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[TCP]: Add pluggable congestion control algorithm infrastructure.
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Allow TCP to have multiple pluggable congestion control algorithms.
Algorithms are defined by a set of operations and can be built in
or modules.  The legacy "new RENO" algorithm is used as a starting
point and fallback.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Stephen Hemminger authored and David S. Miller committed Jun 23, 2005
1 parent a8ad86f commit 317a76f
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Showing 13 changed files with 399 additions and 999 deletions.
9 changes: 1 addition & 8 deletions include/linux/sysctl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -333,21 +333,14 @@ enum
NET_TCP_FRTO=92,
NET_TCP_LOW_LATENCY=93,
NET_IPV4_IPFRAG_SECRET_INTERVAL=94,
NET_TCP_WESTWOOD=95,
NET_IPV4_IGMP_MAX_MSF=96,
NET_TCP_NO_METRICS_SAVE=97,
NET_TCP_VEGAS=98,
NET_TCP_VEGAS_ALPHA=99,
NET_TCP_VEGAS_BETA=100,
NET_TCP_VEGAS_GAMMA=101,
NET_TCP_BIC=102,
NET_TCP_BIC_FAST_CONVERGENCE=103,
NET_TCP_BIC_LOW_WINDOW=104,
NET_TCP_DEFAULT_WIN_SCALE=105,
NET_TCP_MODERATE_RCVBUF=106,
NET_TCP_TSO_WIN_DIVISOR=107,
NET_TCP_BIC_BETA=108,
NET_IPV4_ICMP_ERRORS_USE_INBOUND_IFADDR=109,
NET_TCP_CONG_CONTROL=110,
};

enum {
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49 changes: 10 additions & 39 deletions include/linux/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -203,13 +203,6 @@ struct tcp_sack_block {
__u32 end_seq;
};

enum tcp_congestion_algo {
TCP_RENO=0,
TCP_VEGAS,
TCP_WESTWOOD,
TCP_BIC,
};

struct tcp_options_received {
/* PAWS/RTTM data */
long ts_recent_stamp;/* Time we stored ts_recent (for aging) */
Expand Down Expand Up @@ -305,7 +298,7 @@ struct tcp_sock {
__u8 reordering; /* Packet reordering metric. */
__u8 frto_counter; /* Number of new acks after RTO */

__u8 adv_cong; /* Using Vegas, Westwood, or BIC */
__u8 unused;
__u8 defer_accept; /* User waits for some data after accept() */

/* RTT measurement */
Expand Down Expand Up @@ -401,44 +394,22 @@ struct tcp_sock {
__u32 time;
} rcvq_space;

/* TCP Westwood structure */
struct {
__u32 bw_ns_est; /* first bandwidth estimation..not too smoothed 8) */
__u32 bw_est; /* bandwidth estimate */
__u32 rtt_win_sx; /* here starts a new evaluation... */
__u32 bk;
__u32 snd_una; /* used for evaluating the number of acked bytes */
__u32 cumul_ack;
__u32 accounted;
__u32 rtt;
__u32 rtt_min; /* minimum observed RTT */
} westwood;

/* Vegas variables */
struct {
__u32 beg_snd_nxt; /* right edge during last RTT */
__u32 beg_snd_una; /* left edge during last RTT */
__u32 beg_snd_cwnd; /* saves the size of the cwnd */
__u8 doing_vegas_now;/* if true, do vegas for this RTT */
__u16 cntRTT; /* # of RTTs measured within last RTT */
__u32 minRTT; /* min of RTTs measured within last RTT (in usec) */
__u32 baseRTT; /* the min of all Vegas RTT measurements seen (in usec) */
} vegas;

