
-static void DNAT_fcheck_v2(struct xt_fcheck_call *cb)
-{
-	__DNAT_fcheck(cb, &((struct nf_nat_range2 *)cb->data)->flags);
-}
-
 static void DNAT_print_v2(const void *ip, const struct xt_entry_target *target,
                        int numeric)
 {
@@ -428,8 +412,6 @@ static void DNAT_fcheck6(struct xt_fcheck_call *cb)
 	if (range->flags & NF_NAT_RANGE_PROTO_OFFSET)
 		xtables_error(PARAMETER_PROBLEM,
 			      "Shifted portmap ranges not supported with this kernel");
-
-	__DNAT_fcheck(cb, &range->flags);
 }
 
 static void DNAT_print6(const void *ip, const struct xt_entry_target *target,
@@ -619,7 +601,6 @@ static struct xtables_target dnat_tg_reg[] = {
 		.print		= DNAT_print_v2,
 		.save		= DNAT_save_v2,
 		.x6_parse	= DNAT_parse_v2,
-		.x6_fcheck	= DNAT_fcheck_v2,
 		.x6_options	= DNAT_opts,
 		.xlate		= DNAT_xlate_v2,
 	},
@@ -634,7 +615,6 @@ static struct xtables_target dnat_tg_reg[] = {
 		.print		= DNAT_print6_v2,
 		.save		= DNAT_save6_v2,
 		.x6_parse	= DNAT_parse6_v2,
-		.x6_fcheck	= DNAT_fcheck_v2,
 		.x6_options	= DNAT_opts,
 		.xlate		= DNAT_xlate6_v2,
 	},
diff --git a/extensions/libxt_REDIRECT.t b/extensions/libxt_REDIRECT.t
index f607dd0a..362efa84 100644
--- a/extensions/libxt_REDIRECT.t
+++ b/extensions/libxt_REDIRECT.t
@@ -14,3 +14,4 @@
 -p tcp -j REDIRECT --to-ports ftp-ssh;;FAIL
 -p tcp -j REDIRECT --to-ports 10-ssh;;FAIL
 -j REDIRECT --to-ports 42;;FAIL
+-j REDIRECT --random;=;OK
diff --git a/extensions/libxt_REDIRECT.txlate b/extensions/libxt_REDIRECT.txlate
index 2c536495..36419a46 100644
--- a/extensions/libxt_REDIRECT.txlate
+++ b/extensions/libxt_REDIRECT.txlate
@@ -16,6 +16,9 @@ nft add rule ip nat prerouting tcp dport 80 counter redirect to :10-22
 iptables-translate -t nat -A prerouting -p tcp --dport 80 -j REDIRECT --to-ports 8080 --random
 nft add rule ip nat prerouting tcp dport 80 counter redirect to :8080 random
 
+iptables-translate -t nat -A prerouting -j REDIRECT --random
+nft add rule ip nat prerouting counter redirect random
+
 ip6tables-translate -t nat -A prerouting -p tcp --dport 80 -j REDIRECT
 nft add rule ip6 nat prerouting tcp dport 80 counter redirect