netfilter: nft_redir: use `struct nf_nat_range2` throughout and deduplicate eval call-backs

`nf_nat_redirect_ipv4` takes a `struct nf_nat_ipv4_multi_range_compat`,
but converts it internally to a `struct nf_nat_range2`.  Change the
function to take the latter, factor out the code now shared with
`nf_nat_redirect_ipv6`, move the conversion to the xt_REDIRECT module,
and update the ipv4 range initialization in the nft_redir module.

Replace a bare hex constant for 127.0.0.1 with a macro.

Remove `WARN_ON`.  `nf_nat_setup_info` calls `nf_ct_is_confirmed`:

	/* Can't setup nat info for confirmed ct. */
	if (nf_ct_is_confirmed(ct))
		return NF_ACCEPT;

This means that `ct` cannot be null or the kernel will crash, and
implies that `ctinfo` is `IP_CT_NEW` or `IP_CT_RELATED`.

nft_redir has separate ipv4 and ipv6 call-backs which share much of
their code, and an inet one switch containing a switch that calls one of
the others based on the family of the packet.  Merge the ipv4 and ipv6
ones into the inet one in order to get rid of the duplicate code.

Const-qualify the `priv` pointer since we don't need to write through
it.

Assign `priv->flags` to the range instead of OR-ing it in.

Set the `NF_NAT_RANGE_PROTO_SPECIFIED` flag once during init, rather
than on every eval.
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Florian Westphal <fw@strlen.de>

include/net/netfilter/nf_nat_redirect.h

@@ -6,8 +6,7 @@
 #include <uapi/linux/netfilter/nf_nat.h>
 
 unsigned int
-nf_nat_redirect_ipv4(struct sk_buff *skb,
-		     const struct nf_nat_ipv4_multi_range_compat *mr,
+nf_nat_redirect_ipv4(struct sk_buff *skb, const struct nf_nat_range2 *range,
 		     unsigned int hooknum);
 unsigned int
 nf_nat_redirect_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,

net/netfilter/nf_nat_redirect.c

@@ -10,6 +10,7 @@
 
 #include <linux/if.h>
 #include <linux/inetdevice.h>
+#include <linux/in.h>
 #include <linux/ip.h>
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
@@ -24,54 +25,56 @@
 #include <net/netfilter/nf_nat.h>
 #include <net/netfilter/nf_nat_redirect.h>
 
+static unsigned int
+nf_nat_redirect(struct sk_buff *skb, const struct nf_nat_range2 *range,
+		const union nf_inet_addr *newdst)
+{
+	struct nf_nat_range2 newrange;
+	enum ip_conntrack_info ctinfo;
+	struct nf_conn *ct;
+
+	ct = nf_ct_get(skb, &ctinfo);
+
+	memset(&newrange, 0, sizeof(newrange));
+
+	newrange.flags		= range->flags | NF_NAT_RANGE_MAP_IPS;
+	newrange.min_addr	= *newdst;
+	newrange.max_addr	= *newdst;
+	newrange.min_proto	= range->min_proto;
+	newrange.max_proto	= range->max_proto;
+
+	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
+}
+
 unsigned int
-nf_nat_redirect_ipv4(struct sk_buff *skb,
-		     const struct nf_nat_ipv4_multi_range_compat *mr,
+nf_nat_redirect_ipv4(struct sk_buff *skb, const struct nf_nat_range2 *range,
 		     unsigned int hooknum)
 {
-	struct nf_conn *ct;
-	enum ip_conntrack_info ctinfo;
-	__be32 newdst;
-	struct nf_nat_range2 newrange;
+	union nf_inet_addr newdst = {};
 
 	WARN_ON(hooknum != NF_INET_PRE_ROUTING &&
 		hooknum != NF_INET_LOCAL_OUT);
 
-	ct = nf_ct_get(skb, &ctinfo);
-	WARN_ON(!(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED)));
-
 	/* Local packets: make them go to loopback */
 	if (hooknum == NF_INET_LOCAL_OUT) {
-		newdst = htonl(0x7F000001);
+		newdst.ip = htonl(INADDR_LOOPBACK);
 	} else {
 		const struct in_device *indev;
 
-		newdst = 0;
-
 		indev = __in_dev_get_rcu(skb->dev);
 		if (indev) {
 			const struct in_ifaddr *ifa;
 
 			ifa = rcu_dereference(indev->ifa_list);
 			if (ifa)
-				newdst = ifa->ifa_local;
+				newdst.ip = ifa->ifa_local;
 		}
 
