ipv6: Add generic UDP Tunnel segmentation

Similar to commit 7313626745
(tunneling: Add generic Tunnel segmentation)

This patch adds generic tunneling offloading support for
IPv6-UDP based tunnels.

This can be used by tunneling protocols like VXLAN.

Cc: Jesse Gross <jesse@nicira.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_offload.c

@@ -91,6 +91,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	unsigned int unfrag_ip6hlen;
 	u8 *prevhdr;
 	int offset = 0;
+	bool tunnel;
 
 	if (unlikely(skb_shinfo(skb)->gso_type &
 		     ~(SKB_GSO_UDP |
@@ -106,6 +107,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	if (unlikely(!pskb_may_pull(skb, sizeof(*ipv6h))))
 		goto out;
 
+	tunnel = skb->encapsulation;
 	ipv6h = ipv6_hdr(skb);
 	__skb_pull(skb, sizeof(*ipv6h));
 	segs = ERR_PTR(-EPROTONOSUPPORT);
@@ -126,7 +128,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 		ipv6h = ipv6_hdr(skb);
 		ipv6h->payload_len = htons(skb->len - skb->mac_len -
 					   sizeof(*ipv6h));
-		if (proto == IPPROTO_UDP) {
+		if (!tunnel && proto == IPPROTO_UDP) {
 			unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
 			fptr = (struct frag_hdr *)(skb_network_header(skb) +
 				unfrag_ip6hlen);

net/ipv6/udp_offload.c

@@ -21,13 +21,10 @@ static int udp6_ufo_send_check(struct sk_buff *skb)
 	const struct ipv6hdr *ipv6h;
 	struct udphdr *uh;
 
-	/* UDP Tunnel offload on ipv6 is not yet supported. */
-	if (skb->encapsulation)
-		return -EINVAL;
-
 	if (!pskb_may_pull(skb, sizeof(*uh)))
 		return -EINVAL;
 
+	if (likely(!skb->encapsulation)) {
 		ipv6h = ipv6_hdr(skb);
 		uh = udp_hdr(skb);
 
@@ -36,9 +33,65 @@ static int udp6_ufo_send_check(struct sk_buff *skb)
 		skb->csum_start = skb_transport_header(skb) - skb->head;
 		skb->csum_offset = offsetof(struct udphdr, check);
 		skb->ip_summed = CHECKSUM_PARTIAL;
+	}
+
 	return 0;
 }
 
+static struct sk_buff *skb_udp6_tunnel_segment(struct sk_buff *skb,
+					       netdev_features_t features)
+{
+	struct sk_buff *segs = ERR_PTR(-EINVAL);
+	int mac_len = skb->mac_len;
+	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
+	int outer_hlen;
+	netdev_features_t enc_features;
+
+	if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
+		goto out;
+
+	skb->encapsulation = 0;
+	__skb_pull(skb, tnl_hlen);
+	skb_reset_mac_header(skb);
+	skb_set_network_header(skb, skb_inner_network_offset(skb));
+	skb->mac_len = skb_inner_network_offset(skb);
+
+	/* segment inner packet. */
+	enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
+	segs = skb_mac_gso_segment(skb, enc_features);
+	if (!segs || IS_ERR(segs))
+		goto out;
+
+	outer_hlen = skb_tnl_header_len(skb);
+	skb = segs;
+	do {
+		struct udphdr *uh;
+		struct ipv6hdr *ipv6h;
+		int udp_offset = outer_hlen - tnl_hlen;
+		u32 len;
+
+		skb->mac_len = mac_len;
+
+		skb_push(skb, outer_hlen);
+		skb_reset_mac_header(skb);
+		skb_set_network_header(skb, mac_len);
+		skb_set_transport_header(skb, udp_offset);
+		uh = udp_hdr(skb);
+		uh->len = htons(skb->len - udp_offset);
+		ipv6h = ipv6_hdr(skb);
+		len = skb->len - udp_offset;
+
+		uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
+					     len, IPPROTO_UDP, 0);
+		uh->check = csum_fold(skb_checksum(skb, udp_offset, len, 0));
+		if (uh->check == 0)
+			uh->check = CSUM_MANGLED_0;
+		skb->ip_summed = CHECKSUM_NONE;
+	} while ((skb = skb->next));
+out:
+	return segs;
+}
+
 static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 					 netdev_features_t features)
 {
@@ -75,6 +128,9 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 		goto out;
 	}
 
+	if (skb->encapsulation && skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
+		segs = skb_udp6_tunnel_segment(skb, features);
+	else {
 		/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 		 * do checksum of UDP packets sent as multiple IP fragments.
 		 */
@@ -115,6 +171,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 		 * fragment header are updated in ipv6_gso_segment()
 		 */
 		segs = skb_segment(skb, features);
+	}
 
 out:
 	return segs;