On Tue, Aug 25, 2015 at 4:33 PM, Lawrence Brakmo <bra...@fb.com> wrote:
>
> Refactor tcp_skb_cb to create two overlaping areas to store
> state for incoming or outgoing skbs based on comments by
> Neal Cardwell to tcp_nv patch:
>
> AFAICT this patch would not require an increase in the size of
> sk_buff cb[] if it were to take advantage of the fact that the
> tcp_skb_cb header.h4 and header.h6 fields are only used in the packet
> reception code path, and this in_flight field is only used on the
> transmit side.
>
> Signed-off-by: Lawrence Brakmo <bra...@fb.com>
Acked-by: Yuchung Cheng <ych...@google.com>
> ---
> include/net/tcp.h | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 0121529..a086a98 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -755,11 +755,16 @@ struct tcp_skb_cb {
> /* 1 byte hole */
> __u32 ack_seq; /* Sequence number ACK'd */
> union {
> - struct inet_skb_parm h4;
> + struct {
> + /* There is space for up to 20 bytes */
> + } tx; /* only used for outgoing skbs */
> + union {
> + struct inet_skb_parm h4;
> #if IS_ENABLED(CONFIG_IPV6)
> - struct inet6_skb_parm h6;
> + struct inet6_skb_parm h6;
> #endif
> - } header; /* For incoming frames */
> + } header; /* For incoming skbs */
> + };
> };
>
> #define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))
> --
> 1.8.1
>
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