[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",