| /* |
| * TCP Westwood+ |
| * |
| * Angelo Dell'Aera: TCP Westwood+ support |
| */ |
| |
| #include <linux/config.h> |
| #include <linux/mm.h> |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <linux/tcp_diag.h> |
| #include <net/tcp.h> |
| |
| /* TCP Westwood structure */ |
| struct westwood { |
| 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 */ |
| }; |
| |
| |
| /* TCP Westwood functions and constants */ |
| #define TCP_WESTWOOD_RTT_MIN (HZ/20) /* 50ms */ |
| #define TCP_WESTWOOD_INIT_RTT (20*HZ) /* maybe too conservative?! */ |
| |
| /* |
| * @tcp_westwood_create |
| * This function initializes fields used in TCP Westwood+, |
| * it is called after the initial SYN, so the sequence numbers |
| * are correct but new passive connections we have no |
| * information about RTTmin at this time so we simply set it to |
| * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative |
| * since in this way we're sure it will be updated in a consistent |
| * way as soon as possible. It will reasonably happen within the first |
| * RTT period of the connection lifetime. |
| */ |
| static void tcp_westwood_init(struct tcp_sock *tp) |
| { |
| struct westwood *w = tcp_ca(tp); |
| |
| w->bk = 0; |
| w->bw_ns_est = 0; |
| w->bw_est = 0; |
| w->accounted = 0; |
| w->cumul_ack = 0; |
| w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT; |
| w->rtt_win_sx = tcp_time_stamp; |
| w->snd_una = tp->snd_una; |
| } |
| |
| /* |
| * @westwood_do_filter |
| * Low-pass filter. Implemented using constant coefficients. |
| */ |
| static inline u32 westwood_do_filter(u32 a, u32 b) |
| { |
| return (((7 * a) + b) >> 3); |
| } |
| |
| static inline void westwood_filter(struct westwood *w, u32 delta) |
| { |
| w->bw_ns_est = westwood_do_filter(w->bw_ns_est, w->bk / delta); |
| w->bw_est = westwood_do_filter(w->bw_est, w->bw_ns_est); |
| } |
| |
| /* |
| * @westwood_pkts_acked |
| * Called after processing group of packets. |
| * but all westwood needs is the last sample of srtt. |
| */ |
| static void tcp_westwood_pkts_acked(struct tcp_sock *tp, u32 cnt) |
| { |
| struct westwood *w = tcp_ca(tp); |
| if (cnt > 0) |
| w->rtt = tp->srtt >> 3; |
| } |
| |
| /* |
| * @westwood_update_window |
| * It updates RTT evaluation window if it is the right moment to do |
| * it. If so it calls filter for evaluating bandwidth. |
| */ |
| static void westwood_update_window(struct tcp_sock *tp) |
| { |
| struct westwood *w = tcp_ca(tp); |
| s32 delta = tcp_time_stamp - w->rtt_win_sx; |
| |
| /* |
| * See if a RTT-window has passed. |
| * Be careful since if RTT is less than |
| * 50ms we don't filter but we continue 'building the sample'. |
| * This minimum limit was chosen since an estimation on small |
| * time intervals is better to avoid... |
| * Obviously on a LAN we reasonably will always have |
| * right_bound = left_bound + WESTWOOD_RTT_MIN |
| */ |
| if (w->rtt && delta > max_t(u32, w->rtt, TCP_WESTWOOD_RTT_MIN)) { |
| westwood_filter(w, delta); |
| |
| w->bk = 0; |
| w->rtt_win_sx = tcp_time_stamp; |
| } |
| } |
| |
| /* |
| * @westwood_fast_bw |
| * It is called when we are in fast path. In particular it is called when |
| * header prediction is successful. In such case in fact update is |
| * straight forward and doesn't need any particular care. |
| */ |
| static inline void westwood_fast_bw(struct tcp_sock *tp) |
| { |
| struct westwood *w = tcp_ca(tp); |
| |
| westwood_update_window(tp); |
| |
| w->bk += tp->snd_una - w->snd_una; |
| w->snd_una = tp->snd_una; |
