[TCP]: Add pluggable congestion control algorithm infrastructure.
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>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index f730935b..e427cf3 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -505,25 +505,6 @@
#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
*/
@@ -596,16 +577,7 @@
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;
@@ -1136,6 +1108,80 @@
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
@@ -1155,91 +1201,6 @@
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.
@@ -1288,7 +1249,7 @@
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;
@@ -1876,52 +1837,4 @@
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 */