netfilter: flowtable: split IPv6 datapath in helper functions

Add context structure and helper functions to look up for a matching
IPv6 entry in the flowtable and to forward packets.

No functional changes are intended.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>

net/netfilter/nf_flow_table_ip.c

@@ -570,32 +570,31 @@ static void nf_flow_nat_ipv6(const struct flow_offload *flow,
 	}
 }
 
-static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
-			      struct flow_offload_tuple *tuple, u32 *hdrsize,
-			      u32 offset)
+static int nf_flow_tuple_ipv6(struct nf_flowtable_ctx *ctx, struct sk_buff *skb,
+			      struct flow_offload_tuple *tuple)
 {
 	struct flow_ports *ports;
 	struct ipv6hdr *ip6h;
 	unsigned int thoff;
 	u8 nexthdr;
 
-	thoff = sizeof(*ip6h) + offset;
+	thoff = sizeof(*ip6h) + ctx->offset;
 	if (!pskb_may_pull(skb, thoff))
 		return -1;
 
-	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + offset);
+	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + ctx->offset);
 
 	nexthdr = ip6h->nexthdr;
 	switch (nexthdr) {
 	case IPPROTO_TCP:
-		*hdrsize = sizeof(struct tcphdr);
+		ctx->hdrsize = sizeof(struct tcphdr);
 		break;
 	case IPPROTO_UDP:
-		*hdrsize = sizeof(struct udphdr);
+		ctx->hdrsize = sizeof(struct udphdr);
 		break;
 #ifdef CONFIG_NF_CT_PROTO_GRE
 	case IPPROTO_GRE:
-		*hdrsize = sizeof(struct gre_base_hdr);
+		ctx->hdrsize = sizeof(struct gre_base_hdr);
 		break;
 #endif
 	default:
@@ -605,7 +604,7 @@ static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
 	if (ip6h->hop_limit <= 1)
 		return -1;
 
-	if (!pskb_may_pull(skb, thoff + *hdrsize))
+	if (!pskb_may_pull(skb, thoff + ctx->hdrsize))
 		return -1;
 
 	switch (nexthdr) {
@@ -625,65 +624,47 @@ static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
 	}
 	}
 
-	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + offset);
+	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + ctx->offset);
 
 	tuple->src_v6		= ip6h->saddr;
 	tuple->dst_v6		= ip6h->daddr;
 	tuple->l3proto		= AF_INET6;
 	tuple->l4proto		= nexthdr;
-	tuple->iifidx		= dev->ifindex;
+	tuple->iifidx		= ctx->in->ifindex;
 	nf_flow_tuple_encap(skb, tuple);
 
 	return 0;
 }
 
-unsigned int
-nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
-			  const struct nf_hook_state *state)
+static int nf_flow_offload_ipv6_forward(struct nf_flowtable_ctx *ctx,
+					struct nf_flowtable *flow_table,
+					struct flow_offload_tuple_rhash *tuplehash,
+					struct sk_buff *skb)
 {
-	struct flow_offload_tuple_rhash *tuplehash;
-	struct nf_flowtable *flow_table = priv;
-	struct flow_offload_tuple tuple = {};
 	enum flow_offload_tuple_dir dir;
-	const struct in6_addr *nexthop;
 	struct flow_offload *flow;
-	struct net_device *outdev;
 	unsigned int thoff, mtu;
-	u32 hdrsize, offset = 0;
 	struct ipv6hdr *ip6h;
-	struct rt6_info *rt;
-	int ret;
-
-	if (skb->protocol != htons(ETH_P_IPV6) &&
-	    !nf_flow_skb_encap_protocol(skb, htons(ETH_P_IPV6), &offset))
-		return NF_ACCEPT;
-
-	if (nf_flow_tuple_ipv6(skb, state->in, &tuple, &hdrsize, offset) < 0)
-		return NF_ACCEPT;
-
-	tuplehash = flow_offload_lookup(flow_table, &tuple);
-	if (tuplehash == NULL)
-		return NF_ACCEPT;
 
 	dir = tuplehash->tuple.dir;
 	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 
-	mtu = flow->tuplehash[dir].tuple.mtu + offset;
+	mtu = flow->tuplehash[dir].tuple.mtu + ctx->offset;
 	if (unlikely(nf_flow_exceeds_mtu(skb, mtu)))
-		return NF_ACCEPT;
+		return 0;
 
-	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + offset);
-	thoff = sizeof(*ip6h) + offset;
+	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + ctx->offset);
+	thoff = sizeof(*ip6h) + ctx->offset;
 	if (nf_flow_state_check(flow, ip6h->nexthdr, skb, thoff))
-		return NF_ACCEPT;
+		return 0;
 
 	if (!nf_flow_dst_check(&tuplehash->tuple)) {
 		flow_offload_teardown(flow);
-		return NF_ACCEPT;
+		return 0;
 	}
 
-	if (skb_try_make_writable(skb, thoff + hdrsize))
-		return NF_DROP;
+	if (skb_try_make_writable(skb, thoff + ctx->hdrsize))
+		return -1;
 
 	flow_offload_refresh(flow_table, flow);
 
@@ -698,6 +679,52 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 	if (flow_table->flags & NF_FLOWTABLE_COUNTER)
 		nf_ct_acct_update(flow->ct, tuplehash->tuple.dir, skb->len);
 
+	return 1;
+}
+
+static struct flow_offload_tuple_rhash *
+nf_flow_offload_ipv6_lookup(struct nf_flowtable_ctx *ctx,
+			    struct nf_flowtable *flow_table,
+			    struct sk_buff *skb)
+{
+	struct flow_offload_tuple tuple = {};
+
+	if (skb->protocol != htons(ETH_P_IPV6) &&
+	    !nf_flow_skb_encap_protocol(skb, htons(ETH_P_IPV6), &ctx->offset))
+		return NULL;
+
+	if (nf_flow_tuple_ipv6(ctx, skb, &tuple) < 0)
+		return NULL;
+
+	return flow_offload_lookup(flow_table, &tuple);
+}
+
+unsigned int
+nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
+			  const struct nf_hook_state *state)
+{
+	struct flow_offload_tuple_rhash *tuplehash;
+	struct nf_flowtable *flow_table = priv;
+	enum flow_offload_tuple_dir dir;
+	struct nf_flowtable_ctx ctx = {
+		.in	= state->in,
+	};
+	const struct in6_addr *nexthop;
+	struct flow_offload *flow;
+	struct net_device *outdev;
+	struct rt6_info *rt;
+	int ret;
+
+	tuplehash = nf_flow_offload_ipv6_lookup(&ctx, flow_table, skb);
+	if (tuplehash == NULL)
+		return NF_ACCEPT;
+
+	ret = nf_flow_offload_ipv6_forward(&ctx, flow_table, tuplehash, skb);
+	if (ret < 0)
+		return NF_DROP;
+	else if (ret == 0)
+		return NF_ACCEPT;
+
 	if (unlikely(tuplehash->tuple.xmit_type == FLOW_OFFLOAD_XMIT_XFRM)) {
 		rt = (struct rt6_info *)tuplehash->tuple.dst_cache;
 		memset(skb->cb, 0, sizeof(struct inet6_skb_parm));
@@ -706,6 +733,9 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 		return nf_flow_xmit_xfrm(skb, state, &rt->dst);
 	}
 
+	dir = tuplehash->tuple.dir;
+	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
+
 	switch (tuplehash->tuple.xmit_type) {
 	case FLOW_OFFLOAD_XMIT_NEIGH:
 		rt = (struct rt6_info *)tuplehash->tuple.dst_cache;