[PATCH net-next v2] xen-netfront: Add support for IPv6 offloads

[Paul Durrant <paul.durrant@citrix.com>]

This patch adds support for IPv6 checksum offload and GSO when those
features are available in the backend.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
---

v2:
 - Addressed comments raised by Ian Campbell

 drivers/net/xen-netfront.c |  226 ++++++++++++++++++++++++++++++++++++++++----
 include/linux/ipv6.h       |    2 +
 2 files changed, 211 insertions(+), 17 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index dd1011e..afadfb5 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -616,7 +616,9 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		tx->flags |= XEN_NETTXF_extra_info;
 
 		gso->u.gso.size = skb_shinfo(skb)->gso_size;
-		gso->u.gso.type = XEN_NETIF_GSO_TYPE_TCPV4;
+		gso->u.gso.type = (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) ?
+			          XEN_NETIF_GSO_TYPE_TCPV6 :
+			          XEN_NETIF_GSO_TYPE_TCPV4;
 		gso->u.gso.pad = 0;
 		gso->u.gso.features = 0;
 
@@ -808,15 +810,18 @@ static int xennet_set_skb_gso(struct sk_buff *skb,
 		return -EINVAL;
 	}
 
-	/* Currently only TCPv4 S.O. is supported. */
-	if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4) {
+	if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4 &&
+	    gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV6) {
 		if (net_ratelimit())
 			pr_warn("Bad GSO type %d\n", gso->u.gso.type);
 		return -EINVAL;
 	}
 
 	skb_shinfo(skb)->gso_size = gso->u.gso.size;
-	skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
+	skb_shinfo(skb)->gso_type =
+		(gso->u.gso.type == XEN_NETIF_GSO_TYPE_TCPV4) ?
+		SKB_GSO_TCPV4 :
+		SKB_GSO_TCPV6;
 
 	/* Header must be checked, and gso_segs computed. */
 	skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
@@ -856,11 +861,34 @@ static RING_IDX xennet_fill_frags(struct netfront_info *np,
 	return cons;
 }
 
-static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
+static inline bool maybe_pull_tail(struct sk_buff *skb, unsigned int len)
 {
-	struct iphdr *iph;
-	int err = -EPROTO;
+	int target;
+
+	if (!skb_is_nonlinear(skb) || skb_headlen(skb) >= len)
+		return true;
+
+	/* If we need to pullup then pullup to the max, so we
+	 * won't need to do it again.
+	 */
+	target = min_t(int, skb->len, MAX_TCP_HEADER);
+	__pskb_pull_tail(skb, target - skb_headlen(skb));
+
+	if (skb_headlen(skb) < len) {
+		net_err_ratelimited("Failed to pullup packet header\n");
+		return false;    
+	}
+
+	return true;
+}
+
+static int checksum_setup_ip(struct net_device *dev, struct sk_buff *skb)
+{
+	struct iphdr *iph = (void *)skb->data;
+	unsigned int header_size;
+	unsigned int off;
 	int recalculate_partial_csum = 0;
+	int err = -EPROTO;
 
 	/*
 	 * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
@@ -879,40 +907,56 @@ static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
 	if (skb->ip_summed != CHECKSUM_PARTIAL)
 		return 0;
 
-	if (skb->protocol != htons(ETH_P_IP))
+	off = sizeof(struct iphdr);
+
+	header_size = skb->network_header + off;
+	if (!maybe_pull_tail(skb, header_size))
 		goto out;
 
-	iph = (void *)skb->data;
+	off = iph->ihl * 4;
 
 	switch (iph->protocol) {
 	case IPPROTO_TCP:
-		if (!skb_partial_csum_set(skb, 4 * iph->ihl,
+		if (!skb_partial_csum_set(skb, off,
 					  offsetof(struct tcphdr, check)))
 			goto out;
 
 		if (recalculate_partial_csum) {
 			struct tcphdr *tcph = tcp_hdr(skb);
+
+			header_size = skb->network_header +
+				off +
+				sizeof(struct tcphdr);
+			if (!maybe_pull_tail(skb, header_size))
+				goto out;
+
 			tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
-							 skb->len - iph->ihl*4,
+							 skb->len - off,
 							 IPPROTO_TCP, 0);
 		}
 		break;
 	case IPPROTO_UDP:
-		if (!skb_partial_csum_set(skb, 4 * iph->ihl,
+		if (!skb_partial_csum_set(skb, off,
 					  offsetof(struct udphdr, check)))
 			goto out;
 
 		if (recalculate_partial_csum) {
 			struct udphdr *udph = udp_hdr(skb);
+
+			header_size = skb->network_header +
+				off +
+				sizeof(struct udphdr);
+			if (!maybe_pull_tail(skb, header_size))
+				goto out;
+
 			udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
-							 skb->len - iph->ihl*4,
+							 skb->len - off,
 							 IPPROTO_UDP, 0);
 		}
 		break;
 	default:
-		if (net_ratelimit())
-			pr_err("Attempting to checksum a non-TCP/UDP packet, dropping a protocol %d packet\n",
-			       iph->protocol);
+		net_err_ratelimited("Attempting to checksum a non-TCP/UDP packet, dropping a protocol %d packet\n",
+				    iph->protocol);
 		goto out;
 	}
 
