tcp: consolidate congestion control undo functions

Most TCP congestion controls are using identical logic to undo
cwnd except BBR. This patch consolidates these similar functions
to the one used currently by Reno and others.

Suggested-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

9 files changed, 9 insertions, 103 deletions

diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index 609965f0e298..fc3614377413 100644
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -49,7 +49,6 @@ MODULE_PARM_DESC(smooth_part, "log(B/(B*Smin))/log(B/(B-1))+B, # of RTT from Wma
 struct bictcp {
         u32     cnt;            /* increase cwnd by 1 after ACKs */
         u32     last_max_cwnd;  /* last maximum snd_cwnd */
-        u32     loss_cwnd;      /* congestion window at last loss */
         u32     last_cwnd;      /* the last snd_cwnd */
         u32     last_time;      /* time when updated last_cwnd */
         u32     epoch_start;    /* beginning of an epoch */
@@ -72,7 +71,6 @@ static void bictcp_init(struct sock *sk)
         struct bictcp *ca = inet_csk_ca(sk);
 
         bictcp_reset(ca);
-        ca->loss_cwnd = 0;
 
         if (initial_ssthresh)
                 tcp_sk(sk)->snd_ssthresh = initial_ssthresh;
@@ -172,22 +170,12 @@ static u32 bictcp_recalc_ssthresh(struct sock *sk)
         else
                 ca->last_max_cwnd = tp->snd_cwnd;
 
-        ca->loss_cwnd = tp->snd_cwnd;
-
         if (tp->snd_cwnd <= low_window)
                 return max(tp->snd_cwnd >> 1U, 2U);
         else
                 return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
 }
 
-static u32 bictcp_undo_cwnd(struct sock *sk)
-{
-        const struct tcp_sock *tp = tcp_sk(sk);
-        const struct bictcp *ca = inet_csk_ca(sk);
-
-        return max(tp->snd_cwnd, ca->loss_cwnd);
-}
-
 static void bictcp_state(struct sock *sk, u8 new_state)
 {
         if (new_state == TCP_CA_Loss)
@@ -214,7 +202,7 @@ static struct tcp_congestion_ops bictcp __read_mostly = {
         .ssthresh       = bictcp_recalc_ssthresh,
         .cong_avoid     = bictcp_cong_avoid,
         .set_state      = bictcp_state,
-        .undo_cwnd      = bictcp_undo_cwnd,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .pkts_acked     = bictcp_acked,
         .owner          = THIS_MODULE,
         .name           = "bic",
diff --git a/net/ipv4/tcp_cdg.c b/net/ipv4/tcp_cdg.c
index 50a0f3e51d5b..66ac69f7bd19 100644
--- a/net/ipv4/tcp_cdg.c
+++ b/net/ipv4/tcp_cdg.c
@@ -85,7 +85,6 @@ struct cdg {
         u8  state;
         u8  delack;
         u32 rtt_seq;
-        u32 undo_cwnd;
         u32 shadow_wnd;
         u16 backoff_cnt;
         u16 sample_cnt;
@@ -330,8 +329,6 @@ static u32 tcp_cdg_ssthresh(struct sock *sk)
         struct cdg *ca = inet_csk_ca(sk);
         struct tcp_sock *tp = tcp_sk(sk);
 
-        ca->undo_cwnd = tp->snd_cwnd;
-
         if (ca->state == CDG_BACKOFF)
                 return max(2U, (tp->snd_cwnd * min(1024U, backoff_beta)) >> 10);
 
@@ -344,13 +341,6 @@ static u32 tcp_cdg_ssthresh(struct sock *sk)
         return max(2U, tp->snd_cwnd >> 1);
 }
 
