Commit:     fb93134dfc2a6e6fbedc7c270a31da03fce88db9
Parent:     18b2b7bd09811779309592a10080fe9ffb93144d
Author:     Herbert Xu <[EMAIL PROTECTED]>
AuthorDate: Wed Nov 14 15:45:21 2007 -0800
Committer:  David S. Miller <[EMAIL PROTECTED]>
CommitDate: Wed Nov 14 15:45:21 2007 -0800

    [TCP]: Fix size calculation in sk_stream_alloc_pskb
    We round up the header size in sk_stream_alloc_pskb so that
    TSO packets get zero tail room.  Unfortunately this rounding
    up is not coordinated with the select_size() function used by
    TCP to calculate the second parameter of sk_stream_alloc_pskb.
    As a result, we may allocate more than a page of data in the
    non-TSO case when exactly one page is desired.
    In fact, rounding up the head room is detrimental in the non-TSO
    case because it makes memory that would otherwise be available to
    the payload head room.  TSO doesn't need this either, all it wants
    is the guarantee that there is no tail room.
    So this patch fixes this by adjusting the skb_reserve call so that
    exactly the requested amount (which all callers have calculated in
    a precise way) is made available as tail room.
    Signed-off-by: Herbert Xu <[EMAIL PROTECTED]>
    Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
 include/net/sock.h |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 5504fb9..567e468 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1235,14 +1235,16 @@ static inline struct sk_buff 
*sk_stream_alloc_pskb(struct sock *sk,
                                                   gfp_t gfp)
        struct sk_buff *skb;
-       int hdr_len;
-       hdr_len = SKB_DATA_ALIGN(sk->sk_prot->max_header);
-       skb = alloc_skb_fclone(size + hdr_len, gfp);
+       skb = alloc_skb_fclone(size + sk->sk_prot->max_header, gfp);
        if (skb) {
                skb->truesize += mem;
                if (sk_stream_wmem_schedule(sk, skb->truesize)) {
-                       skb_reserve(skb, hdr_len);
+                       /*
+                        * Make sure that we have exactly size bytes
+                        * available to the caller, no more, no less.
+                        */
+                       skb_reserve(skb, skb_tailroom(skb) - size);
                        return skb;
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