Commit b75803d5 authored May 06, 2016 by Lawrence Brakmo Committed by David S. Miller May 09, 2016

tcp: refactor struct tcp_skb_cb



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 <brakmo@fb.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7d945796

include/net/tcp.h

+8 −3

Original line number	Diff line number	Diff line
		@@ -764,12 +764,17 @@ struct tcp_skb_cb {
		eor:1, /* Is skb MSG_EOR marked? */
		unused:6;
		__u32 ack_seq; /* Sequence number ACK'd */
		union {
		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;
		#endif
		} header; /* For incoming frames */
		} header; /* For incoming skbs */
		};
		};

		#define TCP_SKB_CB(__skb) ((struct tcp_skb_cb *)&((__skb)->cb[0]))