[IPv4/IPv6]: UFO Scatter-gather approach

Attached is kernel patch for UDP Fragmentation Offload (UFO) feature.

1. This patch incorporate the review comments by Jeff Garzik.
2. Renamed USO as UFO (UDP Fragmentation Offload)
3. udp sendfile support with UFO

This patches uses scatter-gather feature of skb to generate large UDP
datagram. Below is a "how-to" on changes required in network device
driver to use the UFO interface.

UDP Fragmentation Offload (UFO) Interface:
-------------------------------------------
UFO is a feature wherein the Linux kernel network stack will offload the
IP fragmentation functionality of large UDP datagram to hardware. This
will reduce the overhead of stack in fragmenting the large UDP datagram to
MTU sized packets

1) Drivers indicate their capability of UFO using
dev->features |= NETIF_F_UFO | NETIF_F_HW_CSUM | NETIF_F_SG

NETIF_F_HW_CSUM is required for UFO over ipv6.

2) UFO packet will be submitted for transmission using driver xmit routine.
UFO packet will have a non-zero value for

"skb_shinfo(skb)->ufo_size"

skb_shinfo(skb)->ufo_size will indicate the length of data part in each IP
fragment going out of the adapter after IP fragmentation by hardware.

skb->data will contain MAC/IP/UDP header and skb_shinfo(skb)->frags[]
contains the data payload. The skb->ip_summed will be set to CHECKSUM_HW
indicating that hardware has to do checksum calculation. Hardware should
compute the UDP checksum of complete datagram and also ip header checksum of
each fragmented IP packet.

For IPV6 the UFO provides the fragment identification-id in
skb_shinfo(skb)->ip6_frag_id. The adapter should use this ID for generating
IPv6 fragments.

Signed-off-by: Ananda Raju <ananda.raju@neterion.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (forwarded)
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>

5 files changed, 290 insertions, 6 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index a44eeef..8d15415 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2717,6 +2717,20 @@ int register_netdevice(struct net_device *dev)
 		       dev->name);
 		dev->features &= ~NETIF_F_TSO;
 	}
+	if (dev->features & NETIF_F_UFO) {
+		if (!(dev->features & NETIF_F_HW_CSUM)) {
+			printk(KERN_ERR "%s: Dropping NETIF_F_UFO since no "
+					"NETIF_F_HW_CSUM feature.\n",
+							dev->name);
+			dev->features &= ~NETIF_F_UFO;
+		}
+		if (!(dev->features & NETIF_F_SG)) {
+			printk(KERN_ERR "%s: Dropping NETIF_F_UFO since no "
+					"NETIF_F_SG feature.\n",
+					dev->name);
+			dev->features &= ~NETIF_F_UFO;
+		}
+	}
 
 	/*
 	 *	nil rebuild_header routine,
diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index 404b761..0350586 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c
@@ -93,6 +93,20 @@ int ethtool_op_get_perm_addr(struct net_device *dev, struct ethtool_perm_addr *a
 }
  
 
+u32 ethtool_op_get_ufo(struct net_device *dev)
+{
+	return (dev->features & NETIF_F_UFO) != 0;
+}
+
+int ethtool_op_set_ufo(struct net_device *dev, u32 data)
+{
+	if (data)
+		dev->features |= NETIF_F_UFO;
+	else
+		dev->features &= ~NETIF_F_UFO;
+	return 0;
+}
+
 /* Handlers for each ethtool command */
 
 static int ethtool_get_settings(struct net_device *dev, void __user *useraddr)
@@ -483,6 +497,11 @@ static int __ethtool_set_sg(struct net_device *dev, u32 data)
 			return err;
 	}
 
+	if (!data && dev->ethtool_ops->set_ufo) {
+		err = dev->ethtool_ops->set_ufo(dev, 0);
+		if (err)
+			return err;
+	}
 	return dev->ethtool_ops->set_sg(dev, data);
 }
 
@@ -569,6 +588,32 @@ static int ethtool_set_tso(struct net_device *dev, char __user *useraddr)
 	return dev->ethtool_ops->set_tso(dev, edata.data);
 }
 
