9 files changed, 23 insertions, 48 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index f1f472746e6c..de88c5472bfc 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -632,7 +632,7 @@ struct tcp_congestion_ops {
         /* return slow start threshold (required) */
         u32 (*ssthresh)(struct sock *sk);
         /* lower bound for congestion window (optional) */
-        u32 (*min_cwnd)(struct sock *sk);
+        u32 (*min_cwnd)(const struct sock *sk);
         /* do new cwnd calculation (required) */
         void (*cong_avoid)(struct sock *sk, u32 ack,
                            u32 rtt, u32 in_flight, int good_ack);
@@ -667,7 +667,7 @@ extern struct tcp_congestion_ops tcp_init_congestion_ops;
 extern u32 tcp_reno_ssthresh(struct sock *sk);
 extern void tcp_reno_cong_avoid(struct sock *sk, u32 ack,
                                 u32 rtt, u32 in_flight, int flag);
-extern u32 tcp_reno_min_cwnd(struct sock *sk);
+extern u32 tcp_reno_min_cwnd(const struct sock *sk);
 extern struct tcp_congestion_ops tcp_reno;
 
 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
diff --git a/net/ipv4/tcp_bic.c b/net/ipv4/tcp_bic.c
index 035f2092d73a..b2d9021ad22b 100644
--- a/net/ipv4/tcp_bic.c
+++ b/net/ipv4/tcp_bic.c
@@ -198,12 +198,6 @@ static u32 bictcp_undo_cwnd(struct sock *sk)
         return max(tp->snd_cwnd, ca->last_max_cwnd);
 }
 
-static u32 bictcp_min_cwnd(struct sock *sk)
-{
-        const struct tcp_sock *tp = tcp_sk(sk);
-        return tp->snd_ssthresh;
-}
-
 static void bictcp_state(struct sock *sk, u8 new_state)
 {
         if (new_state == TCP_CA_Loss)
@@ -231,7 +225,6 @@ static struct tcp_congestion_ops bictcp = {
         .cong_avoid     = bictcp_cong_avoid,
         .set_state      = bictcp_state,
         .undo_cwnd      = bictcp_undo_cwnd,
-        .min_cwnd       = bictcp_min_cwnd,
         .pkts_acked     = bictcp_acked,
         .owner          = THIS_MODULE,
         .name           = "bic",
diff --git a/net/ipv4/tcp_compound.c b/net/ipv4/tcp_compound.c
index ec68cb8081c1..bc54f7e9aea9 100644
--- a/net/ipv4/tcp_compound.c
+++ b/net/ipv4/tcp_compound.c
@@ -419,7 +419,6 @@ static struct tcp_congestion_ops tcp_compound = {
         .init           = tcp_compound_init,
         .ssthresh       = tcp_reno_ssthresh,
         .cong_avoid     = tcp_compound_cong_avoid,
-        .min_cwnd       = tcp_reno_min_cwnd,
         .rtt_sample     = tcp_compound_rtt_calc,
         .set_state      = tcp_compound_state,
         .cwnd_event     = tcp_compound_cwnd_event,
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 91c2f41c7f58..857eefc52aab 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -38,7 +38,7 @@ int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
         int ret = 0;
 
         /* all algorithms must implement ssthresh and cong_avoid ops */
-        if (!ca->ssthresh || !ca->cong_avoid || !ca->min_cwnd) {
+        if (!ca->ssthresh || !ca->cong_avoid) {
                 printk(KERN_ERR "TCP %s does not implement required ops\n",
                        ca->name);
                 return -EINVAL;
@@ -251,8 +251,8 @@ u32 tcp_reno_ssthresh(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
 
-/* Lower bound on congestion window. */
-u32 tcp_reno_min_cwnd(struct sock *sk)
+/* Lower bound on congestion window with halving. */
+u32 tcp_reno_min_cwnd(const struct sock *sk)
 {
         const struct tcp_sock *tp = tcp_sk(sk);
         return tp->snd_ssthresh/2;
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c
index 31a4986dfbf7..78b7a6b9e4de 100644
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -325,11 +325,6 @@ static u32 bictcp_undo_cwnd(struct sock *sk)
         return max(tcp_sk(sk)->snd_cwnd, ca->last_max_cwnd);
 }
 
-static u32 bictcp_min_cwnd(struct sock *sk)
-{
-        return tcp_sk(sk)->snd_ssthresh;
-}
-
 static void bictcp_state(struct sock *sk, u8 new_state)
 {
         if (new_state == TCP_CA_Loss)
@@ -357,7 +352,6 @@ static struct tcp_congestion_ops cubictcp = {
         .cong_avoid     = bictcp_cong_avoid,
         .set_state      = bictcp_state,
         .undo_cwnd      = bictcp_undo_cwnd,
-        .min_cwnd       = bictcp_min_cwnd,
         .pkts_acked     = bictcp_acked,
         .owner          = THIS_MODULE,
         .name           = "cubic",
diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 1b2ff53f98ed..3d92c1859267 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -246,14 +246,6 @@ static void htcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt,
         }
 }
 
