tree 160f85e7d9ec1df2432b4dd3fae315812558bd10
parent b8259d9ad1d0f8d0c5ea0e37bb15080b0bd395b5
author David S. Miller <davem@davemloft.net> 1120601845 -0700
committer David S. Miller <davem@davemloft.net> 1120601845 -0700

[TCP]: Simplify SKB data portion allocation with NETIF_F_SG.

The ideal and most optimal layout for an SKB when doing
scatter-gather is to put all the headers at skb->data, and
all the user data in the page array.

This makes SKB splitting and combining extremely simple,
especially before a packet goes onto the wire the first
time.

So, when sk_stream_alloc_pskb() is given a zero size, make
sure there is no skb_tailroom().  This is achieved by applying
SKB_DATA_ALIGN() to the header length used here.

Next, make select_size() in TCP output segmentation use a
length of zero when NETIF_F_SG is true on the outgoing
interface.

Signed-off-by: David S. Miller <davem@davemloft.net>