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dccp: Extend CCID packet dequeueing interface

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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 CCID2 out of its polling mode (when it is network-
limited, it tries every millisecond to send, without interruption).
The interface can also be used to support other CCIDs.

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.

If the tasklet finds that the socket is locked, it re-schedules the tasklet
function (not the tasklet) after one jiffy.

Changed DCCP_BUG to dccp_pr_debug when transmit_skb returns an error (e.g. when a
local qdisc is used, NET_XMIT_DROP=1 can be returned for many packets).

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 f4a66ca4d2
commit e7937772d7
3 changed files with 98 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/dccp.h
View File

@ -463,7 +463,8 @@ struct dccp_ackvec;
* @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_sync_scheduled - flag which signals "send out-of-band message soon"
* @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 {
@ -504,6 +505,7 @@ struct dccp_sock {
__u8 dccps_hc_tx_insert_options:1;
__u8 dccps_server_timewait:1;
__u8 dccps_sync_scheduled:1;
struct tasklet_struct dccps_xmitlet;
struct timer_list dccps_xmit_timer;
};

129
net/dccp/output.c
View File

@ -251,65 +251,98 @@ 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);
/*
* If the CCID needs to transfer additional header options out-of-band
* (e.g. Ack Vectors or feature-negotiation options), it activates this
* flag to schedule a Sync. The Sync will automatically incorporate all
* currently pending header options, thus clearing the backlog.
*/
if (dp->dccps_sync_scheduled)
dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
}
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);
if (dp->dccps_sync_scheduled)
dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
} 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);
}
}
}

25
net/dccp/timer.c
View File

@ -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);
}