@@ -922,6 +966,122 @@ out:
 	return err;
 }
 
+static int checksum_setup_ipv6(struct net_device *dev, struct sk_buff *skb)
+{
+	struct ipv6hdr *ipv6h = (void *)skb->data;
+	u8 nexthdr;
+	unsigned int header_size;
+	unsigned int off;
+	bool fragment;
+	bool done;
+	int err = -EPROTO;
+
+	done = false;
+
+	/* A non-CHECKSUM_PARTIAL SKB does not require setup. */
+	if (skb->ip_summed != CHECKSUM_PARTIAL)
+		return 0;
+
+	off = sizeof(struct ipv6hdr);
+
+	header_size = skb->network_header + off;
+	if (!maybe_pull_tail(skb, header_size))
+		goto out;
+
+	nexthdr = ipv6h->nexthdr;
+
+	while ((off <= sizeof(struct ipv6hdr) + ntohs(ipv6h->payload_len)) &&
+	       !done) {
+		switch (nexthdr) {
+		case IPPROTO_DSTOPTS:
+		case IPPROTO_HOPOPTS:
+		case IPPROTO_ROUTING: {
+			struct ipv6_opt_hdr *hp = (void *)(skb->data + off);
+
+			header_size = skb->network_header +
+				off +
+				sizeof(struct ipv6_opt_hdr);
+			if (!maybe_pull_tail(skb, header_size))
+				goto out;
+
+			nexthdr = hp->nexthdr;
+			off += ipv6_optlen(hp);
+			break;
+		}
+		case IPPROTO_AH: {
+			struct ip_auth_hdr *hp = (void *)(skb->data + off);
+
+			header_size = skb->network_header +
+				off +
+				sizeof(struct ip_auth_hdr);
+			if (!maybe_pull_tail(skb, header_size))
+				goto out;
+
+			nexthdr = hp->nexthdr;
+			off += ipv6_ahlen(hp);
+			break;
+		}
+		case IPPROTO_FRAGMENT:
+			fragment = true;
+			/* fall through */
+		default:
+			done = true;
+			break;
+		}
+	}
+
+	if (!done) {
+		net_err_ratelimited("Failed to parse packet header\n");
+		goto out;
+	}
+
+	if (fragment) {
+		net_err_ratelimited("Packet is a fragment!\n");
+		goto out;
+	}
+
+	switch (nexthdr) {
+	case IPPROTO_TCP:
+		if (!skb_partial_csum_set(skb, off,
+					  offsetof(struct tcphdr, check)))
+			goto out;
+		break;
+	case IPPROTO_UDP:
+		if (!skb_partial_csum_set(skb, off,
+					  offsetof(struct udphdr, check)))
+			goto out;
+		break;
+	default:
+		net_err_ratelimited("Attempting to checksum a non-TCP/UDP packet, dropping a protocol %d packet\n",
+				    nexthdr);
+		goto out;
+	}
+
+	err = 0;
+
+out:
+	return err;
+}
+
+static int checksum_setup(struct net_device *dev, struct sk_buff *skb)
+{
+	int err;
+
+	switch (skb->protocol) {
+	case htons(ETH_P_IP):
+		err = checksum_setup_ip(dev, skb);
+		break;
+	case htons(ETH_P_IPV6):
+		err = checksum_setup_ipv6(dev, skb);
+		break;
+	default:
+		err = -EPROTO;
+		break;
+	}
+
+	return err;
+}
+
 static int handle_incoming_queue(struct net_device *dev,
 				 struct sk_buff_head *rxq)
 {
@@ -1232,6 +1392,15 @@ static netdev_features_t xennet_fix_features(struct net_device *dev,
 			features &= ~NETIF_F_SG;
 	}
 
+	if (features & NETIF_F_IPV6_CSUM) {
+		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+				 "feature-ipv6-csum-offload", "%d", &val) < 0)
+			val = 0;
+
+		if (!val)
+			features &= ~NETIF_F_IPV6_CSUM;
+	}
+
 	if (features & NETIF_F_TSO) {
 		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
 				 "feature-gso-tcpv4", "%d", &val) < 0)
@@ -1241,6 +1410,15 @@ static netdev_features_t xennet_fix_features(struct net_device *dev,
 			features &= ~NETIF_F_TSO;
 	}
 
+	if (features & NETIF_F_TSO6) {
+		if (xenbus_scanf(XBT_NIL, np->xbdev->otherend,
+				 "feature-gso-tcpv6", "%d", &val) < 0)
+			val = 0;
+
+		if (!val)
+			features &= ~NETIF_F_TSO6;
+	}
+
 	return features;
 }
 
@@ -1373,7 +1551,9 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
 	netif_napi_add(netdev, &np->napi, xennet_poll, 64);
 	netdev->features        = NETIF_F_IP_CSUM | NETIF_F_RXCSUM |
 				  NETIF_F_GSO_ROBUST;
-	netdev->hw_features	= NETIF_F_IP_CSUM | NETIF_F_SG | NETIF_F_TSO;
+	netdev->hw_features	= NETIF_F_SG | 
+		                  NETIF_F_IPV6_CSUM |
+		                  NETIF_F_TSO | NETIF_F_TSO6;
 
 	/*
          * Assume that all hw features are available for now. This set
@@ -1751,6 +1931,18 @@ again:
 		goto abort_transaction;
 	}
 
+	err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv6", "%d", 1);
+	if (err) {
+		message = "writing feature-gso-tcpv6";
+		goto abort_transaction;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "feature-ipv6-csum-offload", "%d", 1);
+	if (err) {
+		message = "writing feature-gso-tcpv6";
+		goto abort_transaction;
+	}
+
 	err = xenbus_transaction_end(xbt, 0);
 	if (err) {
 		if (err == -EAGAIN)
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 5d89d1b..10f1b03 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -4,6 +4,8 @@
 #include <uapi/linux/ipv6.h>
 
 #define ipv6_optlen(p)  (((p)->hdrlen+1) << 3)
+#define ipv6_ahlen(p)   (((p)->hdrlen+2) << 2);
+
 /*
  * This structure contains configuration options per IPv6 link.
  */
-- 
1.7.10.4