tcp: add cwnd_undo functions to various tcp cc algorithms
congestion control algorithms that do not halve cwnd in their .ssthresh
should provide a .cwnd_undo rather than rely on current fallback which
assumes reno halving (and thus doubles the cwnd).
All of these do 'something else' in their .ssthresh implementation, thus
store the cwnd on loss and provide .undo_cwnd to restore it again.
A followup patch will remove the fallback and all algorithms will
need to provide a .cwnd_undo function.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_yeah.c b/net/ipv4/tcp_yeah.c
index 9c5fc97..e6ff99c 100644
--- a/net/ipv4/tcp_yeah.c
+++ b/net/ipv4/tcp_yeah.c
@@ -37,6 +37,7 @@ struct yeah {
u32 fast_count;
u32 pkts_acked;
+ u32 loss_cwnd;
};
static void tcp_yeah_init(struct sock *sk)
@@ -219,13 +220,22 @@ 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,
.cong_avoid = tcp_yeah_cong_avoid,
.set_state = tcp_vegas_state,
.cwnd_event = tcp_vegas_cwnd_event,