/* BI TCP Parameters */
struct {
__u32 cnt; /* increase cwnd by 1 after this number of ACKs */
__u32 last_max_cwnd; /* last maximium snd_cwnd */
__u32 last_cwnd; /* the last snd_cwnd */
__u32 last_stamp; /* time when updated last_cwnd */
} bictcp;
/* Pluggable TCP congestion control hook */
struct tcp_congestion_ops *ca_ops;
u32 ca_priv[16];
#define TCP_CA_PRIV_SIZE (16*sizeof(u32))
};

static inline struct tcp_sock *tcp_sk(const struct sock *sk)
{
return (struct tcp_sock *)sk;
}

static inline void *tcp_ca(const struct tcp_sock *tp)
{
return (void *) tp->ca_priv;
}

#endif

#endif /* _LINUX_TCP_H */
237 changes: 75 additions & 162 deletions include/net/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -505,25 +505,6 @@ static __inline__ int tcp_sk_listen_hashfn(struct sock *sk)
#else
# define TCP_TW_RECYCLE_TICK (12+2-TCP_TW_RECYCLE_SLOTS_LOG)
#endif

#define BICTCP_BETA_SCALE 1024 /* Scale factor beta calculation
* max_cwnd = snd_cwnd * beta
*/
#define BICTCP_MAX_INCREMENT 32 /*
* Limit on the amount of
* increment allowed during
* binary search.
*/
#define BICTCP_FUNC_OF_MIN_INCR 11 /*
* log(B/Smin)/log(B/(B-1))+1,
* Smin:min increment
* B:log factor
*/
#define BICTCP_B 4 /*
* In binary search,
* go to point (max+min)/N
*/

/*
* TCP option
*/
Expand Down Expand Up @@ -596,16 +577,7 @@ extern int sysctl_tcp_adv_win_scale;
extern int sysctl_tcp_tw_reuse;
extern int sysctl_tcp_frto;
extern int sysctl_tcp_low_latency;
extern int sysctl_tcp_westwood;
extern int sysctl_tcp_vegas_cong_avoid;
extern int sysctl_tcp_vegas_alpha;
extern int sysctl_tcp_vegas_beta;
extern int sysctl_tcp_vegas_gamma;
extern int sysctl_tcp_nometrics_save;
extern int sysctl_tcp_bic;
extern int sysctl_tcp_bic_fast_convergence;
extern int sysctl_tcp_bic_low_window;
extern int sysctl_tcp_bic_beta;
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;

Expand Down Expand Up @@ -1136,6 +1108,80 @@ static inline void tcp_packets_out_dec(struct tcp_sock *tp,
tp->packets_out -= tcp_skb_pcount(skb);
}

/* Events passed to congestion control interface */
enum tcp_ca_event {
CA_EVENT_TX_START, /* first transmit when no packets in flight */
CA_EVENT_CWND_RESTART, /* congestion window restart */
CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */
CA_EVENT_FRTO, /* fast recovery timeout */
CA_EVENT_LOSS, /* loss timeout */
CA_EVENT_FAST_ACK, /* in sequence ack */
CA_EVENT_SLOW_ACK, /* other ack */
};

/*
* Interface for adding new TCP congestion control handlers
*/
#define TCP_CA_NAME_MAX 16
struct tcp_congestion_ops {
struct list_head list;

/* initialize private data (optional) */
void (*init)(struct tcp_sock *tp);
/* cleanup private data (optional) */
void (*release)(struct tcp_sock *tp);

/* return slow start threshold (required) */
u32 (*ssthresh)(struct tcp_sock *tp);
/* lower bound for congestion window (optional) */
u32 (*min_cwnd)(struct tcp_sock *tp);
/* do new cwnd calculation (required) */
void (*cong_avoid)(struct tcp_sock *tp, u32 ack,
u32 rtt, u32 in_flight, int good_ack);
/* round trip time sample per acked packet (optional) */
void (*rtt_sample)(struct tcp_sock *tp, u32 usrtt);
/* call before changing ca_state (optional) */
void (*set_state)(struct tcp_sock *tp, u8 new_state);
/* call when cwnd event occurs (optional) */
void (*cwnd_event)(struct tcp_sock *tp, enum tcp_ca_event ev);
/* new value of cwnd after loss (optional) */
u32 (*undo_cwnd)(struct tcp_sock *tp);
/* hook for packet ack accounting (optional) */
void (*pkts_acked)(struct tcp_sock *tp, u32 num_acked);
/* get info for tcp_diag (optional) */
void (*get_info)(struct tcp_sock *tp, u32 ext, struct sk_buff *skb);

