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Date: Thu, 28 Oct 2010 07:16:26 +0200
From: Gerrit Renker <gerrit@....abdn.ac.uk>
To: davem@...emloft.net
Cc: dccp@...r.kernel.org, netdev@...r.kernel.org,
Gerrit Renker <gerrit@....abdn.ac.uk>
Subject: [PATCH 2/4] dccp: Extend CCID packet dequeueing interface
This extends the packet dequeuing interface of dccp_write_xmit() to allow
1. CCIDs to take care of timing when the next packet may be sent;
2. delayed sending (as before, with an inter-packet gap up to 65.535 seconds).
The main purpose is to take CCID-2 out of its polling mode (when it is network-
limited, it tries every millisecond to send, without interruption).
The mode of operation for (2) is as follows:
* new packet is enqueued via dccp_sendmsg() => dccp_write_xmit(),
* ccid_hc_tx_send_packet() detects that it may not send (e.g. window full),
* it signals this condition via `CCID_PACKET_WILL_DEQUEUE_LATER',
* dccp_write_xmit() returns without further action;
* after some time the wait-condition for CCID becomes true,
* that CCID schedules the tasklet,
* tasklet function calls ccid_hc_tx_send_packet() via dccp_write_xmit(),
* since the wait-condition is now true, ccid_hc_tx_packet() returns "send now",
* packet is sent, and possibly more (since dccp_write_xmit() loops).
Code reuse: the taskled function calls dccp_write_xmit(), the timer function
reduces to a wrapper around the same code.
Signed-off-by: Gerrit Renker <gerrit@....abdn.ac.uk>
---
include/linux/dccp.h | 4 +-
net/dccp/output.c | 118 ++++++++++++++++++++++++++++++-------------------
net/dccp/timer.c | 25 ++++++-----
3 files changed, 89 insertions(+), 58 deletions(-)
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -462,7 +462,8 @@ struct dccp_ackvec;
* @dccps_hc_rx_insert_options - receiver wants to add options when acking
* @dccps_hc_tx_insert_options - sender wants to add options when sending
* @dccps_server_timewait - server holds timewait state on close (RFC 4340, 8.3)
- * @dccps_xmit_timer - timer for when CCID is not ready to send
+ * @dccps_xmitlet - tasklet scheduled by the TX CCID to dequeue data packets
+ * @dccps_xmit_timer - used by the TX CCID to delay sending (rate-based pacing)
* @dccps_syn_rtt - RTT sample from Request/Response exchange (in usecs)
*/
struct dccp_sock {
@@ -502,6 +503,7 @@ struct dccp_sock {
__u8 dccps_hc_rx_insert_options:1;
__u8 dccps_hc_tx_insert_options:1;
__u8 dccps_server_timewait:1;
+ struct tasklet_struct dccps_xmitlet;
struct timer_list dccps_xmit_timer;
};
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -254,63 +254,89 @@ do_interrupted:
goto out;
}
+/**
+ * dccp_xmit_packet - Send data packet under control of CCID
+ * Transmits next-queued payload and informs CCID to account for the packet.
+ */
+static void dccp_xmit_packet(struct sock *sk)
+{
+ int err, len;
+ struct dccp_sock *dp = dccp_sk(sk);
+ struct sk_buff *skb = skb_dequeue(&sk->sk_write_queue);
+
+ if (unlikely(skb == NULL))
+ return;
+ len = skb->len;
+
+ if (sk->sk_state == DCCP_PARTOPEN) {
+ const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
+ /*
+ * See 8.1.5 - Handshake Completion.
+ *
+ * For robustness we resend Confirm options until the client has
+ * entered OPEN. During the initial feature negotiation, the MPS
+ * is smaller than usual, reduced by the Change/Confirm options.
+ */
+ if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
+ DCCP_WARN("Payload too large (%d) for featneg.\n", len);
+ dccp_send_ack(sk);
+ dccp_feat_list_purge(&dp->dccps_featneg);
+ }
+
+ inet_csk_schedule_ack(sk);
+ inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
+ inet_csk(sk)->icsk_rto,
+ DCCP_RTO_MAX);
+ DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
+ } else if (dccp_ack_pending(sk)) {
+ DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
+ } else {
+ DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;
+ }
+
+ err = dccp_transmit_skb(sk, skb);
+ if (err)
+ dccp_pr_debug("transmit_skb() returned err=%d\n", err);
+ /*
+ * Register this one as sent even if an error occurred. To the remote
+ * end a local packet drop is indistinguishable from network loss, i.e.
+ * any local drop will eventually be reported via receiver feedback.
