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Commit 9772efb9 authored by Stephen Hemminger's avatar Stephen Hemminger Committed by David S. Miller
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[TCP]: Appropriate Byte Count support 



This is an updated version of the RFC3465 ABC patch originally
for Linux 2.6.11-rc4 by Yee-Ting Li. ABC is a way of counting
bytes ack'd rather than packets when updating congestion control.

The orignal ABC described in the RFC applied to a Reno style
algorithm. For advanced congestion control there is little
change after leaving slow start.

Signed-off-by: default avatarStephen Hemminger <shemminger@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7faffa1c

Documentation/networking/ip-sysctl.txt

+5 −0
Original line number Diff line number Diff line
@@ -78,6 +78,11 @@ inet_peer_gc_maxtime - INTEGER 


TCP variables: 



tcp_abc - INTEGER

	Controls Appropriate Byte Count defined in RFC3465. If set to

	0 then does congestion avoid once per ack. 1 is conservative

	value, and 2 is more agressive.



tcp_syn_retries - INTEGER

	Number of times initial SYNs for an active TCP connection attempt

	will be retransmitted. Should not be higher than 255. Default value

include/linux/sysctl.h

+1 −0
Original line number Diff line number Diff line
@@ -390,6 +390,7 @@ enum 
	NET_TCP_BIC_BETA=108,

	NET_IPV4_ICMP_ERRORS_USE_INBOUND_IFADDR=109,

	NET_TCP_CONG_CONTROL=110,

	NET_TCP_ABC=111,

};



enum {

include/linux/tcp.h

+1 −0
Original line number Diff line number Diff line
@@ -326,6 +326,7 @@ struct tcp_sock { 
	__u32	snd_up;		/* Urgent pointer		*/



	__u32	total_retrans;	/* Total retransmits for entire connection */

	__u32	bytes_acked;	/* Appropriate Byte Counting - RFC3465 */



	unsigned int		keepalive_time;	  /* time before keep alive takes place */

	unsigned int		keepalive_intvl;  /* time interval between keep alive probes */

include/net/tcp.h

+19 −0
Original line number Diff line number Diff line
@@ -218,6 +218,7 @@ extern int sysctl_tcp_low_latency; 
extern int sysctl_tcp_nometrics_save;

extern int sysctl_tcp_moderate_rcvbuf;

extern int sysctl_tcp_tso_win_divisor;

extern int sysctl_tcp_abc;



extern atomic_t tcp_memory_allocated;

extern atomic_t tcp_sockets_allocated;
@@ -770,6 +771,23 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk) 
 */

static inline void tcp_slow_start(struct tcp_sock *tp)

{

	if (sysctl_tcp_abc) {

		/* RFC3465: Slow Start

		 * TCP sender SHOULD increase cwnd by the number of

		 * previously unacknowledged bytes ACKed by each incoming

		 * acknowledgment, provided the increase is not more than L

		 */

		if (tp->bytes_acked < tp->mss_cache)

			return;



		/* We MAY increase by 2 if discovered delayed ack */

		if (sysctl_tcp_abc > 1 && tp->bytes_acked > 2*tp->mss_cache) {

			if (tp->snd_cwnd < tp->snd_cwnd_clamp)

				tp->snd_cwnd++;

		}

	}

	tp->bytes_acked = 0;



	if (tp->snd_cwnd < tp->snd_cwnd_clamp)

		tp->snd_cwnd++;

}
@@ -804,6 +822,7 @@ static inline void tcp_enter_cwr(struct sock *sk) 
	struct tcp_sock *tp = tcp_sk(sk);



	tp->prior_ssthresh = 0;

	tp->bytes_acked = 0;

	if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {

		__tcp_enter_cwr(sk);

		tcp_set_ca_state(sk, TCP_CA_CWR);

net/ipv4/sysctl_net_ipv4.c

+8 −0
Original line number Diff line number Diff line
@@ -645,6 +645,14 @@ ctl_table ipv4_table[] = { 
		.proc_handler	= &proc_tcp_congestion_control,

		.strategy	= &sysctl_tcp_congestion_control,

	},

	{

		.ctl_name	= NET_TCP_ABC,

		.procname	= "tcp_abc",

		.data		= &sysctl_tcp_abc,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= &proc_dointvec,

	},



	{ .ctl_name = 0 }

};