char name[TCP_CA_NAME_MAX];
struct module *owner;
};

extern int tcp_register_congestion_control(struct tcp_congestion_ops *type);
extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);

extern void tcp_init_congestion_control(struct tcp_sock *tp);
extern void tcp_cleanup_congestion_control(struct tcp_sock *tp);
extern int tcp_set_default_congestion_control(const char *name);
extern void tcp_get_default_congestion_control(char *name);

extern struct tcp_congestion_ops tcp_reno;
extern u32 tcp_reno_ssthresh(struct tcp_sock *tp);
extern void tcp_reno_cong_avoid(struct tcp_sock *tp, u32 ack,
u32 rtt, u32 in_flight, int flag);
extern u32 tcp_reno_min_cwnd(struct tcp_sock *tp);

static inline void tcp_set_ca_state(struct tcp_sock *tp, u8 ca_state)
{
if (tp->ca_ops->set_state)
tp->ca_ops->set_state(tp, ca_state);
tp->ca_state = ca_state;
}

static inline void tcp_ca_event(struct tcp_sock *tp, enum tcp_ca_event event)
{
if (tp->ca_ops->cwnd_event)
tp->ca_ops->cwnd_event(tp, event);
}

/* This determines how many packets are "in the network" to the best
* of our knowledge. In many cases it is conservative, but where
* detailed information is available from the receiver (via SACK
Expand All @@ -1155,91 +1201,6 @@ static __inline__ unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
return (tp->packets_out - tp->left_out + tp->retrans_out);
}

/*
* Which congestion algorithim is in use on the connection.
*/
#define tcp_is_vegas(__tp) ((__tp)->adv_cong == TCP_VEGAS)
#define tcp_is_westwood(__tp) ((__tp)->adv_cong == TCP_WESTWOOD)
#define tcp_is_bic(__tp) ((__tp)->adv_cong == TCP_BIC)

/* Recalculate snd_ssthresh, we want to set it to:
*
* Reno:
* one half the current congestion window, but no
* less than two segments
*
* BIC:
* behave like Reno until low_window is reached,
* then increase congestion window slowly
*/
static inline __u32 tcp_recalc_ssthresh(struct tcp_sock *tp)
{
if (tcp_is_bic(tp)) {
if (sysctl_tcp_bic_fast_convergence &&
tp->snd_cwnd < tp->bictcp.last_max_cwnd)
tp->bictcp.last_max_cwnd = (tp->snd_cwnd *
(BICTCP_BETA_SCALE
+ sysctl_tcp_bic_beta))
/ (2 * BICTCP_BETA_SCALE);
else
tp->bictcp.last_max_cwnd = tp->snd_cwnd;

if (tp->snd_cwnd > sysctl_tcp_bic_low_window)
return max((tp->snd_cwnd * sysctl_tcp_bic_beta)
/ BICTCP_BETA_SCALE, 2U);
}

return max(tp->snd_cwnd >> 1U, 2U);
}

/* Stop taking Vegas samples for now. */
#define tcp_vegas_disable(__tp) ((__tp)->vegas.doing_vegas_now = 0)

static inline void tcp_vegas_enable(struct tcp_sock *tp)
{
/* There are several situations when we must "re-start" Vegas:
*
* o when a connection is established
* o after an RTO
* o after fast recovery
* o when we send a packet and there is no outstanding
* unacknowledged data (restarting an idle connection)
*
* In these circumstances we cannot do a Vegas calculation at the
* end of the first RTT, because any calculation we do is using
* stale info -- both the saved cwnd and congestion feedback are
* stale.
*
* Instead we must wait until the completion of an RTT during
* which we actually receive ACKs.
*/

