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>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 24ec804..4775a1b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -765,11 +765,16 @@
unused:6;
__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]))