[NET]: Add software TSOv4

This patch adds the GSO implementation for IPv4 TCP.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 126 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 368d98578c14..8e5044ba3ab6 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1842,6 +1842,132 @@ unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
 
 EXPORT_SYMBOL_GPL(skb_pull_rcsum);
 
+/**
+ *	skb_segment - Perform protocol segmentation on skb.
+ *	@skb: buffer to segment
+ *	@sg: whether scatter-gather can be used for generated segments
+ *
+ *	This function performs segmentation on the given skb.  It returns
+ *	the segment at the given position.  It returns NULL if there are
+ *	no more segments to generate, or when an error is encountered.
+ */
+struct sk_buff *skb_segment(struct sk_buff *skb, int sg)
+{
+	struct sk_buff *segs = NULL;
+	struct sk_buff *tail = NULL;
+	unsigned int mss = skb_shinfo(skb)->gso_size;
+	unsigned int doffset = skb->data - skb->mac.raw;
+	unsigned int offset = doffset;
+	unsigned int headroom;
+	unsigned int len;
+	int nfrags = skb_shinfo(skb)->nr_frags;
+	int err = -ENOMEM;
+	int i = 0;
+	int pos;
+
+	__skb_push(skb, doffset);
+	headroom = skb_headroom(skb);
+	pos = skb_headlen(skb);
+
+	do {
+		struct sk_buff *nskb;
+		skb_frag_t *frag;
+		int hsize, nsize;
+		int k;
+		int size;
+
+		len = skb->len - offset;
+		if (len > mss)
+			len = mss;
+
+		hsize = skb_headlen(skb) - offset;
+		if (hsize < 0)
+			hsize = 0;
+		nsize = hsize + doffset;
+		if (nsize > len + doffset || !sg)
+			nsize = len + doffset;
+
+		nskb = alloc_skb(nsize + headroom, GFP_ATOMIC);
+		if (unlikely(!nskb))
+			goto err;
+
+		if (segs)
+			tail->next = nskb;
+		else
+			segs = nskb;
+		tail = nskb;
+
+		nskb->dev = skb->dev;
+		nskb->priority = skb->priority;
+		nskb->protocol = skb->protocol;
+		nskb->dst = dst_clone(skb->dst);
+		memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
+		nskb->pkt_type = skb->pkt_type;
+		nskb->mac_len = skb->mac_len;
+
+		skb_reserve(nskb, headroom);
+		nskb->mac.raw = nskb->data;
+		nskb->nh.raw = nskb->data + skb->mac_len;
+		nskb->h.raw = nskb->nh.raw + (skb->h.raw - skb->nh.raw);
+		memcpy(skb_put(nskb, doffset), skb->data, doffset);
+
+		if (!sg) {
+			nskb->csum = skb_copy_and_csum_bits(skb, offset,
+							    skb_put(nskb, len),
+							    len, 0);
+			continue;
+		}
+
+		frag = skb_shinfo(nskb)->frags;
+		k = 0;
+
+		nskb->ip_summed = CHECKSUM_HW;
+		nskb->csum = skb->csum;
+		memcpy(skb_put(nskb, hsize), skb->data + offset, hsize);
+
+		while (pos < offset + len) {
+			BUG_ON(i >= nfrags);
+
+			*frag = skb_shinfo(skb)->frags[i];
+			get_page(frag->page);
+			size = frag->size;
+
+			if (pos < offset) {
+				frag->page_offset += offset - pos;
+				frag->size -= offset - pos;
+			}
+
+			k++;
+
+			if (pos + size <= offset + len) {
+				i++;
+				pos += size;
+			} else {
+				frag->size -= pos + size - (offset + len);
+				break;
+			}
+
+			frag++;
+		}
+
+		skb_shinfo(nskb)->nr_frags = k;
+		nskb->data_len = len - hsize;
+		nskb->len += nskb->data_len;
+		nskb->truesize += nskb->data_len;
+	} while ((offset += len) < skb->len);
+
+	return segs;
+
+err:
+	while ((skb = segs)) {
+		segs = skb->next;
+		kfree(skb);
+	}
+	return ERR_PTR(err);
+}
+
+EXPORT_SYMBOL_GPL(skb_segment);
+
 void __init skb_init(void)
 {
 	skbuff_head_cache = kmem_cache_create("skbuff_head_cache",