+static int ethtool_get_ufo(struct net_device *dev, char __user *useraddr)
+{
+	struct ethtool_value edata = { ETHTOOL_GTSO };
+
+	if (!dev->ethtool_ops->get_ufo)
+		return -EOPNOTSUPP;
+	edata.data = dev->ethtool_ops->get_ufo(dev);
+	if (copy_to_user(useraddr, &edata, sizeof(edata)))
+		 return -EFAULT;
+	return 0;
+}
+static int ethtool_set_ufo(struct net_device *dev, char __user *useraddr)
+{
+	struct ethtool_value edata;
+
+	if (!dev->ethtool_ops->set_ufo)
+		return -EOPNOTSUPP;
+	if (copy_from_user(&edata, useraddr, sizeof(edata)))
+		return -EFAULT;
+	if (edata.data && !(dev->features & NETIF_F_SG))
+		return -EINVAL;
+	if (edata.data && !(dev->features & NETIF_F_HW_CSUM))
+		return -EINVAL;
+	return dev->ethtool_ops->set_ufo(dev, edata.data);
+}
+
 static int ethtool_self_test(struct net_device *dev, char __user *useraddr)
 {
 	struct ethtool_test test;
@@ -854,6 +899,12 @@ int dev_ethtool(struct ifreq *ifr)
 	case ETHTOOL_GPERMADDR:
 		rc = ethtool_get_perm_addr(dev, useraddr);
 		break;
+	case ETHTOOL_GUFO:
+		rc = ethtool_get_ufo(dev, useraddr);
+		break;
+	case ETHTOOL_SUFO:
+		rc = ethtool_set_ufo(dev, useraddr);
+		break;
 	default:
 		rc =  -EOPNOTSUPP;
 	}
@@ -882,3 +933,5 @@ EXPORT_SYMBOL(ethtool_op_set_sg);
 EXPORT_SYMBOL(ethtool_op_set_tso);
 EXPORT_SYMBOL(ethtool_op_set_tx_csum);
 EXPORT_SYMBOL(ethtool_op_set_tx_hw_csum);
+EXPORT_SYMBOL(ethtool_op_set_ufo);
+EXPORT_SYMBOL(ethtool_op_get_ufo);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ef9d46b..95501e4 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -176,6 +176,8 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	skb_shinfo(skb)->tso_size = 0;
 	skb_shinfo(skb)->tso_segs = 0;
 	skb_shinfo(skb)->frag_list = NULL;
+	skb_shinfo(skb)->ufo_size = 0;
+	skb_shinfo(skb)->ip6_frag_id = 0;
 out:
 	return skb;
 nodata:
@@ -1696,6 +1698,78 @@ unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
 	return textsearch_find(config, state);
 }
 