-		if (!newdst)
+		if (!newdst.ip)
 			return NF_DROP;
 	}
 
-	/* Transfer from original range. */
-	memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
-	memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
-	newrange.flags	     = mr->range[0].flags | NF_NAT_RANGE_MAP_IPS;
-	newrange.min_addr.ip = newdst;
-	newrange.max_addr.ip = newdst;
-	newrange.min_proto   = mr->range[0].min;
-	newrange.max_proto   = mr->range[0].max;
-
-	/* Hand modified range to generic setup. */
-	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
+	return nf_nat_redirect(skb, range, &newdst);
 }
 EXPORT_SYMBOL_GPL(nf_nat_redirect_ipv4);
 
@@ -81,14 +84,10 @@ unsigned int
 nf_nat_redirect_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
 		     unsigned int hooknum)
 {
-	struct nf_nat_range2 newrange;
-	struct in6_addr newdst;
-	enum ip_conntrack_info ctinfo;
-	struct nf_conn *ct;
+	union nf_inet_addr newdst = {};
 
-	ct = nf_ct_get(skb, &ctinfo);
 	if (hooknum == NF_INET_LOCAL_OUT) {
-		newdst = loopback_addr;
+		newdst.in6 = loopback_addr;
 	} else {
 		struct inet6_dev *idev;
 		struct inet6_ifaddr *ifa;
@@ -98,7 +97,7 @@ nf_nat_redirect_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
 		if (idev != NULL) {
 			read_lock_bh(&idev->lock);
 			list_for_each_entry(ifa, &idev->addr_list, if_list) {
-				newdst = ifa->addr;
+				newdst.in6 = ifa->addr;
 				addr = true;
 				break;
 			}
@@ -109,12 +108,6 @@ nf_nat_redirect_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
 			return NF_DROP;
 	}
 
-	newrange.flags		= range->flags | NF_NAT_RANGE_MAP_IPS;
-	newrange.min_addr.in6	= newdst;
-	newrange.max_addr.in6	= newdst;
-	newrange.min_proto	= range->min_proto;
-	newrange.max_proto	= range->max_proto;
-
-	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
+	return nf_nat_redirect(skb, range, &newdst);
 }
 EXPORT_SYMBOL_GPL(nf_nat_redirect_ipv6);

net/netfilter/nft_redir.c

@@ -64,6 +64,8 @@ static int nft_redir_init(const struct nft_ctx *ctx,
 		} else {
 			priv->sreg_proto_max = priv->sreg_proto_min;
 		}
+
+		priv->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
 	}
 
 	if (tb[NFTA_REDIR_FLAGS]) {
@@ -99,25 +101,37 @@ static int nft_redir_dump(struct sk_buff *skb,
 	return -1;
 }
 
-static void nft_redir_ipv4_eval(const struct nft_expr *expr,
-				struct nft_regs *regs,
-				const struct nft_pktinfo *pkt)
+static void nft_redir_eval(const struct nft_expr *expr,
+			   struct nft_regs *regs,
+			   const struct nft_pktinfo *pkt)
 {
-	struct nft_redir *priv = nft_expr_priv(expr);
-	struct nf_nat_ipv4_multi_range_compat mr;
+	const struct nft_redir *priv = nft_expr_priv(expr);
+	struct nf_nat_range2 range;
 
-	memset(&mr, 0, sizeof(mr));
+	memset(&range, 0, sizeof(range));
+	range.flags = priv->flags;
 	if (priv->sreg_proto_min) {
-		mr.range[0].min.all = (__force __be16)nft_reg_load16(
-			&regs->data[priv->sreg_proto_min]);
-		mr.range[0].max.all = (__force __be16)nft_reg_load16(
-			&regs->data[priv->sreg_proto_max]);
-		mr.range[0].flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
+		range.min_proto.all = (__force __be16)
+			nft_reg_load16(&regs->data[priv->sreg_proto_min]);
+		range.max_proto.all = (__force __be16)
+			nft_reg_load16(&regs->data[priv->sreg_proto_max]);
 	}
 