-static u32 tcp_cdg_undo_cwnd(struct sock *sk)
-{
-        struct cdg *ca = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, ca->undo_cwnd);
-}
-
 static void tcp_cdg_cwnd_event(struct sock *sk, const enum tcp_ca_event ev)
 {
         struct cdg *ca = inet_csk_ca(sk);
@@ -403,7 +393,7 @@ struct tcp_congestion_ops tcp_cdg __read_mostly = {
         .cong_avoid = tcp_cdg_cong_avoid,
         .cwnd_event = tcp_cdg_cwnd_event,
         .pkts_acked = tcp_cdg_acked,
-        .undo_cwnd = tcp_cdg_undo_cwnd,
+        .undo_cwnd = tcp_reno_undo_cwnd,
         .ssthresh = tcp_cdg_ssthresh,
         .release = tcp_cdg_release,
         .init = tcp_cdg_init,
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 57ae5b5ae643..78bfadfcf342 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -83,7 +83,6 @@ MODULE_PARM_DESC(hystart_ack_delta, "spacing between ack's indicating train (mse
 struct bictcp {
         u32     cnt;            /* increase cwnd by 1 after ACKs */
         u32     last_max_cwnd;  /* last maximum snd_cwnd */
-        u32     loss_cwnd;      /* congestion window at last loss */
         u32     last_cwnd;      /* the last snd_cwnd */
         u32     last_time;      /* time when updated last_cwnd */
         u32     bic_origin_point;/* origin point of bic function */
@@ -142,7 +141,6 @@ static void bictcp_init(struct sock *sk)
         struct bictcp *ca = inet_csk_ca(sk);
 
         bictcp_reset(ca);
-        ca->loss_cwnd = 0;
 
         if (hystart)
                 bictcp_hystart_reset(sk);
@@ -366,18 +364,9 @@ static u32 bictcp_recalc_ssthresh(struct sock *sk)
         else
                 ca->last_max_cwnd = tp->snd_cwnd;
 
-        ca->loss_cwnd = tp->snd_cwnd;
-
         return max((tp->snd_cwnd * beta) / BICTCP_BETA_SCALE, 2U);
 }
 
-static u32 bictcp_undo_cwnd(struct sock *sk)
-{
-        struct bictcp *ca = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
-}
-
 static void bictcp_state(struct sock *sk, u8 new_state)
 {
         if (new_state == TCP_CA_Loss) {
@@ -470,7 +459,7 @@ static struct tcp_congestion_ops cubictcp __read_mostly = {
         .ssthresh       = bictcp_recalc_ssthresh,
         .cong_avoid     = bictcp_cong_avoid,
         .set_state      = bictcp_state,
-        .undo_cwnd      = bictcp_undo_cwnd,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .cwnd_event     = bictcp_cwnd_event,
         .pkts_acked     = bictcp_acked,
         .owner          = THIS_MODULE,
diff --git a/net/ipv4/tcp_highspeed.c b/net/ipv4/tcp_highspeed.c
index 6d9879e93648..d1c33c91eadc 100644
--- a/net/ipv4/tcp_highspeed.c
+++ b/net/ipv4/tcp_highspeed.c
@@ -94,7 +94,6 @@ static const struct hstcp_aimd_val {
 
 struct hstcp {
         u32     ai;
-        u32     loss_cwnd;
 };
 
 static void hstcp_init(struct sock *sk)
@@ -153,22 +152,14 @@ static u32 hstcp_ssthresh(struct sock *sk)
         const struct tcp_sock *tp = tcp_sk(sk);
         struct hstcp *ca = inet_csk_ca(sk);
 
-        ca->loss_cwnd = tp->snd_cwnd;
         /* Do multiplicative decrease */
         return max(tp->snd_cwnd - ((tp->snd_cwnd * hstcp_aimd_vals[ca->ai].md) >> 8), 2U);
 }
 
-static u32 hstcp_cwnd_undo(struct sock *sk)
-{
-        const struct hstcp *ca = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
-}
-
 static struct tcp_congestion_ops tcp_highspeed __read_mostly = {
         .init           = hstcp_init,
         .ssthresh       = hstcp_ssthresh,
-        .undo_cwnd      = hstcp_cwnd_undo,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .cong_avoid     = hstcp_cong_avoid,
 
