Commit 713bafea authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

tcp: retire FACK loss detection 



FACK loss detection has been disabled by default and the
successor RACK subsumed FACK and can handle reordering better.
This patch removes FACK to simplify TCP loss recovery.

Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarNeal Cardwell <ncardwell@google.com>
Reviewed-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: default avatarPriyaranjan Jha <priyarjha@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e4ec1384

Documentation/networking/ip-sysctl.txt

+1 −2
Original line number Diff line number Diff line
@@ -289,8 +289,7 @@ tcp_ecn_fallback - BOOLEAN 
	Default: 1 (fallback enabled)



tcp_fack - BOOLEAN

	Enable FACK congestion avoidance and fast retransmission.

	The value is not used, if tcp_sack is not enabled.

	This is a legacy option, it has no effect anymore.



tcp_fin_timeout - INTEGER

	The length of time an orphaned (no longer referenced by any

include/linux/tcp.h

+0 −1
Original line number Diff line number Diff line
@@ -85,7 +85,6 @@ struct tcp_sack_block { 


/*These are used to set the sack_ok field in struct tcp_options_received */

#define TCP_SACK_SEEN     (1 << 0)   /*1 = peer is SACK capable, */

#define TCP_FACK_ENABLED  (1 << 1)   /*1 = FACK is enabled locally*/

#define TCP_DSACK_SEEN    (1 << 2)   /*1 = DSACK was received from peer*/



struct tcp_options_received {

include/net/tcp.h

+1 −13
Original line number Diff line number Diff line
@@ -384,7 +384,6 @@ void tcp_update_metrics(struct sock *sk); 
void tcp_init_metrics(struct sock *sk);

void tcp_metrics_init(void);

bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);

void tcp_disable_fack(struct tcp_sock *tp);

void tcp_close(struct sock *sk, long timeout);

void tcp_init_sock(struct sock *sk);

void tcp_init_transfer(struct sock *sk, int bpf_op);
@@ -776,7 +775,7 @@ struct tcp_skb_cb { 
	};

	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/



	__u8		sacked;		/* State flags for SACK/FACK.	*/

	__u8		sacked;		/* State flags for SACK.	*/

#define TCPCB_SACKED_ACKED	0x01	/* SKB ACK'd by a SACK block	*/

#define TCPCB_SACKED_RETRANS	0x02	/* SKB retransmitted		*/

#define TCPCB_LOST		0x04	/* SKB is lost			*/
@@ -1066,7 +1065,6 @@ void tcp_rate_check_app_limited(struct sock *sk); 
 *

 * tcp_is_sack - SACK enabled

 * tcp_is_reno - No SACK

 * tcp_is_fack - FACK enabled, implies SACK enabled

 */

static inline int tcp_is_sack(const struct tcp_sock *tp)

{
@@ -1078,16 +1076,6 @@ static inline bool tcp_is_reno(const struct tcp_sock *tp) 
	return !tcp_is_sack(tp);

}



static inline bool tcp_is_fack(const struct tcp_sock *tp)

{

	return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;

}



static inline void tcp_enable_fack(struct tcp_sock *tp)

{

	tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;

}



static inline unsigned int tcp_left_out(const struct tcp_sock *tp)

{

	return tp->sacked_out + tp->lost_out;

include/uapi/linux/snmp.h

+0 −1
Original line number Diff line number Diff line
@@ -191,7 +191,6 @@ enum 
	LINUX_MIB_TCPRENORECOVERY,		/* TCPRenoRecovery */

	LINUX_MIB_TCPSACKRECOVERY,		/* TCPSackRecovery */

	LINUX_MIB_TCPSACKRENEGING,		/* TCPSACKReneging */

	LINUX_MIB_TCPFACKREORDER,		/* TCPFACKReorder */

	LINUX_MIB_TCPSACKREORDER,		/* TCPSACKReorder */

	LINUX_MIB_TCPRENOREORDER,		/* TCPRenoReorder */

	LINUX_MIB_TCPTSREORDER,			/* TCPTSReorder */

net/ipv4/proc.c

+0 −1
Original line number Diff line number Diff line
@@ -212,7 +212,6 @@ static const struct snmp_mib snmp4_net_list[] = { 
	SNMP_MIB_ITEM("TCPRenoRecovery", LINUX_MIB_TCPRENORECOVERY),

	SNMP_MIB_ITEM("TCPSackRecovery", LINUX_MIB_TCPSACKRECOVERY),

	SNMP_MIB_ITEM("TCPSACKReneging", LINUX_MIB_TCPSACKRENEGING),

	SNMP_MIB_ITEM("TCPFACKReorder", LINUX_MIB_TCPFACKREORDER),

	SNMP_MIB_ITEM("TCPSACKReorder", LINUX_MIB_TCPSACKREORDER),

	SNMP_MIB_ITEM("TCPRenoReorder", LINUX_MIB_TCPRENOREORDER),

	SNMP_MIB_ITEM("TCPTSReorder", LINUX_MIB_TCPTSREORDER),

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