net: Changes to ip_tunnel to support foo-over-udp encapsulation

This patch changes IP tunnel to support (secondary) encapsulation,
Foo-over-UDP. Changes include:

1) Adding tun_hlen as the tunnel header length, encap_hlen as the
   encapsulation header length, and hlen becomes the grand total
   of these.
2) Added common netlink define to support FOU encapsulation.
3) Routines to perform FOU encapsulation.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 90 insertions, 1 deletions

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index afed1aa..e3a3dc9 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -55,6 +55,7 @@
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
+#include <net/udp.h>
 
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6.h>
@@ -487,6 +488,91 @@ drop:
 }
 EXPORT_SYMBOL_GPL(ip_tunnel_rcv);
 
+static int ip_encap_hlen(struct ip_tunnel_encap *e)
+{
+	switch (e->type) {
+	case TUNNEL_ENCAP_NONE:
+		return 0;
+	case TUNNEL_ENCAP_FOU:
+		return sizeof(struct udphdr);
+	default:
+		return -EINVAL;
+	}
+}
+
+int ip_tunnel_encap_setup(struct ip_tunnel *t,
+			  struct ip_tunnel_encap *ipencap)
+{
+	int hlen;
+
+	memset(&t->encap, 0, sizeof(t->encap));
+
+	hlen = ip_encap_hlen(ipencap);
+	if (hlen < 0)
+		return hlen;
+
+	t->encap.type = ipencap->type;
+	t->encap.sport = ipencap->sport;
+	t->encap.dport = ipencap->dport;
+	t->encap.flags = ipencap->flags;
+
+	t->encap_hlen = hlen;
+	t->hlen = t->encap_hlen + t->tun_hlen;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ip_tunnel_encap_setup);
+
+static int fou_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e,
+			    size_t hdr_len, u8 *protocol, struct flowi4 *fl4)
+{
+	struct udphdr *uh;
+	__be16 sport;
+	bool csum = !!(e->flags & TUNNEL_ENCAP_FLAG_CSUM);
+	int type = csum ? SKB_GSO_UDP_TUNNEL_CSUM : SKB_GSO_UDP_TUNNEL;
+
+	skb = iptunnel_handle_offloads(skb, csum, type);
+
+	if (IS_ERR(skb))
+		return PTR_ERR(skb);
+
+	/* Get length and hash before making space in skb */
+
+	sport = e->sport ? : udp_flow_src_port(dev_net(skb->dev),
+					       skb, 0, 0, false);
+
+	skb_push(skb, hdr_len);
+
+	skb_reset_transport_header(skb);
+	uh = udp_hdr(skb);
+
+	uh->dest = e->dport;
+	uh->source = sport;
+	uh->len = htons(skb->len);
+	uh->check = 0;
+	udp_set_csum(!(e->flags & TUNNEL_ENCAP_FLAG_CSUM), skb,
+		     fl4->saddr, fl4->daddr, skb->len);
+
+	*protocol = IPPROTO_UDP;
+
+	return 0;
+}
+
+int ip_tunnel_encap(struct sk_buff *skb, struct ip_tunnel *t,
+		    u8 *protocol, struct flowi4 *fl4)
+{
+	switch (t->encap.type) {
+	case TUNNEL_ENCAP_NONE:
+		return 0;
+	case TUNNEL_ENCAP_FOU:
+		return fou_build_header(skb, &t->encap, t->encap_hlen,
+					protocol, fl4);
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL(ip_tunnel_encap);
+
 static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb,
 			    struct rtable *rt, __be16 df)
 {
@@ -536,7 +622,7 @@ static int tnl_update_pmtu(struct net_device *dev, struct sk_buff *skb,
 }
 
 void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
-		    const struct iphdr *tnl_params, const u8 protocol)
+		    const struct iphdr *tnl_params, u8 protocol)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
 	const struct iphdr *inner_iph;
@@ -617,6 +703,9 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
 	init_tunnel_flow(&fl4, protocol, dst, tnl_params->saddr,
 			 tunnel->parms.o_key, RT_TOS(tos), tunnel->parms.link);
 
+	if (ip_tunnel_encap(skb, tunnel, &protocol, &fl4) < 0)
+		goto tx_error;
+
 	rt = connected ? tunnel_rtable_get(tunnel, 0, &fl4.saddr) : NULL;
 
 	if (!rt) {