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Date: Sat, 13 Dec 2008 12:35:19 +1100
From: Herbert Xu <herbert@...dor.apana.org.au>
To: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
Evgeniy Polyakov <johnpol@....mipt.ru>,
Ben Hutchings <bhutchings@...arflare.com>
Subject: [PATCH 1/8] net: Add frag_list support to skb_segment
net: Add frag_list support to skb_segment
This patch adds limited support for handling frag_list packets in
skb_segment. The intention is to support GRO (Generic Receive Offload)
packets which will be constructed by chaining normal packets using
frag_list.
As such we require all frag_list members terminate on exact MSS
boundaries. This is checked using BUG_ON.
As there should only be one producer in the kernel of such packets,
namely GRO, this requirement should not be difficult to maintain.
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
---
net/core/skbuff.c | 73 +++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 59 insertions(+), 14 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index d49ef83..cf05a8c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2285,6 +2285,7 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features)
{
struct sk_buff *segs = NULL;
struct sk_buff *tail = NULL;
+ struct sk_buff *fskb = skb_shinfo(skb)->frag_list;
unsigned int mss = skb_shinfo(skb)->gso_size;
unsigned int doffset = skb->data - skb_mac_header(skb);
unsigned int offset = doffset;
@@ -2304,7 +2305,6 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features)
struct sk_buff *nskb;
skb_frag_t *frag;
int hsize;
- int k;
int size;
len = skb->len - offset;
@@ -2317,9 +2317,36 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features)
if (hsize > len || !sg)
hsize = len;
- nskb = alloc_skb(hsize + doffset + headroom, GFP_ATOMIC);
- if (unlikely(!nskb))
- goto err;
+ if (!hsize && i >= nfrags) {
+ BUG_ON(fskb->len != len);
+
+ pos += len;
+ nskb = skb_clone(fskb, GFP_ATOMIC);
+ fskb = fskb->next;
+
+ if (unlikely(!nskb))
+ goto err;
+
+ hsize = skb_end_pointer(nskb) - nskb->head;
+ if (skb_cow_head(nskb, doffset + headroom)) {
+ kfree_skb(nskb);
+ goto err;
+ }
+
+ nskb->truesize += skb_end_pointer(nskb) - nskb->head -
+ hsize;
+ skb_release_head_state(nskb);
+ __skb_push(nskb, doffset);
+ } else {
+ nskb = alloc_skb(hsize + doffset + headroom,
+ GFP_ATOMIC);
+
+ if (unlikely(!nskb))
+ goto err;
+
+ skb_reserve(nskb, headroom);
+ __skb_put(nskb, doffset);
+ }
if (segs)
tail->next = nskb;
@@ -2330,13 +2357,15 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features)
__copy_skb_header(nskb, skb);
nskb->mac_len = skb->mac_len;
- skb_reserve(nskb, headroom);
skb_reset_mac_header(nskb);
skb_set_network_header(nskb, skb->mac_len);
nskb->transport_header = (nskb->network_header +
skb_network_header_len(skb));
- skb_copy_from_linear_data(skb, skb_put(nskb, doffset),
- doffset);
+ skb_copy_from_linear_data(skb, nskb->data, doffset);
+
+ if (pos >= offset + len)
+ continue;
+
if (!sg) {
nskb->ip_summed = CHECKSUM_NONE;
nskb->csum = skb_copy_and_csum_bits(skb, offset,
@@ -2346,14 +2375,11 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features)
}
frag = skb_shinfo(nskb)->frags;
- k = 0;
skb_copy_from_linear_data_offset(skb, offset,
skb_put(nskb, hsize), hsize);
- while (pos < offset + len) {
- BUG_ON(i >= nfrags);
-
+ while (pos < offset + len && i < nfrags) {
*frag = skb_shinfo(skb)->frags[i];
get_page(frag->page);
size = frag->size;
@@ -2363,20 +2389,39 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features)
frag->size -= offset - pos;
}
- k++;
+ skb_shinfo(nskb)->nr_frags++;
if (pos + size <= offset + len) {
i++;
pos += size;
} else {
frag->size -= pos + size - (offset + len);
- break;
+ goto skip_fraglist;
}
frag++;
}
- skb_shinfo(nskb)->nr_frags = k;
+ if (pos < offset + len) {
+ struct sk_buff *fskb2 = fskb;
+
+ BUG_ON(pos + fskb->len != offset + len);
+
+ pos += fskb->len;
+ fskb = fskb->next;
+
+ if (fskb2->next) {
+ fskb2 = skb_clone(fskb2, GFP_ATOMIC);
+ if (!fskb2)
+ goto err;
+ } else
+ skb_get(fskb2);
+
+ BUG_ON(skb_shinfo(nskb)->frag_list);
+ skb_shinfo(nskb)->frag_list = fskb2;
+ }
+
+skip_fraglist:
nskb->data_len = len - hsize;
nskb->len += nskb->data_len;
nskb->truesize += nskb->data_len;
--
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