@@ -102,6 +102,7 @@ struct bictcp {
u32 end_seq; /* end_seq of the round */
u32 last_ack; /* last time when the ACK spacing is close */
u32 curr_rtt; /* the minimum rtt of current round */
+ u32 cwnd_prior; /* cwnd before a loss event */
};
static inline void bictcp_reset(struct bictcp *ca)
@@ -305,7 +306,10 @@ static inline void bictcp_update(struct bictcp *ca, u32 cwnd, u32 acked)
if (tcp_friendliness) {
u32 scale = beta_scale;
- delta = (cwnd * scale) >> 3;
+ if (cwnd < ca->cwnd_prior)
+ delta = (cwnd * scale) >> 3; /* CUBIC additive increment */
+ else
+ delta = cwnd; /* Reno additive increment */
while (ca->ack_cnt > delta) { /* update tcp cwnd */
ca->ack_cnt -= delta;
ca->tcp_cwnd++;
@@ -355,6 +359,7 @@ __bpf_kfunc static u32 cubictcp_recalc_ssthresh(struct sock *sk)
/ (2 * BICTCP_BETA_SCALE);
else
ca->last_max_cwnd = tcp_snd_cwnd(tp);
+ ca->cwnd_prior = tcp_snd_cwnd(tp);
return max((tcp_snd_cwnd(tp) * beta) / BICTCP_BETA_SCALE, 2U);
}
Add new field 'cwnd_prior' in bictcp for cwnd before a loss event Suggested by Neal Cardwell https://lore.kernel.org/netdev/c3774057-ee75-4a47-8d09-a4575aa42584@gmail.com/T/#t The original code follows RFC 8312 (obsoleted CUBIC RFC). The patched code follows RFC 9438 (new CUBIC RFC). "Once _W_est_ has grown to reach the _cwnd_ at the time of most recently setting _ssthresh_ -- that is, _W_est_ >= _cwnd_prior_ -- the sender SHOULD set α__cubic_ to 1 to ensure that it can achieve the same congestion window increment rate as Reno, which uses AIMD (1,0.5)." Thanks Mingrui, and Lisong Fixes: 42da09fdf2bb ("tcp_cubic: fix to match Reno additive increment") Signed-off-by: Mingrui Zhang <mrzhang97@gmail.com> Signed-off-by: Lisong Xu <xu@unl.edu> --- net/ipv4/tcp_cubic.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)