netfilter: nft_reject_inet: allow to use reject from inet ingress

Enhance validation to support for reject from inet ingress chains.

Note that, reject from inet ingress and netdev ingress differ.

Reject packets from inet ingress are sent through ip_local_out() since
inet reject emulates the IP layer receive path. So the reject packet
follows to classic IP output and postrouting paths.

The reject action from netdev ingress assumes the packet not yet entered
the IP layer, so the reject packet is sent through dev_queue_xmit().
Therefore, reject packets from netdev ingress do not follow the classic
IP output and postrouting paths.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/nf_reject_ipv4.c

@@ -246,7 +246,8 @@ void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook)
 	if (!oth)
 		return;
 
-	if (hook == NF_INET_PRE_ROUTING && nf_reject_fill_skb_dst(oldskb))
+	if ((hook == NF_INET_PRE_ROUTING || hook == NF_INET_INGRESS) &&
+	    nf_reject_fill_skb_dst(oldskb) < 0)
 		return;
 
 	if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
@@ -315,7 +316,8 @@ void nf_send_unreach(struct sk_buff *skb_in, int code, int hook)
 	if (iph->frag_off & htons(IP_OFFSET))
 		return;
 
-	if (hook == NF_INET_PRE_ROUTING && nf_reject_fill_skb_dst(skb_in))
+	if ((hook == NF_INET_PRE_ROUTING || hook == NF_INET_INGRESS) &&
+	    nf_reject_fill_skb_dst(skb_in) < 0)
 		return;
 
 	if (skb_csum_unnecessary(skb_in) || !nf_reject_verify_csum(proto)) {

net/ipv6/netfilter/nf_reject_ipv6.c

@@ -304,7 +304,7 @@ void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook)
 	fl6.fl6_sport = otcph->dest;
 	fl6.fl6_dport = otcph->source;
 
-	if (hook == NF_INET_PRE_ROUTING) {
+	if (hook == NF_INET_PRE_ROUTING || hook == NF_INET_INGRESS) {
 		nf_ip6_route(net, &dst, flowi6_to_flowi(&fl6), false);
 		if (!dst)
 			return;
@@ -402,7 +402,8 @@ void nf_send_unreach6(struct net *net, struct sk_buff *skb_in,
 	if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
 		skb_in->dev = net->loopback_dev;
 
-	if (hooknum == NF_INET_PRE_ROUTING && nf_reject6_fill_skb_dst(skb_in))
+	if ((hooknum == NF_INET_PRE_ROUTING || hooknum == NF_INET_INGRESS) &&
+	    nf_reject6_fill_skb_dst(skb_in) < 0)
 		return;
 
 	icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);

net/netfilter/nft_reject_inet.c

@@ -58,6 +58,18 @@ static void nft_reject_inet_eval(const struct nft_expr *expr,
 	regs->verdict.code = NF_DROP;
 }
 
+static int nft_reject_inet_validate(const struct nft_ctx *ctx,
+				    const struct nft_expr *expr,
+				    const struct nft_data **data)
+{
+	return nft_chain_validate_hooks(ctx->chain,
+					(1 << NF_INET_LOCAL_IN) |
+					(1 << NF_INET_FORWARD) |
+					(1 << NF_INET_LOCAL_OUT) |
+					(1 << NF_INET_PRE_ROUTING) |
+					(1 << NF_INET_INGRESS));
+}
+
 static struct nft_expr_type nft_reject_inet_type;
 static const struct nft_expr_ops nft_reject_inet_ops = {
 	.type		= &nft_reject_inet_type,
@@ -65,7 +77,7 @@ static const struct nft_expr_ops nft_reject_inet_ops = {
 	.eval		= nft_reject_inet_eval,
 	.init		= nft_reject_init,
 	.dump		= nft_reject_dump,
-	.validate	= nft_reject_validate,
+	.validate	= nft_reject_inet_validate,
 };
 
 static struct nft_expr_type nft_reject_inet_type __read_mostly = {