netfilter: nf_tables: add inet ingress support

This patch adds a new ingress hook for the inet family. The inet ingress
hook emulates the IP receive path code, therefore, unclean packets are
drop before walking over the ruleset in this basechain.

This patch also introduces the nft_base_chain_netdev() helper function
to check if this hook is bound to one or more devices (through the hook
list infrastructure). This check allows to perform the same handling for
the inet ingress as it would be a netdev ingress chain from the control
plane.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 85 insertions, 0 deletions

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index 0bd2a081ae39..3965ce18226f 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -1081,6 +1081,12 @@ struct nft_table {
 	u8				*udata;
 };
 
+static inline bool nft_base_chain_netdev(int family, u32 hooknum)
+{
+	return family == NFPROTO_NETDEV ||
+	       (family == NFPROTO_INET && hooknum == NF_INET_INGRESS);
+}
+
 void nft_register_chain_type(const struct nft_chain_type *);
 void nft_unregister_chain_type(const struct nft_chain_type *);
 
diff --git a/include/net/netfilter/nf_tables_ipv4.h b/include/net/netfilter/nf_tables_ipv4.h
index ed7b511f0a59..1f7bea39ad1b 100644
--- a/include/net/netfilter/nf_tables_ipv4.h
+++ b/include/net/netfilter/nf_tables_ipv4.h
@@ -53,4 +53,37 @@ static inline void nft_set_pktinfo_ipv4_validate(struct nft_pktinfo *pkt,
 		nft_set_pktinfo_unspec(pkt, skb);
 }
 
+static inline int nft_set_pktinfo_ipv4_ingress(struct nft_pktinfo *pkt,
+					       struct sk_buff *skb)
+{
+	struct iphdr *iph;
+	u32 len, thoff;
+
+	if (!pskb_may_pull(skb, sizeof(*iph)))
+		return -1;
+
+	iph = ip_hdr(skb);
+	if (iph->ihl < 5 || iph->version != 4)
+		goto inhdr_error;
+
+	len = ntohs(iph->tot_len);
+	thoff = iph->ihl * 4;
+	if (skb->len < len) {
+		__IP_INC_STATS(nft_net(pkt), IPSTATS_MIB_INTRUNCATEDPKTS);
+		return -1;
+	} else if (len < thoff) {
+		goto inhdr_error;
+	}
+
+	pkt->tprot_set = true;
+	pkt->tprot = iph->protocol;
+	pkt->xt.thoff = thoff;
+	pkt->xt.fragoff = ntohs(iph->frag_off) & IP_OFFSET;
+
+	return 0;
+
+inhdr_error:
+	__IP_INC_STATS(nft_net(pkt), IPSTATS_MIB_INHDRERRORS);
+	return -1;
+}
 #endif
diff --git a/include/net/netfilter/nf_tables_ipv6.h b/include/net/netfilter/nf_tables_ipv6.h
index d0f1c537b017..867de29f3f7a 100644
--- a/include/net/netfilter/nf_tables_ipv6.h
+++ b/include/net/netfilter/nf_tables_ipv6.h
@@ -70,4 +70,50 @@ static inline void nft_set_pktinfo_ipv6_validate(struct nft_pktinfo *pkt,
 		nft_set_pktinfo_unspec(pkt, skb);
 }
 
+static inline int nft_set_pktinfo_ipv6_ingress(struct nft_pktinfo *pkt,
+					       struct sk_buff *skb)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	unsigned int flags = IP6_FH_F_AUTH;
+	unsigned short frag_off;
+	unsigned int thoff = 0;
+	struct inet6_dev *idev;
+	struct ipv6hdr *ip6h;
+	int protohdr;
+	u32 pkt_len;
+
+	if (!pskb_may_pull(skb, sizeof(*ip6h)))
+		return -1;
+
+	ip6h = ipv6_hdr(skb);
+	if (ip6h->version != 6)
+		goto inhdr_error;
+
+	pkt_len = ntohs(ip6h->payload_len);
+	if (pkt_len + sizeof(*ip6h) > skb->len) {
+		idev = __in6_dev_get(nft_in(pkt));
+		__IP6_INC_STATS(nft_net(pkt), idev, IPSTATS_MIB_INTRUNCATEDPKTS);
+		return -1;
+	}
+
+	protohdr = ipv6_find_hdr(pkt->skb, &thoff, -1, &frag_off, &flags);
+	if (protohdr < 0)
+		goto inhdr_error;
+
+	pkt->tprot_set = true;
+	pkt->tprot = protohdr;
+	pkt->xt.thoff = thoff;
+	pkt->xt.fragoff = frag_off;
+
+	return 0;
+
+inhdr_error:
+	idev = __in6_dev_get(nft_in(pkt));
+	__IP6_INC_STATS(nft_net(pkt), idev, IPSTATS_MIB_INHDRERRORS);
+	return -1;
+#else
+	return -1;
+#endif
+}
+
 #endif