[CCID 3]: History access is redundant when sending feedback
This is a simplification to reduce the number of history accesses: when
receiving a new packet, the receiver needs to access the RX history twice:
* first to create / add a new entry
* then, when sending feedback, the just-created entry must be `found'
via history lookup.
Meaning that, for the same information, it first needs an exclusive
write-access and then a (shared) read access. Without locking in between
these calls, the history information may have already changed.
This patch bypasses the double lookup by directly using the available data
from skb. In addition, some more informative debugging information was added.
(NB: using the `packet' entry from rx_packet_recv() is not a good idea, since this
can interfer with the RX history garbage collection: the entry may be garbage-
collected at the same instant that send_feedback() tries to use it.)
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/ccids/ccid3.c | 35 ++++++++++++++---------------------
1 file changed, 14 insertions(+), 21 deletions(-)
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -745,15 +745,12 @@ static int ccid3_hc_rx_update_p(struct c
return (hcrx->ccid3hcrx_pinv < pinv_prev);
}
-static void ccid3_hc_rx_send_feedback(struct sock *sk)
+static void ccid3_hc_rx_send_feedback(struct sock *sk, struct sk_buff *skb)
{
struct ccid3_hc_rx_sock *hcrx = ccid3_hc_rx_sk(sk);
struct dccp_sock *dp = dccp_sk(sk);
- struct dccp_rx_hist_entry *packet;
- struct timeval now;
- suseconds_t delta;
-
- ccid3_pr_debug("%s(%p) - entry \n", dccp_role(sk), sk);
+ struct timeval now, t_recv;
+ suseconds_t delta = 0;
do_gettimeofday(&now);
@@ -773,23 +770,19 @@ static void ccid3_hc_rx_send_feedback(st
DCCP_BUG("%s(%p) - Illegal state TERM", dccp_role(sk), sk);
return;
}
+ ccid3_pr_debug("Interval %ldusec, X_recv=%u, 1/p=%u\n", (long)delta,
+ hcrx->ccid3hcrx_x_recv, hcrx->ccid3hcrx_pinv);
- packet = dccp_rx_hist_find_data_packet(&hcrx->ccid3hcrx_hist);
- if (unlikely(packet == NULL)) {
- DCCP_WARN("%s(%p), no data packet in history!\n",
- dccp_role(sk), sk);
- return;
- }
+ /* Elapsed time information [RFC 4340, 13.2] in units of 10 * usecs */
+ skb_get_timestamp(skb, &t_recv);
+ delta = timeval_delta(&now, &t_recv);
+ DCCP_BUG_ON(delta < 0);
+ hcrx->ccid3hcrx_elapsed_time = delta / 10;
hcrx->ccid3hcrx_tstamp_last_feedback = now;
- hcrx->ccid3hcrx_ccval_last_counter = packet->dccphrx_ccval;
+ hcrx->ccid3hcrx_ccval_last_counter = dccp_hdr(skb)->dccph_ccval;
hcrx->ccid3hcrx_bytes_recv = 0;
- /* Elapsed time information [RFC 4340, 13.2] in units of 10 * usecs */
- delta = timeval_delta(&now, &packet->dccphrx_tstamp);
- DCCP_BUG_ON(delta < 0);
- hcrx->ccid3hcrx_elapsed_time = delta / 10;
-
dp->dccps_hc_rx_insert_options = 1;
dccp_send_ack(sk);
}
@@ -1084,7 +1077,7 @@ static void ccid3_hc_rx_packet_recv(stru
ccid3_pr_debug("%s(%p, state=%s), skb=%p, sending initial "
"feedback\n", dccp_role(sk), sk,
dccp_state_name(sk->sk_state), skb);
- ccid3_hc_rx_send_feedback(sk);
+ ccid3_hc_rx_send_feedback(sk, skb);
ccid3_hc_rx_set_state(sk, TFRC_RSTATE_DATA);
return;
case TFRC_RSTATE_DATA:
@@ -1096,7 +1089,7 @@ static void ccid3_hc_rx_packet_recv(stru
if ((timeval_delta(&now, &hcrx->ccid3hcrx_tstamp_last_ack) -
(suseconds_t)hcrx->ccid3hcrx_rtt) >= 0) {
hcrx->ccid3hcrx_tstamp_last_ack = now;
- ccid3_hc_rx_send_feedback(sk);
+ ccid3_hc_rx_send_feedback(sk, skb);
}
return;
case TFRC_RSTATE_TERM:
@@ -1109,7 +1102,7 @@ static void ccid3_hc_rx_packet_recv(stru
dccp_role(sk), sk, dccp_state_name(sk->sk_state));
if (ccid3_hc_rx_update_p(hcrx))
- ccid3_hc_rx_send_feedback(sk);
+ ccid3_hc_rx_send_feedback(sk, skb);
}
static int ccid3_hc_rx_init(struct ccid *ccid, struct sock *sk)
-
To unsubscribe from this list: send the line "unsubscribe dccp" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
