Commit 14e8e0f6 authored by Neal Cardwell's avatar Neal Cardwell Committed by Jakub Kicinski
Browse files

tcp: shrink inet_connection_sock icsk_mtup enabled and probe_size 



This commit shrinks inet_connection_sock by 4 bytes, by shrinking
icsk_mtup.enabled from 32 bits to 1 bit, and shrinking
icsk_mtup.probe_size from s32 to an unsuigned 31 bit field.

This is to save space to compensate for the recent introduction of a
new u32 in inet_connection_sock, icsk_probes_tstamp, in the recent bug
fix commit 9d9b1ee0 ("tcp: fix TCP_USER_TIMEOUT with zero window").

This should not change functionality, since icsk_mtup.enabled is only
ever set to 0 or 1, and icsk_mtup.probe_size can only be either 0
or a positive MTU value returned by tcp_mss_to_mtu()

Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20210129185438.1813237-1-ncardwell.kernel@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 4e146def

include/net/inet_connection_sock.h

+3 −3
Original line number Diff line number Diff line
@@ -120,14 +120,14 @@ struct inet_connection_sock { 
		__u16		  rcv_mss;	 /* MSS used for delayed ACK decisions	   */

	} icsk_ack;

	struct {

		int		  enabled;



		/* Range of MTUs to search */

		int		  search_high;

		int		  search_low;



		/* Information on the current probe. */

		int		  probe_size;

		u32		  probe_size:31,

		/* Is the MTUP feature enabled for this connection? */

				  enabled:1;



		u32		  probe_timestamp;

	} icsk_mtup;