/* Begin taking Vegas samples next time we send something. */
tp->vegas.doing_vegas_now = 1;

/* Set the beginning of the next send window. */
tp->vegas.beg_snd_nxt = tp->snd_nxt;

tp->vegas.cntRTT = 0;
tp->vegas.minRTT = 0x7fffffff;
}

/* Should we be taking Vegas samples right now? */
#define tcp_vegas_enabled(__tp) ((__tp)->vegas.doing_vegas_now)

extern void tcp_ca_init(struct tcp_sock *tp);

static inline void tcp_set_ca_state(struct tcp_sock *tp, u8 ca_state)
{
if (tcp_is_vegas(tp)) {
if (ca_state == TCP_CA_Open)
tcp_vegas_enable(tp);
else
tcp_vegas_disable(tp);
}
tp->ca_state = ca_state;
}

/* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
* The exception is rate halving phase, when cwnd is decreasing towards
* ssthresh.
Expand Down Expand Up @@ -1288,7 +1249,7 @@ static inline void tcp_cwnd_validate(struct sock *sk, struct tcp_sock *tp)
static inline void __tcp_enter_cwr(struct tcp_sock *tp)
{
tp->undo_marker = 0;
tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
tp->snd_ssthresh = tp->ca_ops->ssthresh(tp);
tp->snd_cwnd = min(tp->snd_cwnd,
tcp_packets_in_flight(tp) + 1U);
tp->snd_cwnd_cnt = 0;
Expand Down Expand Up @@ -1876,52 +1837,4 @@ struct tcp_iter_state {
extern int tcp_proc_register(struct tcp_seq_afinfo *afinfo);
extern void tcp_proc_unregister(struct tcp_seq_afinfo *afinfo);

/* TCP Westwood functions and constants */

#define TCP_WESTWOOD_INIT_RTT (20*HZ) /* maybe too conservative?! */
#define TCP_WESTWOOD_RTT_MIN (HZ/20) /* 50ms */

static inline void tcp_westwood_update_rtt(struct tcp_sock *tp, __u32 rtt_seq)
{
if (tcp_is_westwood(tp))
tp->westwood.rtt = rtt_seq;
}

static inline __u32 __tcp_westwood_bw_rttmin(const struct tcp_sock *tp)
{
return max((tp->westwood.bw_est) * (tp->westwood.rtt_min) /
(__u32) (tp->mss_cache_std),
2U);
}

static inline __u32 tcp_westwood_bw_rttmin(const struct tcp_sock *tp)
{
return tcp_is_westwood(tp) ? __tcp_westwood_bw_rttmin(tp) : 0;
}

static inline int tcp_westwood_ssthresh(struct tcp_sock *tp)
{
__u32 ssthresh = 0;

if (tcp_is_westwood(tp)) {
ssthresh = __tcp_westwood_bw_rttmin(tp);
if (ssthresh)
tp->snd_ssthresh = ssthresh;
}

return (ssthresh != 0);
}

static inline int tcp_westwood_cwnd(struct tcp_sock *tp)
{
__u32 cwnd = 0;

if (tcp_is_westwood(tp)) {
cwnd = __tcp_westwood_bw_rttmin(tp);
if (cwnd)
tp->snd_cwnd = cwnd;
}

return (cwnd != 0);
}
#endif /* _TCP_H */
3 changes: 2 additions & 1 deletion net/ipv4/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,8 @@
obj-y := utils.o route.o inetpeer.o protocol.o \
ip_input.o ip_fragment.o ip_forward.o ip_options.o \
ip_output.o ip_sockglue.o \
tcp.o tcp_input.o tcp_output.o tcp_timer.o tcp_ipv4.o tcp_minisocks.o \
tcp.o tcp_input.o tcp_output.o tcp_timer.o tcp_ipv4.o \
tcp_minisocks.o tcp_cong.o \
datagram.o raw.o udp.o arp.o icmp.o devinet.o af_inet.o igmp.o \
sysctl_net_ipv4.o fib_frontend.o fib_semantics.o

Expand Down
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