int curvecpr_client_connected (struct curvecpr_client *client)
{
struct curvecpr_client_cf *cf = &client->cf;
struct curvecpr_session *s = &client->session;
struct curvecpr_packet_hello p;
/* Copy some data into the session. */
curvecpr_bytes_copy(s->their_extension, cf->their_extension, 16);
curvecpr_bytes_copy(s->their_global_pk, cf->their_global_pk, 32);
/* Generate keys. */
s->my_session_nonce = curvecpr_util_random_mod_n(281474976710656LL);
crypto_box_keypair(s->my_session_pk, s->my_session_sk);
crypto_box_beforenm(s->my_session_their_global_key, s->their_global_pk, s->my_session_sk);
crypto_box_beforenm(s->my_global_their_global_key, s->their_global_pk, cf->my_global_sk);
/* Packet identifier. */
curvecpr_bytes_copy(p.id, "QvnQ5XlH", 8);
/* Extensions. */
curvecpr_bytes_copy(p.server_extension, s->their_extension, 16);
curvecpr_bytes_copy(p.client_extension, cf->my_extension, 16);
/* The client's session-specific public key. */
curvecpr_bytes_copy(p.client_session_pk, s->my_session_pk, 32);
/* A series of zero bytes for padding. */
curvecpr_bytes_copy(p._, _zeros, 64);
/* The encrypted data (again, all zeros). Nonce generation is included. */
{
unsigned char nonce[24];
unsigned char data[96] = { 0 };
/* The nonce for the upcoming encrypted data. */
curvecpr_bytes_copy(nonce, "CurveCP-client-H", 16);
curvecpr_session_next_nonce(s, nonce + 16);
curvecpr_bytes_copy(p.nonce, nonce + 16, 8);
/* Actual encryption. */
crypto_box_afternm(data, _zeros, 96, nonce, s->my_session_their_global_key);
curvecpr_bytes_copy(p.box, data + 16, 80);
}
if (cf->ops.send(client, (const unsigned char *)&p, sizeof(struct curvecpr_packet_hello)))
return -EAGAIN;
return 0;
}
static void _update (struct curvecpr_chicago *chicago, long long rtt_ns)
{
chicago->rtt_latest = rtt_ns;
/* Initialization. */
if (!chicago->rtt_average) {
chicago->wr_rate = chicago->rtt_latest;
chicago->rtt_average = chicago->rtt_latest;
chicago->rtt_deviation = chicago->rtt_latest / 2;
chicago->rtt_highwater = chicago->rtt_latest;
chicago->rtt_lowwater = chicago->rtt_latest;
}
/* Jacobson's retransmission timeout calculation. */
long long rtt_delta = chicago->rtt_latest - chicago->rtt_average;
chicago->rtt_average += rtt_delta / 8;
if (rtt_delta < 0)
rtt_delta = -rtt_delta;
rtt_delta -= chicago->rtt_deviation;
chicago->rtt_deviation += rtt_delta / 4;
chicago->rtt_timeout = chicago->rtt_average + 4 * chicago->rtt_deviation;
/* Adjust for delayed acknowledgements with anti-spiking. */
chicago->rtt_timeout += 8 * chicago->wr_rate;
/* Recognize top and bottom of congestion cycle. */
rtt_delta = chicago->rtt_latest - chicago->rtt_highwater;
chicago->rtt_highwater += rtt_delta / 1024;
rtt_delta = chicago->rtt_latest - chicago->rtt_lowwater;
if (rtt_delta > 0)
chicago->rtt_lowwater += rtt_delta / 8192;
else
chicago->rtt_lowwater += rtt_delta / 256;
if (chicago->rtt_average > chicago->rtt_highwater + 5000000)
chicago->seen_recent_high = 1;
else if (chicago->rtt_average < chicago->rtt_lowwater)
chicago->seen_recent_low = 1;
/* Should we update? Only after we've seen ~16 packets. */
if (chicago->clock >= chicago->ns_last_update + 16 * chicago->wr_rate) {
/* Maybe it's been too long (bad timeout -- 10 seconds)... */
if (chicago->clock - chicago->ns_last_update > 10000000000LL) {
chicago->wr_rate = 1000000000;
chicago->wr_rate += curvecpr_util_random_mod_n(chicago->wr_rate / 8);
}
chicago->ns_last_update = chicago->clock;
if (chicago->wr_rate >= 131072) {
/* Additive increase: adjust 1/N by a constant c.
*
* RTT-fair additive increase: adjust 1/N by a constant c every N
* nanoseconds.
*
* Approximation: adjust 1/N by cN every N nanoseconds (i.e.,
* N <- 1/(1/N + cN) = N/(1 + cN^2) every N nanoseconds).
*/
if (chicago->wr_rate < 16777216) {
/* N/(1 + cN^2) ~= N - cN^3 */
long long u = chicago->wr_rate / 131072;
chicago->wr_rate -= u * u * u;
} else {
double d = chicago->wr_rate;
chicago->wr_rate = d / (1 + d * d / 2251799813685248.0);
}
}
if (chicago->rtt_phase == 0) {
if (chicago->seen_older_high) {
chicago->rtt_phase = 1;
chicago->ns_last_edge = chicago->clock;
chicago->wr_rate += curvecpr_util_random_mod_n(chicago->wr_rate / 4);
}
} else {
if (chicago->seen_older_low)
chicago->rtt_phase = 0;
}
chicago->seen_older_high = chicago->seen_recent_high;
chicago->seen_older_low = chicago->seen_recent_low;
chicago->seen_recent_high = 0;
chicago->seen_recent_low = 0;
_try_update_rates(chicago);
}
}