         .owner          = THIS_MODULE,
diff --git a/net/ipv4/tcp_illinois.c b/net/ipv4/tcp_illinois.c
index 60352ff4f5a8..7c843578f233 100644
--- a/net/ipv4/tcp_illinois.c
+++ b/net/ipv4/tcp_illinois.c
@@ -48,7 +48,6 @@ struct illinois {
         u32     end_seq;        /* right edge of current RTT */
         u32     alpha;          /* Additive increase */
         u32     beta;           /* Muliplicative decrease */
-        u32     loss_cwnd;      /* cwnd on loss */
         u16     acked;          /* # packets acked by current ACK */
         u8      rtt_above;      /* average rtt has gone above threshold */
         u8      rtt_low;        /* # of rtts measurements below threshold */
@@ -297,18 +296,10 @@ static u32 tcp_illinois_ssthresh(struct sock *sk)
         struct tcp_sock *tp = tcp_sk(sk);
         struct illinois *ca = inet_csk_ca(sk);
 
-        ca->loss_cwnd = tp->snd_cwnd;
         /* Multiplicative decrease */
         return max(tp->snd_cwnd - ((tp->snd_cwnd * ca->beta) >> BETA_SHIFT), 2U);
 }
 
-static u32 tcp_illinois_cwnd_undo(struct sock *sk)
-{
-        const struct illinois *ca = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
-}
-
 /* Extract info for Tcp socket info provided via netlink. */
 static size_t tcp_illinois_info(struct sock *sk, u32 ext, int *attr,
                                 union tcp_cc_info *info)
@@ -336,7 +327,7 @@ static size_t tcp_illinois_info(struct sock *sk, u32 ext, int *attr,
 static struct tcp_congestion_ops tcp_illinois __read_mostly = {
         .init           = tcp_illinois_init,
         .ssthresh       = tcp_illinois_ssthresh,
-        .undo_cwnd      = tcp_illinois_cwnd_undo,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .cong_avoid     = tcp_illinois_cong_avoid,
         .set_state      = tcp_illinois_state,
         .get_info       = tcp_illinois_info,
diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
index 6d650ed3cb59..1ff73982e28c 100644
--- a/net/ipv4/tcp_nv.c
+++ b/net/ipv4/tcp_nv.c
@@ -86,7 +86,6 @@ struct tcpnv {
                                  * < 0 => less than 1 packet/RTT */
         u8  available8;
         u16 available16;
-        u32 loss_cwnd;  /* cwnd at last loss */
         u8  nv_allow_cwnd_growth:1, /* whether cwnd can grow */
                 nv_reset:1,         /* whether to reset values */
                 nv_catchup:1;       /* whether we are growing because
@@ -121,7 +120,6 @@ static inline void tcpnv_reset(struct tcpnv *ca, struct sock *sk)
         struct tcp_sock *tp = tcp_sk(sk);
 
         ca->nv_reset = 0;
-        ca->loss_cwnd = 0;
         ca->nv_no_cong_cnt = 0;
         ca->nv_rtt_cnt = 0;
         ca->nv_last_rtt = 0;
@@ -177,19 +175,10 @@ static void tcpnv_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 static u32 tcpnv_recalc_ssthresh(struct sock *sk)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
-        struct tcpnv *ca = inet_csk_ca(sk);
 
-        ca->loss_cwnd = tp->snd_cwnd;
         return max((tp->snd_cwnd * nv_loss_dec_factor) >> 10, 2U);
 }
 
-static u32 tcpnv_undo_cwnd(struct sock *sk)
-{
-        struct tcpnv *ca = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
-}
-
 static void tcpnv_state(struct sock *sk, u8 new_state)
 {
         struct tcpnv *ca = inet_csk_ca(sk);
@@ -446,7 +435,7 @@ static struct tcp_congestion_ops tcpnv __read_mostly = {
         .ssthresh       = tcpnv_recalc_ssthresh,
         .cong_avoid     = tcpnv_cong_avoid,
         .set_state      = tcpnv_state,
-        .undo_cwnd      = tcpnv_undo_cwnd,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .pkts_acked     = tcpnv_acked,
         .get_info       = tcpnv_get_info,
 
diff --git a/net/ipv4/tcp_scalable.c b/net/ipv4/tcp_scalable.c
index f2123075ce6e..addc122f8818 100644
--- a/net/ipv4/tcp_scalable.c
+++ b/net/ipv4/tcp_scalable.c
@@ -15,10 +15,6 @@
 #define TCP_SCALABLE_AI_CNT     50U
 #define TCP_SCALABLE_MD_SCALE   3
 