+/**
+ * skb_append_datato_frags: - append the user data to a skb
+ * @sk: sock  structure
+ * @skb: skb structure to be appened with user data.
+ * @getfrag: call back function to be used for getting the user data
+ * @from: pointer to user message iov
+ * @length: length of the iov message
+ *
+ * Description: This procedure append the user data in the fragment part
+ * of the skb if any page alloc fails user this procedure returns  -ENOMEM
+ */
+int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
+			int getfrag(void *from, char *to, int offset,
+					int len, int odd, struct sk_buff *skb),
+			void *from, int length)
+{
+	int frg_cnt = 0;
+	skb_frag_t *frag = NULL;
+	struct page *page = NULL;
+	int copy, left;
+	int offset = 0;
+	int ret;
+
+	do {
+		/* Return error if we don't have space for new frag */
+		frg_cnt = skb_shinfo(skb)->nr_frags;
+		if (frg_cnt >= MAX_SKB_FRAGS)
+			return -EFAULT;
+
+		/* allocate a new page for next frag */
+		page = alloc_pages(sk->sk_allocation, 0);
+
+		/* If alloc_page fails just return failure and caller will
+		 * free previous allocated pages by doing kfree_skb()
+		 */
+		if (page == NULL)
+			return -ENOMEM;
+
+		/* initialize the next frag */
+		sk->sk_sndmsg_page = page;
+		sk->sk_sndmsg_off = 0;
+		skb_fill_page_desc(skb, frg_cnt, page, 0, 0);
+		skb->truesize += PAGE_SIZE;
+		atomic_add(PAGE_SIZE, &sk->sk_wmem_alloc);
+
+		/* get the new initialized frag */
+		frg_cnt = skb_shinfo(skb)->nr_frags;
+		frag = &skb_shinfo(skb)->frags[frg_cnt - 1];
+
+		/* copy the user data to page */
+		left = PAGE_SIZE - frag->page_offset;
+		copy = (length > left)? left : length;
+
+		ret = getfrag(from, (page_address(frag->page) +
+			    frag->page_offset + frag->size),
+			    offset, copy, 0, skb);
+		if (ret < 0)
+			return -EFAULT;
+
+		/* copy was successful so update the size parameters */
+		sk->sk_sndmsg_off += copy;
+		frag->size += copy;
+		skb->len += copy;
+		skb->data_len += copy;
+		offset += copy;
+		length -= copy;
+
+	} while (length > 0);
+
+	return 0;
+}
+
 void __init skb_init(void)
 {
 	skbuff_head_cache = kmem_cache_create("skbuff_head_cache",
@@ -1747,3 +1821,4 @@ EXPORT_SYMBOL(skb_prepare_seq_read);
 EXPORT_SYMBOL(skb_seq_read);
 EXPORT_SYMBOL(skb_abort_seq_read);
 EXPORT_SYMBOL(skb_find_text);
+EXPORT_SYMBOL(skb_append_datato_frags);
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 87e3500..1775823 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -275,7 +275,8 @@ int ip_output(struct sk_buff *skb)
 {
 	IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 
-	if (skb->len > dst_mtu(skb->dst) && !skb_shinfo(skb)->tso_size)
+	if (skb->len > dst_mtu(skb->dst) &&
+		!(skb_shinfo(skb)->ufo_size || skb_shinfo(skb)->tso_size))
 		return ip_fragment(skb, ip_finish_output);
 	else
 		return ip_finish_output(skb);
@@ -688,6 +689,60 @@ csum_page(struct page *page, int offset, int copy)
 	return csum;
 }
 
+inline int ip_ufo_append_data(struct sock *sk,
+			int getfrag(void *from, char *to, int offset, int len,
+			       int odd, struct sk_buff *skb),
+			void *from, int length, int hh_len, int fragheaderlen,
+			int transhdrlen, int mtu,unsigned int flags)
+{
+	struct sk_buff *skb;
+	int err;
+
+	/* There is support for UDP fragmentation offload by network
+	 * device, so create one single skb packet containing complete
+	 * udp datagram
+	 */
+	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
+		skb = sock_alloc_send_skb(sk,
+			hh_len + fragheaderlen + transhdrlen + 20,
+			(flags & MSG_DONTWAIT), &err);
+
+		if (skb == NULL)
+			return err;
+
+		/* reserve space for Hardware header */
+		skb_reserve(skb, hh_len);
+
+		/* create space for UDP/IP header */
+		skb_put(skb,fragheaderlen + transhdrlen);
+
+		/* initialize network header pointer */
+		skb->nh.raw = skb->data;
+
+		/* initialize protocol header pointer */
+		skb->h.raw = skb->data + fragheaderlen;
+
+		skb->ip_summed = CHECKSUM_HW;
+		skb->csum = 0;
+		sk->sk_sndmsg_off = 0;
+	}
+
+	err = skb_append_datato_frags(sk,skb, getfrag, from,
+			       (length - transhdrlen));
+	if (!err) {
+		/* specify the length of each IP datagram fragment*/
+		skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
+		__skb_queue_tail(&sk->sk_write_queue, skb);
+
+		return 0;
+	}
+	/* There is not enough support do UFO ,
+	 * so follow normal path
+	 */
+	kfree_skb(skb);
+	return err;
+}
+
 /*
  *	ip_append_data() and ip_append_page() can make one large IP datagram
  *	from many pieces of data. Each pieces will be holded on the socket
@@ -777,6 +832,15 @@ int ip_append_data(struct sock *sk,
 		csummode = CHECKSUM_HW;
 
 	inet->cork.length += length;
+	if (((length > mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
+			(rt->u.dst.dev->features & NETIF_F_UFO)) {
+
+		if(ip_ufo_append_data(sk, getfrag, from, length, hh_len,
+			       fragheaderlen, transhdrlen, mtu, flags))
+			goto error;
+
+		return 0;
+	}
 