+ */
+ ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
+}
+
void dccp_write_xmit(struct sock *sk, int block)
{
struct dccp_sock *dp = dccp_sk(sk);
struct sk_buff *skb;
while ((skb = skb_peek(&sk->sk_write_queue))) {
- int err = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
+ int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
- if (err > 0) {
+ switch (ccid_packet_dequeue_eval(rc)) {
+ case CCID_PACKET_WILL_DEQUEUE_LATER:
+ return;
+ case CCID_PACKET_DELAY:
if (!block) {
sk_reset_timer(sk, &dp->dccps_xmit_timer,
- msecs_to_jiffies(err)+jiffies);
+ msecs_to_jiffies(rc)+jiffies);
+ return;
+ }
+ rc = dccp_wait_for_ccid(sk, skb, rc);
+ if (rc && rc != -EINTR) {
+ DCCP_BUG("err=%d after dccp_wait_for_ccid", rc);
+ skb_dequeue(&sk->sk_write_queue);
+ kfree_skb(skb);
break;
- } else
- err = dccp_wait_for_ccid(sk, skb, err);
- if (err && err != -EINTR)
- DCCP_BUG("err=%d after dccp_wait_for_ccid", err);
- }
-
- skb_dequeue(&sk->sk_write_queue);
- if (err == 0) {
- struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
- const int len = skb->len;
-
- if (sk->sk_state == DCCP_PARTOPEN) {
- const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
- /*
- * See 8.1.5 - Handshake Completion.
- *
- * For robustness we resend Confirm options until the client has
- * entered OPEN. During the initial feature negotiation, the MPS
- * is smaller than usual, reduced by the Change/Confirm options.
- */
- if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
- DCCP_WARN("Payload too large (%d) for featneg.\n", len);
- dccp_send_ack(sk);
- dccp_feat_list_purge(&dp->dccps_featneg);
- }
-
- inet_csk_schedule_ack(sk);
- inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
- inet_csk(sk)->icsk_rto,
- DCCP_RTO_MAX);
- dcb->dccpd_type = DCCP_PKT_DATAACK;
- } else if (dccp_ack_pending(sk))
- dcb->dccpd_type = DCCP_PKT_DATAACK;
- else
- dcb->dccpd_type = DCCP_PKT_DATA;
-
- err = dccp_transmit_skb(sk, skb);
- ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
- if (err)
- DCCP_BUG("err=%d after ccid_hc_tx_packet_sent",
- err);
- } else {
- dccp_pr_debug("packet discarded due to err=%d\n", err);
+ }
+ /* fall through */
+ case CCID_PACKET_SEND_AT_ONCE:
+ dccp_xmit_packet(sk);
+ break;
+ case CCID_PACKET_ERR:
+ skb_dequeue(&sk->sk_write_queue);
kfree_skb(skb);
+ dccp_pr_debug("packet discarded due to err=%d\n", rc);
}
}
}
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -237,32 +237,35 @@ out:
sock_put(sk);
}
-/* Transmit-delay timer: used by the CCIDs to delay actual send time */
-static void dccp_write_xmit_timer(unsigned long data)
+/**
+ * dccp_write_xmitlet - Workhorse for CCID packet dequeueing interface
+ * See the comments above %ccid_dequeueing_decision for supported modes.
+ */
+static void dccp_write_xmitlet(unsigned long data)
{
struct sock *sk = (struct sock *)data;
- struct dccp_sock *dp = dccp_sk(sk);
bh_lock_sock(sk);
if (sock_owned_by_user(sk))
- sk_reset_timer(sk, &dp->dccps_xmit_timer, jiffies+1);
+ sk_reset_timer(sk, &dccp_sk(sk)->dccps_xmit_timer, jiffies + 1);
else
dccp_write_xmit(sk, 0);
bh_unlock_sock(sk);
- sock_put(sk);
}
-static void dccp_init_write_xmit_timer(struct sock *sk)
+static void dccp_write_xmit_timer(unsigned long data)
{
- struct dccp_sock *dp = dccp_sk(sk);
-
- setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer,
- (unsigned long)sk);
+ dccp_write_xmitlet(data);
+ sock_put((struct sock *)data);
}
void dccp_init_xmit_timers(struct sock *sk)
{
- dccp_init_write_xmit_timer(sk);
+ struct dccp_sock *dp = dccp_sk(sk);
+
+ tasklet_init(&dp->dccps_xmitlet, dccp_write_xmitlet, (unsigned long)sk);
+ setup_timer(&dp->dccps_xmit_timer, dccp_write_xmit_timer,
+ (unsigned long)sk);
inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
&dccp_keepalive_timer);
}
--
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