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dccp ccid-3: Fix a loss detection bug 

This fixes a bug in the logic of the TFRC loss detection:
 * new_loss_indicated() should not be called while a loss is pending;
 * but the code allows this;
 * thus, for two subsequent gaps in the sequence space, when loss_count
   has not yet reached NDUPACK=3, the loss_count is falsely reduced to 1.

To avoid further and similar problems, all loss handling and loss detection is
now done inside tfrc_rx_hist_handle_loss(), using an appropriate routine to
track new losses.

Further changes:
----------------
 * added a reminder that no RX history operations should be performed when
   rx_handle_loss() has identified a (new) loss, since the function takes
   care of packet reordering during loss detection;
 * made tfrc_rx_hist_loss_pending() bool (thanks to an earlier suggestion
   by Arnaldo);		 
 * removed unused functions.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This commit is contained in:
Gerrit Renker 2008-07-13 11:51:40 +01:00
parent 5b5d0e7048
commit b552c6231f
3 changed files with 27 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
net/dccp/ccids/ccid3.c
View File

@ -825,18 +825,16 @@ static void ccid3_hc_rx_packet_recv(struct sock *sk, struct sk_buff *skb)
}
/*
* Handle pending losses and otherwise check for new loss
* Perform loss detection and handle pending losses
*/
if (tfrc_rx_hist_loss_pending(&hcrx->ccid3hcrx_hist) &&
tfrc_rx_handle_loss(&hcrx->ccid3hcrx_hist,
&hcrx->ccid3hcrx_li_hist,
skb, ndp, ccid3_first_li, sk) ) {
if (tfrc_rx_handle_loss(&hcrx->ccid3hcrx_hist, &hcrx->ccid3hcrx_li_hist,
skb, ndp, ccid3_first_li, sk)) {
do_feedback = CCID3_FBACK_PARAM_CHANGE;
goto done_receiving;
}
if (tfrc_rx_hist_new_loss_indicated(&hcrx->ccid3hcrx_hist, skb, ndp))
goto update_records;
if (tfrc_rx_hist_loss_pending(&hcrx->ccid3hcrx_hist))
return; /* done receiving */
/*
* Handle data packets: RTT sampling and monitoring p

24
net/dccp/ccids/lib/packet_history.c
View File

@ -206,10 +206,21 @@ static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b)
*
* In the descriptions, `Si' refers to the sequence number of entry number i,
* whose NDP count is `Ni' (lower case is used for variables).
* Note: All __after_loss functions expect that a test against duplicates has
* been performed already: the seqno of the skb must not be less than the
* seqno of loss_prev; and it must not equal that of any valid hist_entry.
* Note: All __xxx_loss functions expect that a test against duplicates has been
* performed already: the seqno of the skb must not be less than the seqno
* of loss_prev; and it must not equal that of any valid history entry.
*/
static void __do_track_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u64 n1)
{
u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
s1 = DCCP_SKB_CB(skb)->dccpd_seq;
if (!dccp_loss_free(s0, s1, n1)) { /* gap between S0 and S1 */
h->loss_count = 1;
tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n1);
}
}
static void __one_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n2)
{
u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno,
@ -353,6 +364,9 @@ static void __three_after_loss(struct tfrc_rx_hist *h)
* Chooses action according to pending loss, updates LI database when a new
* loss was detected, and does required post-processing. Returns 1 when caller
* should send feedback, 0 otherwise.
* Since it also takes care of reordering during loss detection and updates the
* records accordingly, the caller should not perform any more RX history
* operations when loss_count is greater than 0 after calling this function.
*/
int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
struct tfrc_loss_hist *lh,
@ -361,7 +375,9 @@ int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
{
int is_new_loss = 0;
if (h->loss_count == 1) {
if (h->loss_count == 0) {
__do_track_loss(h, skb, ndp);
} else if (h->loss_count == 1) {
__one_after_loss(h, skb, ndp);
} else if (h->loss_count != 2) {
DCCP_BUG("invalid loss_count %d", h->loss_count);

24
net/dccp/ccids/lib/packet_history.h
View File

@ -118,30 +118,10 @@ static inline struct tfrc_rx_hist_entry *
return h->ring[h->loss_start];
}
/* initialise loss detection and disable RTT sampling */
static inline void tfrc_rx_hist_loss_indicated(struct tfrc_rx_hist *h)
{
h->loss_count = 1;
}
/* indicate whether previously a packet was detected missing */
static inline int tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
{
return h->loss_count;
}
/* any data packets missing between last reception and skb ? */
static inline int tfrc_rx_hist_new_loss_indicated(struct tfrc_rx_hist *h,
const struct sk_buff *skb,
u32 ndp)
{
int delta = dccp_delta_seqno(tfrc_rx_hist_last_rcv(h)->tfrchrx_seqno,
DCCP_SKB_CB(skb)->dccpd_seq);
if (delta > 1 && ndp < delta)
tfrc_rx_hist_loss_indicated(h);
return tfrc_rx_hist_loss_pending(h);
return h->loss_count > 0;
}
extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,