| w->rtt_min = min(w->rtt, w->rtt_min); |
| } |
| |
| /* |
| * @westwood_acked_count |
| * This function evaluates cumul_ack for evaluating bk in case of |
| * delayed or partial acks. |
| */ |
| static inline u32 westwood_acked_count(struct tcp_sock *tp) |
| { |
| struct westwood *w = tcp_ca(tp); |
| |
| w->cumul_ack = tp->snd_una - w->snd_una; |
| |
| /* If cumul_ack is 0 this is a dupack since it's not moving |
| * tp->snd_una. |
| */ |
| if (!w->cumul_ack) { |
| w->accounted += tp->mss_cache; |
| w->cumul_ack = tp->mss_cache; |
| } |
| |
| if (w->cumul_ack > tp->mss_cache) { |
| /* Partial or delayed ack */ |
| if (w->accounted >= w->cumul_ack) { |
| w->accounted -= w->cumul_ack; |
| w->cumul_ack = tp->mss_cache; |
| } else { |
| w->cumul_ack -= w->accounted; |
| w->accounted = 0; |
| } |
| } |
| |
| w->snd_una = tp->snd_una; |
| |
| return w->cumul_ack; |
| } |
| |
| static inline u32 westwood_bw_rttmin(const struct tcp_sock *tp) |
| { |
| struct westwood *w = tcp_ca(tp); |
| return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2); |
| } |
| |
| /* |
| * TCP Westwood |
| * Here limit is evaluated as Bw estimation*RTTmin (for obtaining it |
| * in packets we use mss_cache). Rttmin is guaranteed to be >= 2 |
| * so avoids ever returning 0. |
| */ |
| static u32 tcp_westwood_cwnd_min(struct tcp_sock *tp) |
| { |
| return westwood_bw_rttmin(tp); |
| } |
| |
| static void tcp_westwood_event(struct tcp_sock *tp, enum tcp_ca_event event) |
| { |
| struct westwood *w = tcp_ca(tp); |
| |
| switch(event) { |
| case CA_EVENT_FAST_ACK: |
| westwood_fast_bw(tp); |
| break; |
| |
| case CA_EVENT_COMPLETE_CWR: |
| tp->snd_cwnd = tp->snd_ssthresh = westwood_bw_rttmin(tp); |
| break; |
| |
| case CA_EVENT_FRTO: |
| tp->snd_ssthresh = westwood_bw_rttmin(tp); |
| break; |
| |
| case CA_EVENT_SLOW_ACK: |
| westwood_update_window(tp); |
| w->bk += westwood_acked_count(tp); |
| w->rtt_min = min(w->rtt, w->rtt_min); |
| break; |
| |
| default: |
| /* don't care */ |
| break; |
| } |
| } |
| |
| |
| /* Extract info for Tcp socket info provided via netlink. */ |
| static void tcp_westwood_info(struct tcp_sock *tp, u32 ext, |
| struct sk_buff *skb) |
| { |
| const struct westwood *ca = tcp_ca(tp); |
| if (ext & (1<<(TCPDIAG_VEGASINFO-1))) { |
| struct rtattr *rta; |
| struct tcpvegas_info *info; |
| |
| rta = __RTA_PUT(skb, TCPDIAG_VEGASINFO, sizeof(*info)); |
| info = RTA_DATA(rta); |
| info->tcpv_enabled = 1; |
| info->tcpv_rttcnt = 0; |
| info->tcpv_rtt = jiffies_to_usecs(ca->rtt); |
| info->tcpv_minrtt = jiffies_to_usecs(ca->rtt_min); |
| rtattr_failure: ; |
| } |
| } |
| |
| |
| static struct tcp_congestion_ops tcp_westwood = { |
| .init = tcp_westwood_init, |
| .ssthresh = tcp_reno_ssthresh, |
| .cong_avoid = tcp_reno_cong_avoid, |
| .min_cwnd = tcp_westwood_cwnd_min, |
| .cwnd_event = tcp_westwood_event, |
| .get_info = tcp_westwood_info, |
| .pkts_acked = tcp_westwood_pkts_acked, |
| |
| .owner = THIS_MODULE, |
| .name = "westwood" |
| }; |
| |
| static int __init tcp_westwood_register(void) |
| { |
| BUG_ON(sizeof(struct westwood) > TCP_CA_PRIV_SIZE); |
| return tcp_register_congestion_control(&tcp_westwood); |
| } |
| |
| static void __exit tcp_westwood_unregister(void) |
| { |
| tcp_unregister_congestion_control(&tcp_westwood); |
| } |
| |
| module_init(tcp_westwood_register); |
| module_exit(tcp_westwood_unregister); |
| |
| MODULE_AUTHOR("Stephen Hemminger, Angelo Dell'Aera"); |
| MODULE_LICENSE("GPL"); |
| MODULE_DESCRIPTION("TCP Westwood+"); |