Line data    Source code

       1             : /* SPDX-License-Identifier: GPL-2.0-or-later */
       2             : /* QUIC kernel implementation
       3             :  * (C) Copyright Red Hat Corp. 2023
       4             :  *
       5             :  * This file is part of the QUIC kernel implementation
       6             :  *
       7             :  * Written or modified by:
       8             :  *    Xin Long <lucien.xin@gmail.com>
       9             :  */
      10             : 
      11             : #define QUIC_KPERSISTENT_CONGESTION_THRESHOLD   3
      12             : #define QUIC_KPACKET_THRESHOLD                  3
      13             : #define QUIC_KTIME_THRESHOLD(rtt)               ((rtt) * 9 / 8)
      14             : #define QUIC_KGRANULARITY                       1000U
      15             : 
      16             : #define QUIC_RTT_INIT           333000U
      17             : #define QUIC_RTT_MAX            2000000U
      18             : #define QUIC_RTT_MIN            QUIC_KGRANULARITY
      19             : 
      20             : /* rfc9002#section-7.3: Congestion Control States
      21             :  *
      22             :  *                  New path or      +------------+
      23             :  *             persistent congestion |   Slow     |
      24             :  *         (O)---------------------->|   Start    |
      25             :  *                                   +------------+
      26             :  *                                         |
      27             :  *                                 Loss or |
      28             :  *                         ECN-CE increase |
      29             :  *                                         v
      30             :  *  +------------+     Loss or       +------------+
      31             :  *  | Congestion |  ECN-CE increase  |  Recovery  |
      32             :  *  | Avoidance  |------------------>|   Period   |
      33             :  *  +------------+                   +------------+
      34             :  *            ^                            |
      35             :  *            |                            |
      36             :  *            +----------------------------+
      37             :  *               Acknowledgment of packet
      38             :  *                 sent during recovery
      39             :  */
      40             : enum quic_cong_state {
      41             :         QUIC_CONG_SLOW_START,
      42             :         QUIC_CONG_RECOVERY_PERIOD,
      43             :         QUIC_CONG_CONGESTION_AVOIDANCE,
      44             : };
      45             : 
      46             : struct quic_cong {
      47             :         /* RTT tracking */
      48             :         u32 smoothed_rtt;       /* Smoothed RTT */
      49             :         u32 latest_rtt;         /* Latest RTT sample */
      50             :         u32 min_rtt;            /* Lowest observed RTT */
      51             :         u32 rttvar;             /* RTT variation */
      52             :         u32 loss_delay;         /* Time before marking loss */
      53             :         u32 pto;                /* Probe timeout */
      54             : 
      55             :         /* Timing & pacing */
      56             :         u32 max_ack_delay;      /* max_ack_delay from rfc9000#section-18.2 */
      57             :         u32 recovery_time;      /* Recovery period start */
      58             :         u32 pacing_rate;        /* Packet sending speed Bytes/sec */
      59             :         u64 pacing_time;        /* Next send time */
      60             :         u32 time;               /* Cached time */
      61             : 
      62             :         /* Congestion window */
      63             :         u32 max_window;         /* Max growth cap */
      64             :         u32 min_window;         /* Min window limit */
      65             :         u32 ssthresh;           /* Slow start threshold */
      66             :         u32 window;             /* Bytes in flight allowed */
      67             :         u32 mss;                /* QUIC MSS (excl. UDP) */
      68             : 
      69             :         /* Algorithm-specific */
      70             :         struct quic_cong_ops *ops;
      71             :         u64 priv[8];            /* Algo private data */
      72             : 
      73             :         /* Flags & state */
      74             :         u8 min_rtt_valid;       /* min_rtt initialized */
      75             :         u8 is_rtt_set;          /* RTT samples exist */
      76             :         u8 state;               /* State machine in rfc9002#section-7.3 */
      77             : };
      78             : 
      79             : /* Hooks for congestion control algorithms */
      80             : struct quic_cong_ops {
      81             :         void (*on_packet_acked)(struct quic_cong *cong, u32 time, u32 bytes, s64 number);
      82             :         void (*on_packet_lost)(struct quic_cong *cong, u32 time, u32 bytes, s64 number);
      83             :         void (*on_process_ecn)(struct quic_cong *cong);
      84             :         void (*on_init)(struct quic_cong *cong);
      85             : 
      86             :         /* Optional callbacks */
      87             :         void (*on_packet_sent)(struct quic_cong *cong, u32 time, u32 bytes, s64 number);
      88             :         void (*on_ack_recv)(struct quic_cong *cong, u32 bytes, u32 max_rate);
      89             :         void (*on_rtt_update)(struct quic_cong *cong);
      90             : };
      91             : 
      92        2916 : static inline void quic_cong_set_mss(struct quic_cong *cong, u32 mss)
      93             : {
      94        2916 :         if (cong->mss == mss)
      95             :                 return;
      96             : 
      97             :         /* rfc9002#section-7.2: Initial and Minimum Congestion Window */
      98        1107 :         cong->mss = mss;
      99        1107 :         cong->min_window = max(min(mss * 10, 14720U), mss * 2);
     100             : 
     101        1107 :         if (cong->window < cong->min_window)
     102        1003 :                 cong->window = cong->min_window;
     103             : }
     104             : 
     105             : static inline void *quic_cong_priv(struct quic_cong *cong)
     106             : {
     107     9440298 :         return (void *)cong->priv;
     108             : }
     109             : 
     110             : void quic_cong_on_packet_acked(struct quic_cong *cong, u32 time, u32 bytes, s64 number);
     111             : void quic_cong_on_packet_lost(struct quic_cong *cong, u32 time, u32 bytes, s64 number);
     112             : void quic_cong_on_process_ecn(struct quic_cong *cong);
     113             : 
     114             : void quic_cong_on_packet_sent(struct quic_cong *cong, u32 time, u32 bytes, s64 number);
     115             : void quic_cong_on_ack_recv(struct quic_cong *cong, u32 bytes, u32 max_rate);
     116             : void quic_cong_rtt_update(struct quic_cong *cong, u32 time, u32 ack_delay);
     117             : 
     118             : void quic_cong_set_srtt(struct quic_cong *cong, u32 srtt);
     119             : void quic_cong_set_algo(struct quic_cong *cong, u8 algo);
     120             : void quic_cong_init(struct quic_cong *cong);