 	/* So, what's going on in the loop below?
 	 *
@@ -1008,14 +1072,23 @@ ssize_t	ip_append_page(struct sock *sk, struct page *page,
 		return -EINVAL;
 
 	inet->cork.length += size;
+	if ((sk->sk_protocol == IPPROTO_UDP) &&
+	    (rt->u.dst.dev->features & NETIF_F_UFO))
+		skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen);
+
 
 	while (size > 0) {
 		int i;
 
-		/* Check if the remaining data fits into current packet. */
-		len = mtu - skb->len;
-		if (len < size)
-			len = maxfraglen - skb->len;
+		if (skb_shinfo(skb)->ufo_size)
+			len = size;
+		else {
+
+			/* Check if the remaining data fits into current packet. */
+			len = mtu - skb->len;
+			if (len < size)
+				len = maxfraglen - skb->len;
+		}
 		if (len <= 0) {
 			struct sk_buff *skb_prev;
 			char *data;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 563b442..614296a 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -147,7 +147,8 @@ static int ip6_output2(struct sk_buff *skb)
 
 int ip6_output(struct sk_buff *skb)
 {
-	if (skb->len > dst_mtu(skb->dst) || dst_allfrag(skb->dst))
+	if ((skb->len > dst_mtu(skb->dst) && !skb_shinfo(skb)->ufo_size) ||
+				dst_allfrag(skb->dst))
 		return ip6_fragment(skb, ip6_output2);
 	else
 		return ip6_output2(skb);
@@ -768,6 +769,65 @@ out_err_release:
 	*dst = NULL;
 	return err;
 }
+inline int ip6_ufo_append_data(struct sock *sk,
+			int getfrag(void *from, char *to, int offset, int len,
+			int odd, struct sk_buff *skb),
+			void *from, int length, int hh_len, int fragheaderlen,
+			int transhdrlen, int mtu,unsigned int flags)
+
+{
+	struct sk_buff *skb;
+	int err;
+
+	/* There is support for UDP large send offload by network
+	 * device, so create one single skb packet containing complete
+	 * udp datagram
+	 */
+	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL) {
+		skb = sock_alloc_send_skb(sk,
+			hh_len + fragheaderlen + transhdrlen + 20,
+			(flags & MSG_DONTWAIT), &err);
+		if (skb == NULL)
+			return -ENOMEM;
+
+		/* reserve space for Hardware header */
+		skb_reserve(skb, hh_len);
+
+		/* create space for UDP/IP header */
+		skb_put(skb,fragheaderlen + transhdrlen);
+
+		/* initialize network header pointer */
+		skb->nh.raw = skb->data;
+
+		/* initialize protocol header pointer */
+		skb->h.raw = skb->data + fragheaderlen;
+
+		skb->ip_summed = CHECKSUM_HW;
+		skb->csum = 0;
+		sk->sk_sndmsg_off = 0;
+	}
+
+	err = skb_append_datato_frags(sk,skb, getfrag, from,
+				      (length - transhdrlen));
+	if (!err) {
+		struct frag_hdr fhdr;
+
+		/* specify the length of each IP datagram fragment*/
+		skb_shinfo(skb)->ufo_size = (mtu - fragheaderlen) - 
+						sizeof(struct frag_hdr);
+		ipv6_select_ident(skb, &fhdr);
+		skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
+		__skb_queue_tail(&sk->sk_write_queue, skb);
+
+		return 0;
+	}
+	/* There is not enough support do UPD LSO,
+	 * so follow normal path
+	 */
+	kfree_skb(skb);
+
+	return err;
+}
 
 int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
 	int offset, int len, int odd, struct sk_buff *skb),
@@ -860,6 +920,15 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
 	 */
 
 	inet->cork.length += length;
+	if (((length > mtu) && (sk->sk_protocol == IPPROTO_UDP)) &&
+	    (rt->u.dst.dev->features & NETIF_F_UFO)) {
+
+		if(ip6_ufo_append_data(sk, getfrag, from, length, hh_len,
+				fragheaderlen, transhdrlen, mtu, flags))
+			goto error;
+
+		return 0;
+	}
 
 	if ((skb = skb_peek_tail(&sk->sk_write_queue)) == NULL)
 		goto alloc_new_skb;