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dccp tfrc: Let dccp_tfrc_lib do the sampling work 

This migrates more TFRC-related code into the dccp_tfrc_lib:
 * sampling of the packet size `s' (which is only needed until the first
   loss interval is computed (ccid3_first_li));
 * updating the byte-counter `bytes_recvd' in between sending feedbacks.
The result is a better separation of CCID-3 specific and TFRC specific
code, which aids future integration with ECN and e.g. CCID-4.

Further changes:
----------------
 * replaced magic number of 536 with equivalent constant TCP_MIN_RCVMSS;
   (this constant is also used when no estimate for `s' is available).

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This commit is contained in:
Gerrit Renker 2008-09-04 07:30:19 +02:00
parent 3ca7aea041
commit 34a081be8e
5 changed files with 35 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
net/dccp/ccids/ccid3.c
View File

@ -590,12 +590,9 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
* would bring X down to s/t_mbi. That is why we return
* X_recv according to rfc3448bis-06 for the moment.
*/
u32 rtt = hcrx->rtt ? : DCCP_FALLBACK_RTT, s = hcrx->s;
u32 rtt = hcrx->rtt ? : DCCP_FALLBACK_RTT,
s = tfrc_rx_hist_packet_size(&hcrx->hist);
if (s == 0) {
DCCP_WARN("No sample for s, using fallback\n");
s = TCP_MIN_RCVMSS;
}
hcrx->x_recv = scaled_div32(s, 2 * rtt);
break;
}
@ -617,7 +614,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
if (delta <= 0)
DCCP_BUG("delta (%ld) <= 0", (long)delta);
else
hcrx->x_recv = scaled_div32(hcrx->bytes_recv, delta);
hcrx->x_recv = scaled_div32(hcrx->hist.bytes_recvd, delta);
break;
default:
return;
@ -628,7 +625,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
hcrx->tstamp_last_feedback = now;
hcrx->last_counter = dccp_hdr(skb)->dccph_ccval;
hcrx->bytes_recv = 0;
hcrx->hist.bytes_recvd = 0;
dp->dccps_hc_rx_insert_options = 1;
dccp_send_ack(sk);
@ -669,7 +666,8 @@ static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
static u32 ccid3_first_li(struct sock *sk)
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
u32 x_recv, p, delta;
u32 x_recv, p, delta,
s = tfrc_rx_hist_packet_size(&hcrx->hist);
u64 fval;
/*
@ -686,7 +684,7 @@ static u32 ccid3_first_li(struct sock *sk)
}
delta = ktime_to_us(net_timedelta(hcrx->tstamp_last_feedback));
x_recv = scaled_div32(hcrx->bytes_recv, delta);
x_recv = scaled_div32(hcrx->hist.bytes_recvd, delta);
if (x_recv == 0) { /* would also trigger divide-by-zero */
DCCP_WARN("X_recv==0\n");
if (hcrx->x_recv == 0) {
@ -696,8 +694,7 @@ static u32 ccid3_first_li(struct sock *sk)
x_recv = hcrx->x_recv;
}
fval = scaled_div(hcrx->s, hcrx->rtt);
fval = scaled_div32(fval, x_recv);
fval = scaled_div32(scaled_div(s, hcrx->rtt), x_recv);
p = tfrc_calc_x_reverse_lookup(fval);
ccid3_pr_debug("%s(%p), receive rate=%u bytes/s, implied "
@ -724,31 +721,12 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
if (unlikely(hcrx->state == TFRC_RSTATE_NO_DATA)) {
if (is_data_packet) {
const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
do_feedback = CCID3_FBACK_INITIAL;
ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
hcrx->s = payload;
/*
* Not necessary to update bytes_recv here,
* since X_recv = 0 for the first feedback packet (cf.
* RFC 3448, 6.3) -- gerrit
*/
}
goto update_records;
}
if (tfrc_rx_hist_duplicate(&hcrx->hist, skb))
return; /* done receiving */
if (is_data_packet) {
const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
/*
* Update moving-average of s and the sum of received payload bytes
*/
hcrx->s = tfrc_ewma(hcrx->s, payload, 9);
hcrx->bytes_recv += payload;
}
if (tfrc_rx_hist_loss_pending(&hcrx->hist))
return; /* done receiving */

4
net/dccp/ccids/ccid3.h
View File

@ -124,25 +124,21 @@ enum ccid3_hc_rx_states {
*
* @last_counter - Tracks window counter (RFC 4342, 8.1)
* @state - Receiver state, one of %ccid3_hc_rx_states
* @bytes_recv - Total sum of DCCP payload bytes
* @x_recv - Receiver estimate of send rate (RFC 3448, sec. 4.3)
* @rtt - Receiver estimate of RTT
* @tstamp_last_feedback - Time at which last feedback was sent
* @hist - Packet history (loss detection + RTT sampling)
* @li_hist - Loss Interval database
* @s - Received packet size in bytes
* @p_inverse - Inverse of Loss Event Rate (RFC 4342, sec. 8.5)
*/
struct ccid3_hc_rx_sock {
u8 last_counter:4;
enum ccid3_hc_rx_states state:8;
u32 bytes_recv;
u32 x_recv;
u32 rtt;
ktime_t tstamp_last_feedback;
struct tfrc_rx_hist hist;
struct tfrc_loss_hist li_hist;
u16 s;
#define p_inverse li_hist.i_mean
};

10
net/dccp/ccids/lib/packet_history.c
View File

@ -352,6 +352,16 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
__three_after_loss(h);
}
/*
* Update moving-average of `s' and the sum of received payload bytes.
*/
if (dccp_data_packet(skb)) {
const u32 payload = skb->len - dccp_hdr(skb)->dccph_doff * 4;
h->packet_size = tfrc_ewma(h->packet_size, payload, 9);
h->bytes_recvd += payload;
}
/* RFC 3448, 6.1: update I_0, whose growth implies p <= p_prev */
if (!is_new_loss)
tfrc_lh_update_i_mean(lh, skb);

16
net/dccp/ccids/lib/packet_history.h
View File

@ -91,12 +91,16 @@ struct tfrc_rx_hist_entry {
* @loss_count: Number of entries in circular history
* @loss_start: Movable index (for loss detection)
* @rtt_sample_prev: Used during RTT sampling, points to candidate entry
* @packet_size: Packet size in bytes (as per RFC 3448, 3.1)
* @bytes_recvd: Number of bytes received since last sending feedback
*/
struct tfrc_rx_hist {
struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
u8 loss_count:2,
loss_start:2;
#define rtt_sample_prev loss_start
u32 packet_size,
bytes_recvd;
};
/**
@ -140,6 +144,18 @@ static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
return h->loss_count > 0;
}
/*
* Accessor functions to retrieve parameters sampled by the RX history
*/
static inline u32 tfrc_rx_hist_packet_size(const struct tfrc_rx_hist *h)
{
if (h->packet_size == 0) {
DCCP_WARN("No sample for s, using fallback\n");
return TCP_MIN_RCVMSS;
}
return h->packet_size;
}
extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
const struct sk_buff *skb, const u64 ndp);

2
net/dccp/proto.c
View File

@ -185,7 +185,7 @@ int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
sk->sk_state = DCCP_CLOSED;
sk->sk_write_space = dccp_write_space;
icsk->icsk_sync_mss = dccp_sync_mss;
dp->dccps_mss_cache = 536;
dp->dccps_mss_cache = TCP_MIN_RCVMSS;
dp->dccps_rate_last = jiffies;
dp->dccps_role = DCCP_ROLE_UNDEFINED;
dp->dccps_service = DCCP_SERVICE_CODE_IS_ABSENT;