-	mr.range[0].flags |= priv->flags;
-
-	regs->verdict.code = nf_nat_redirect_ipv4(pkt->skb, &mr, nft_hook(pkt));
+	switch (nft_pf(pkt)) {
+	case NFPROTO_IPV4:
+		regs->verdict.code = nf_nat_redirect_ipv4(pkt->skb, &range,
+							  nft_hook(pkt));
+		break;
+#ifdef CONFIG_NF_TABLES_IPV6
+	case NFPROTO_IPV6:
+		regs->verdict.code = nf_nat_redirect_ipv6(pkt->skb, &range,
+							  nft_hook(pkt));
+		break;
+#endif
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
 }
 
 static void
@@ -130,7 +144,7 @@ static struct nft_expr_type nft_redir_ipv4_type;
 static const struct nft_expr_ops nft_redir_ipv4_ops = {
 	.type		= &nft_redir_ipv4_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_redir)),
-	.eval		= nft_redir_ipv4_eval,
+	.eval		= nft_redir_eval,
 	.init		= nft_redir_init,
 	.destroy	= nft_redir_ipv4_destroy,
 	.dump		= nft_redir_dump,
@@ -148,28 +162,6 @@ static struct nft_expr_type nft_redir_ipv4_type __read_mostly = {
 };
 
 #ifdef CONFIG_NF_TABLES_IPV6
-static void nft_redir_ipv6_eval(const struct nft_expr *expr,
-				struct nft_regs *regs,
-				const struct nft_pktinfo *pkt)
-{
-	struct nft_redir *priv = nft_expr_priv(expr);
-	struct nf_nat_range2 range;
-
-	memset(&range, 0, sizeof(range));
-	if (priv->sreg_proto_min) {
-		range.min_proto.all = (__force __be16)nft_reg_load16(
-			&regs->data[priv->sreg_proto_min]);
-		range.max_proto.all = (__force __be16)nft_reg_load16(
-			&regs->data[priv->sreg_proto_max]);
-		range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
-	}
-
-	range.flags |= priv->flags;
-
-	regs->verdict.code =
-		nf_nat_redirect_ipv6(pkt->skb, &range, nft_hook(pkt));
-}
-
 static void
 nft_redir_ipv6_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
 {
@@ -180,7 +172,7 @@ static struct nft_expr_type nft_redir_ipv6_type;
 static const struct nft_expr_ops nft_redir_ipv6_ops = {
 	.type		= &nft_redir_ipv6_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_redir)),
-	.eval		= nft_redir_ipv6_eval,
+	.eval		= nft_redir_eval,
 	.init		= nft_redir_init,
 	.destroy	= nft_redir_ipv6_destroy,
 	.dump		= nft_redir_dump,
@@ -199,20 +191,6 @@ static struct nft_expr_type nft_redir_ipv6_type __read_mostly = {
 #endif
 
 #ifdef CONFIG_NF_TABLES_INET
-static void nft_redir_inet_eval(const struct nft_expr *expr,
-				struct nft_regs *regs,
-				const struct nft_pktinfo *pkt)
-{
-	switch (nft_pf(pkt)) {
-	case NFPROTO_IPV4:
-		return nft_redir_ipv4_eval(expr, regs, pkt);
-	case NFPROTO_IPV6:
-		return nft_redir_ipv6_eval(expr, regs, pkt);
-	}
-
-	WARN_ON_ONCE(1);
-}
-
 static void
 nft_redir_inet_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
 {
@@ -223,7 +201,7 @@ static struct nft_expr_type nft_redir_inet_type;
 static const struct nft_expr_ops nft_redir_inet_ops = {
 	.type		= &nft_redir_inet_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_redir)),
-	.eval		= nft_redir_inet_eval,
+	.eval		= nft_redir_eval,
 	.init		= nft_redir_init,
 	.destroy	= nft_redir_inet_destroy,
 	.dump		= nft_redir_dump,

net/netfilter/xt_REDIRECT.c

@@ -46,7 +46,6 @@ static void redirect_tg_destroy(const struct xt_tgdtor_param *par)
 	nf_ct_netns_put(par->net, par->family);
 }
 
-/* FIXME: Take multiple ranges --RR */
 static int redirect_tg4_check(const struct xt_tgchk_param *par)
 {
 	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
@@ -65,7 +64,14 @@ static int redirect_tg4_check(const struct xt_tgchk_param *par)
 static unsigned int
 redirect_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 {
-	return nf_nat_redirect_ipv4(skb, par->targinfo, xt_hooknum(par));
+	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
+	struct nf_nat_range2 range = {
+		.flags       = mr->range[0].flags,
+		.min_proto   = mr->range[0].min,
+		.max_proto   = mr->range[0].max,
+	};
+
+	return nf_nat_redirect_ipv4(skb, &range, xt_hooknum(par));
 }
 
 static struct xt_target redirect_tg_reg[] __read_mostly = {