[lwip-devel] [task #14128] Appropriate byte counting/stretch ACK support

[Joel Cunningham]

Follow-up Comment #6, task #14128 (project lwip):

Here's what Linux's tcp_cong.c is doing:


/* Slow start is used when congestion window is no greater than the slow
start
 * threshold. We base on RFC2581 and also handle stretch ACKs properly.
 * We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but
 * something better;) a packet is only considered (s)acked in its entirety to
 * defend the ACK attacks described in the RFC. Slow start processes a
stretch
 * ACK of degree N as if N acks of degree 1 are received back to back except
 * ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and
 * returns the leftover acks to adjust cwnd in congestion avoidance mode.
 */
u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
{
        u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);

        acked -= cwnd - tp->snd_cwnd;
        tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);

        return acked;
}
EXPORT_SYMBOL_GPL(tcp_slow_start);


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