Subject: [Patch net-next v3 4/4] ipv6: Add generic UDP Tunnel segmentation

From: Cong Wang <[email-masked]>
Date: Mon, 8 Apr 2013 10:18:55 +0800

From: Cong Wang <[email-masked]>

Similar to commit 731362674580cb0c696cd1b1a03d8461a10cf90a
(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 <[email-masked]>
Cc: Pravin B Shelar <[email-masked]>
Cc: Stephen Hemminger <[email-masked]>
Cc: David S. Miller <[email-masked]>
Signed-off-by: Cong Wang <[email-masked]>
---
 net/ipv6/ip6_offload.c |    4 +-
 net/ipv6/udp_offload.c |  155 +++++++++++++++++++++++++++++++++---------------
 2 files changed, 110 insertions(+), 49 deletions(-)

diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 71b766e..f031ccf 100644
--- a/net/ipv6/ip6_offload.c
+++ b/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 |
@@ -105,6 +106,7 @@ 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);
@@ -125,7 +127,7 @@ 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);
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index 3bb3a89..bbde7ba 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -21,26 +21,81 @@ 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;
 
-	ipv6h = ipv6_hdr(skb);
-	uh = udp_hdr(skb);
+	if (likely(!skb->encapsulation)) {
+		ipv6h = ipv6_hdr(skb);
+		uh = udp_hdr(skb);
+
+		uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
+					     IPPROTO_UDP, 0);
+		skb->csum_start = skb_transport_header(skb) - skb->head;
+		skb->csum_offset = offsetof(struct udphdr, check);
+		skb->ip_summed = CHECKSUM_PARTIAL;
+	}
 
-	uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
-				     IPPROTO_UDP, 0);
-	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;
+		int udp_offset = outer_hlen - tnl_hlen;
+
+		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);
+
+		/* csum segment if tunnel sets skb with csum. */
+		if (unlikely(uh->check)) {
+			struct ipv6hdr *iph = ipv6_hdr(skb);
+
+			uh->check = csum_ipv6_magic(&iph->saddr, &iph->daddr,
+						       skb->len - udp_offset,
+						       IPPROTO_UDP, 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)
+					 netdev_features_t features)
 {
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	unsigned int mss;
@@ -73,43 +128,47 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 		goto out;
 	}
 
-	/* Do software UFO. Complete and fill in the UDP checksum as HW cannot
-	 * do checksum of UDP packets sent as multiple IP fragments.
-	 */
-	offset = skb_checksum_start_offset(skb);
-	csum = skb_checksum(skb, offset, skb->len - offset, 0);
-	offset += skb->csum_offset;
-	*(__sum16 *)(skb->data + offset) = csum_fold(csum);
-	skb->ip_summed = CHECKSUM_NONE;
-
-	/* Check if there is enough headroom to insert fragment header. */
-	if ((skb_mac_header(skb) < skb->head + frag_hdr_sz) &&
-	    pskb_expand_head(skb, frag_hdr_sz, 0, GFP_ATOMIC))
-		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.
+		 */
+		offset = skb_checksum_start_offset(skb);
+		csum = skb_checksum(skb, offset, skb->len - offset, 0);
+		offset += skb->csum_offset;
+		*(__sum16 *)(skb->data + offset) = csum_fold(csum);
+		skb->ip_summed = CHECKSUM_NONE;
+
+		/* Check if there is enough headroom to insert fragment header. */
+		if ((skb_mac_header(skb) < skb->head + frag_hdr_sz) &&
+		    pskb_expand_head(skb, frag_hdr_sz, 0, GFP_ATOMIC))
+			goto out;
 
-	/* Find the unfragmentable header and shift it left by frag_hdr_sz
-	 * bytes to insert fragment header.
-	 */
-	unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
-	nexthdr = *prevhdr;
-	*prevhdr = NEXTHDR_FRAGMENT;
-	unfrag_len = skb_network_header(skb) - skb_mac_header(skb) +
-		     unfrag_ip6hlen;
-	mac_start = skb_mac_header(skb);
-	memmove(mac_start-frag_hdr_sz, mac_start, unfrag_len);
-
-	skb->mac_header -= frag_hdr_sz;
-	skb->network_header -= frag_hdr_sz;
-
-	fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
-	fptr->nexthdr = nexthdr;
-	fptr->reserved = 0;
-	ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
-
-	/* Fragment the skb. ipv6 header and the remaining fields of the
-	 * fragment header are updated in ipv6_gso_segment()
-	 */
-	segs = skb_segment(skb, features);
+		/* Find the unfragmentable header and shift it left by frag_hdr_sz
+		 * bytes to insert fragment header.
+		 */
+		unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
+		nexthdr = *prevhdr;
+		*prevhdr = NEXTHDR_FRAGMENT;
+		unfrag_len = skb_network_header(skb) - skb_mac_header(skb) +
+			     unfrag_ip6hlen;
+		mac_start = skb_mac_header(skb);
+		memmove(mac_start-frag_hdr_sz, mac_start, unfrag_len);
+
+		skb->mac_header -= frag_hdr_sz;
+		skb->network_header -= frag_hdr_sz;
+
+		fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
+		fptr->nexthdr = nexthdr;
+		fptr->reserved = 0;
+		ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
+
+		/* Fragment the skb. ipv6 header and the remaining fields of the
+		 * fragment header are updated in ipv6_gso_segment()
+		 */
+		segs = skb_segment(skb, features);
+	}
 
 out:
 	return segs;
-- 
1.7.7.6