-/* Lower bound on congestion window. */
-static u32 htcp_min_cwnd(struct sock *sk)
-{
-        const struct tcp_sock *tp = tcp_sk(sk);
-        return tp->snd_ssthresh;
-}
-
-
 static void htcp_init(struct sock *sk)
 {
         struct htcp *ca = inet_csk_ca(sk);
@@ -285,7 +277,6 @@ static void htcp_state(struct sock *sk, u8 new_state)
 static struct tcp_congestion_ops htcp = {
         .init           = htcp_init,
         .ssthresh       = htcp_recalc_ssthresh,
-        .min_cwnd       = htcp_min_cwnd,
         .cong_avoid     = htcp_cong_avoid,
         .set_state      = htcp_state,
         .undo_cwnd      = htcp_cwnd_undo,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6d167889a4b0..e08245bdda3a 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1689,17 +1689,26 @@ static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
         tp->snd_cwnd_stamp = tcp_time_stamp;
 }
 
+/* Lower bound on congestion window is slow start threshold
+ * unless congestion avoidance choice decides to overide it.
+ */
+static inline u32 tcp_cwnd_min(const struct sock *sk)
+{
+        const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops;
+
+        return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh;
+}
+
 /* Decrease cwnd each second ack. */
 static void tcp_cwnd_down(struct sock *sk)
 {
-        const struct inet_connection_sock *icsk = inet_csk(sk);
         struct tcp_sock *tp = tcp_sk(sk);
         int decr = tp->snd_cwnd_cnt + 1;
 
         tp->snd_cwnd_cnt = decr&1;
         decr >>= 1;
 
-        if (decr && tp->snd_cwnd > icsk->icsk_ca_ops->min_cwnd(sk))
+        if (decr && tp->snd_cwnd > tcp_cwnd_min(sk))
                 tp->snd_cwnd -= decr;
 
         tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index 1091671751c4..11b42a7135c1 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -199,17 +199,10 @@ static u32 tcp_veno_ssthresh(struct sock *sk)
                 return max(tp->snd_cwnd >> 1U, 2U);
 }
 
-static u32 tcp_veno_min_cwnd(struct sock * sk)
-{
-        const struct tcp_sock *tp = tcp_sk(sk);
-        return tp->snd_ssthresh;
-}
-
 static struct tcp_congestion_ops tcp_veno = {
         .init           = tcp_veno_init,
         .ssthresh       = tcp_veno_ssthresh,
         .cong_avoid     = tcp_veno_cong_avoid,
-        .min_cwnd       = tcp_veno_min_cwnd,
         .rtt_sample     = tcp_veno_rtt_calc,
         .set_state      = tcp_veno_state,
         .cwnd_event     = tcp_veno_cwnd_event,
diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index 0c340c3756c2..29eb258b6d82 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -162,12 +162,6 @@ static inline u32 westwood_acked_count(struct sock *sk)
         return w->cumul_ack;
 }
 
-static inline u32 westwood_bw_rttmin(const struct sock *sk)
-{
-        const struct tcp_sock *tp = tcp_sk(sk);
-        const struct westwood *w = inet_csk_ca(sk);
-        return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
-}
 
 /*
  * TCP Westwood
@@ -175,9 +169,11 @@ static inline u32 westwood_bw_rttmin(const struct sock *sk)
  * in packets we use mss_cache). Rttmin is guaranteed to be >= 2
  * so avoids ever returning 0.
  */
-static u32 tcp_westwood_cwnd_min(struct sock *sk)
+static u32 tcp_westwood_bw_rttmin(const struct sock *sk)
 {
-        return westwood_bw_rttmin(sk);
+        const struct tcp_sock *tp = tcp_sk(sk);
+        const struct westwood *w = inet_csk_ca(sk);
+        return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
 }
 
 static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
@@ -191,11 +187,11 @@ static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event)
                 break;
 
         case CA_EVENT_COMPLETE_CWR:
-                tp->snd_cwnd = tp->snd_ssthresh = westwood_bw_rttmin(sk);
+                tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
                 break;
 
         case CA_EVENT_FRTO:
-                tp->snd_ssthresh = westwood_bw_rttmin(sk);
+                tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk);
                 break;
 
         case CA_EVENT_SLOW_ACK:
@@ -235,7 +231,7 @@ 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,
+        .min_cwnd       = tcp_westwood_bw_rttmin,
         .cwnd_event     = tcp_westwood_event,
         .get_info       = tcp_westwood_info,
         .pkts_acked     = tcp_westwood_pkts_acked,