-struct scalable {
-        u32 loss_cwnd;
-};
-
 static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 {
         struct tcp_sock *tp = tcp_sk(sk);
@@ -36,23 +32,13 @@ static void tcp_scalable_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 static u32 tcp_scalable_ssthresh(struct sock *sk)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
-        struct scalable *ca = inet_csk_ca(sk);
-
-        ca->loss_cwnd = tp->snd_cwnd;
 
         return max(tp->snd_cwnd - (tp->snd_cwnd>>TCP_SCALABLE_MD_SCALE), 2U);
 }
 
-static u32 tcp_scalable_cwnd_undo(struct sock *sk)
-{
-        const struct scalable *ca = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, ca->loss_cwnd);
-}
-
 static struct tcp_congestion_ops tcp_scalable __read_mostly = {
         .ssthresh       = tcp_scalable_ssthresh,
-        .undo_cwnd      = tcp_scalable_cwnd_undo,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .cong_avoid     = tcp_scalable_cong_avoid,
 
         .owner          = THIS_MODULE,
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index 76005d4b8dfc..6fcf482d611b 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -30,7 +30,6 @@ struct veno {
         u32 basertt;            /* the min of all Veno rtt measurements seen (in usec) */
         u32 inc;                /* decide whether to increase cwnd */
         u32 diff;               /* calculate the diff rate */
-        u32 loss_cwnd;          /* cwnd when loss occured */
 };
 
 /* There are several situations when we must "re-start" Veno:
@@ -194,7 +193,6 @@ static u32 tcp_veno_ssthresh(struct sock *sk)
         const struct tcp_sock *tp = tcp_sk(sk);
         struct veno *veno = inet_csk_ca(sk);
 
-        veno->loss_cwnd = tp->snd_cwnd;
         if (veno->diff < beta)
                 /* in "non-congestive state", cut cwnd by 1/5 */
                 return max(tp->snd_cwnd * 4 / 5, 2U);
@@ -203,17 +201,10 @@ static u32 tcp_veno_ssthresh(struct sock *sk)
                 return max(tp->snd_cwnd >> 1U, 2U);
 }
 
-static u32 tcp_veno_cwnd_undo(struct sock *sk)
-{
-        const struct veno *veno = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, veno->loss_cwnd);
-}
-
 static struct tcp_congestion_ops tcp_veno __read_mostly = {
         .init           = tcp_veno_init,
         .ssthresh       = tcp_veno_ssthresh,
-        .undo_cwnd      = tcp_veno_cwnd_undo,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .cong_avoid     = tcp_veno_cong_avoid,
         .pkts_acked     = tcp_veno_pkts_acked,
         .set_state      = tcp_veno_state,
diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c
index e6ff99c4bd3b..96e829b2e2fc 100644
--- a/net/ipv4/tcp_yeah.c
+++ b/net/ipv4/tcp_yeah.c
@@ -37,7 +37,6 @@ struct yeah {
         u32 fast_count;
 
         u32 pkts_acked;
-        u32 loss_cwnd;
 };
 
 static void tcp_yeah_init(struct sock *sk)
@@ -220,22 +219,14 @@ static u32 tcp_yeah_ssthresh(struct sock *sk)
 
         yeah->fast_count = 0;
         yeah->reno_count = max(yeah->reno_count>>1, 2U);
-        yeah->loss_cwnd = tp->snd_cwnd;
 
         return max_t(int, tp->snd_cwnd - reduction, 2);
 }
 
-static u32 tcp_yeah_cwnd_undo(struct sock *sk)
-{
-        const struct yeah *yeah = inet_csk_ca(sk);
-
-        return max(tcp_sk(sk)->snd_cwnd, yeah->loss_cwnd);
-}
-
 static struct tcp_congestion_ops tcp_yeah __read_mostly = {
         .init           = tcp_yeah_init,
         .ssthresh       = tcp_yeah_ssthresh,
-        .undo_cwnd      = tcp_yeah_cwnd_undo,
+        .undo_cwnd      = tcp_reno_undo_cwnd,
         .cong_avoid     = tcp_yeah_cong_avoid,
         .set_state      = tcp_vegas_state,
         .cwnd_event     = tcp_vegas_cwnd_event,