act_ct: Support GRE offload

Support GREv0 without NAT.
Signed-off-by: NToshiaki Makita <toshiaki.makita1@gmail.com>
Acked-by: NPaul Blakey <paulb@nvidia.com>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/sched/act_ct.c

@@ -415,6 +415,19 @@ static void tcf_ct_flow_table_process_conn(struct tcf_ct_flow_table *ct_ft,
 		break;
 	case IPPROTO_UDP:
 		break;
+#ifdef CONFIG_NF_CT_PROTO_GRE
+	case IPPROTO_GRE: {
+		struct nf_conntrack_tuple *tuple;
+
+		if (ct->status & IPS_NAT_MASK)
+			return;
+		tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
+		/* No support for GRE v1 */
+		if (tuple->src.u.gre.key || tuple->dst.u.gre.key)
+			return;
+		break;
+	}
+#endif
 	default:
 		return;
 	}
@@ -434,6 +447,8 @@ tcf_ct_flow_table_fill_tuple_ipv4(struct sk_buff *skb,
 	struct flow_ports *ports;
 	unsigned int thoff;
 	struct iphdr *iph;
+	size_t hdrsize;
+	u8 ipproto;
 
 	if (!pskb_network_may_pull(skb, sizeof(*iph)))
 		return false;
@@ -445,29 +460,54 @@ tcf_ct_flow_table_fill_tuple_ipv4(struct sk_buff *skb,
 	    unlikely(thoff != sizeof(struct iphdr)))
 		return false;
 
-	if (iph->protocol != IPPROTO_TCP &&
-	    iph->protocol != IPPROTO_UDP)
+	ipproto = iph->protocol;
+	switch (ipproto) {
+	case IPPROTO_TCP:
+		hdrsize = sizeof(struct tcphdr);
+		break;
+	case IPPROTO_UDP:
+		hdrsize = sizeof(*ports);
+		break;
+#ifdef CONFIG_NF_CT_PROTO_GRE
+	case IPPROTO_GRE:
+		hdrsize = sizeof(struct gre_base_hdr);
+		break;
+#endif
+	default:
 		return false;
+	}
 
 	if (iph->ttl <= 1)
 		return false;
 
-	if (!pskb_network_may_pull(skb, iph->protocol == IPPROTO_TCP ?
-					thoff + sizeof(struct tcphdr) :
-					thoff + sizeof(*ports)))
+	if (!pskb_network_may_pull(skb, thoff + hdrsize))
 		return false;
 
-	iph = ip_hdr(skb);
-	if (iph->protocol == IPPROTO_TCP)
+	switch (ipproto) {
+	case IPPROTO_TCP:
 		*tcph = (void *)(skb_network_header(skb) + thoff);
+		fallthrough;
+	case IPPROTO_UDP:
+		ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
+		tuple->src_port = ports->source;
+		tuple->dst_port = ports->dest;
+		break;
+	case IPPROTO_GRE: {
+		struct gre_base_hdr *greh;
+
+		greh = (struct gre_base_hdr *)(skb_network_header(skb) + thoff);
+		if ((greh->flags & GRE_VERSION) != GRE_VERSION_0)
+			return false;
+		break;
+	}
+	}
+
+	iph = ip_hdr(skb);
 
-	ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 	tuple->src_v4.s_addr = iph->saddr;
 	tuple->dst_v4.s_addr = iph->daddr;
-	tuple->src_port = ports->source;
-	tuple->dst_port = ports->dest;
 	tuple->l3proto = AF_INET;
-	tuple->l4proto = iph->protocol;
+	tuple->l4proto = ipproto;
 
 	return true;
 }
@@ -480,36 +520,63 @@ tcf_ct_flow_table_fill_tuple_ipv6(struct sk_buff *skb,
 	struct flow_ports *ports;
 	struct ipv6hdr *ip6h;
 	unsigned int thoff;
+	size_t hdrsize;
+	u8 nexthdr;
 
 	if (!pskb_network_may_pull(skb, sizeof(*ip6h)))
 		return false;
 
 	ip6h = ipv6_hdr(skb);
+	thoff = sizeof(*ip6h);
 
-	if (ip6h->nexthdr != IPPROTO_TCP &&
-	    ip6h->nexthdr != IPPROTO_UDP)
-		return false;
+	nexthdr = ip6h->nexthdr;
+	switch (nexthdr) {
+	case IPPROTO_TCP:
+		hdrsize = sizeof(struct tcphdr);
+		break;
+	case IPPROTO_UDP:
+		hdrsize = sizeof(*ports);
+		break;
+#ifdef CONFIG_NF_CT_PROTO_GRE
+	case IPPROTO_GRE:
+		hdrsize = sizeof(struct gre_base_hdr);
+		break;
+#endif
+	default:
+		return -1;
+	}
 
 	if (ip6h->hop_limit <= 1)
 		return false;
 
-	thoff = sizeof(*ip6h);
-	if (!pskb_network_may_pull(skb, ip6h->nexthdr == IPPROTO_TCP ?
-					thoff + sizeof(struct tcphdr) :
-					thoff + sizeof(*ports)))
+	if (!pskb_network_may_pull(skb, thoff + hdrsize))
 		return false;
 
-	ip6h = ipv6_hdr(skb);
-	if (ip6h->nexthdr == IPPROTO_TCP)
+	switch (nexthdr) {
+	case IPPROTO_TCP:
 		*tcph = (void *)(skb_network_header(skb) + thoff);
+		fallthrough;
+	case IPPROTO_UDP:
+		ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
+		tuple->src_port = ports->source;
+		tuple->dst_port = ports->dest;
+		break;
+	case IPPROTO_GRE: {
+		struct gre_base_hdr *greh;
+
+		greh = (struct gre_base_hdr *)(skb_network_header(skb) + thoff);
+		if ((greh->flags & GRE_VERSION) != GRE_VERSION_0)
+			return false;
+		break;
+	}
+	}
+
+	ip6h = ipv6_hdr(skb);
 
-	ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 	tuple->src_v6 = ip6h->saddr;
 	tuple->dst_v6 = ip6h->daddr;
-	tuple->src_port = ports->source;
-	tuple->dst_port = ports->dest;
 	tuple->l3proto = AF_INET6;
-	tuple->l4proto = ip6h->nexthdr;
+	tuple->l4proto = nexthdr;
 
 	return true;
 }