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dccp ccid-3: Remove ugly RTT-sampling history lookup
This removes the RTT-sampling function tfrc_tx_hist_rtt(), since 1. it suffered from complex passing of return values (the return value both indicated successful lookup while the value doubled as RTT sample); 2. when for some odd reason the sample value equalled 0, this triggered a bug warning about "bogus Ack", due to the ambiguity of the return value; 3. on a passive host which has not sent anything the TX history is empty and thus will lead to unwanted "bogus Ack" warnings such as ccid3_hc_tx_packet_recv: server(e7b7d518): DATAACK with bogus ACK-28197148 ccid3_hc_tx_packet_recv: server(e7b7d518): DATAACK with bogus ACK-26641606. The fix is to replace the implicit encoding by performing the steps manually. Furthermore, the "bogus Ack" warning has been removed, since it can actually be triggered due to several reasons (network reordering, old packet, (3) above), hence it is not very useful. Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This commit is contained in:
parent
de6f2b59e5
commit
63b3a73bb8
3 changed files with 38 additions and 58 deletions
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@ -371,6 +371,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
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{
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struct ccid3_hc_tx_sock *hctx = ccid3_hc_tx_sk(sk);
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struct ccid3_options_received *opt_recv = &hctx->options_received;
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struct tfrc_tx_hist_entry *acked;
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ktime_t now;
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unsigned long t_nfb;
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u32 pinv, r_sample;
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@ -384,17 +385,24 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
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hctx->state != TFRC_SSTATE_NO_FBACK)
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return;
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now = ktime_get_real();
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/* Estimate RTT from history if ACK number is valid */
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r_sample = tfrc_tx_hist_rtt(hctx->hist,
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DCCP_SKB_CB(skb)->dccpd_ack_seq, now);
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if (r_sample == 0) {
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DCCP_WARN("%s(%p): %s with bogus ACK-%llu\n", dccp_role(sk), sk,
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dccp_packet_name(DCCP_SKB_CB(skb)->dccpd_type),
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(unsigned long long)DCCP_SKB_CB(skb)->dccpd_ack_seq);
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/*
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* Locate the acknowledged packet in the TX history.
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*
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* Returning "entry not found" here can for instance happen when
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* - the host has not sent out anything (e.g. a passive server),
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* - the Ack is outdated (packet with higher Ack number was received),
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* - it is a bogus Ack (for a packet not sent on this connection).
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*/
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acked = tfrc_tx_hist_find_entry(hctx->hist, dccp_hdr_ack_seq(skb));
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if (acked == NULL)
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return;
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}
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/* For the sake of RTT sampling, ignore/remove all older entries */
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tfrc_tx_hist_purge(&acked->next);
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/* Update the moving average for the RTT estimate (RFC 3448, 4.3) */
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now = ktime_get_real();
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r_sample = dccp_sample_rtt(sk, ktime_us_delta(now, acked->stamp));
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hctx->rtt = tfrc_ewma(hctx->rtt, r_sample, 9);
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/* Update receive rate in units of 64 * bytes/second */
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hctx->x_recv = opt_recv->ccid3or_receive_rate;
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@ -406,11 +414,7 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
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hctx->p = 0;
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else /* can not exceed 100% */
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hctx->p = scaled_div(1, pinv);
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/*
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* Validate new RTT sample and update moving average
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*/
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r_sample = dccp_sample_rtt(sk, r_sample);
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hctx->rtt = tfrc_ewma(hctx->rtt, r_sample, 9);
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/*
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* Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3
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*/
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@ -40,18 +40,6 @@
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#include "packet_history.h"
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#include "../../dccp.h"
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/**
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* tfrc_tx_hist_entry - Simple singly-linked TX history list
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* @next: next oldest entry (LIFO order)
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* @seqno: sequence number of this entry
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* @stamp: send time of packet with sequence number @seqno
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*/
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struct tfrc_tx_hist_entry {
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struct tfrc_tx_hist_entry *next;
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u64 seqno;
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ktime_t stamp;
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};
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/*
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* Transmitter History Routines
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*/
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@ -73,15 +61,6 @@ void tfrc_tx_packet_history_exit(void)
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}
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}
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static struct tfrc_tx_hist_entry *
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tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
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{
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while (head != NULL && head->seqno != seqno)
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head = head->next;
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return head;
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}
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int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno)
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{
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struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any());
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@ -111,25 +90,6 @@ void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp)
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}
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EXPORT_SYMBOL_GPL(tfrc_tx_hist_purge);
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u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno,
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const ktime_t now)
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{
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u32 rtt = 0;
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struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno);
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if (packet != NULL) {
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rtt = ktime_us_delta(now, packet->stamp);
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/*
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* Garbage-collect older (irrelevant) entries:
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*/
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tfrc_tx_hist_purge(&packet->next);
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}
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return rtt;
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}
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EXPORT_SYMBOL_GPL(tfrc_tx_hist_rtt);
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/*
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* Receiver History Routines
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*/
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@ -40,12 +40,28 @@
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#include <linux/slab.h>
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#include "tfrc.h"
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struct tfrc_tx_hist_entry;
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/**
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* tfrc_tx_hist_entry - Simple singly-linked TX history list
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* @next: next oldest entry (LIFO order)
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* @seqno: sequence number of this entry
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* @stamp: send time of packet with sequence number @seqno
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*/
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struct tfrc_tx_hist_entry {
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struct tfrc_tx_hist_entry *next;
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u64 seqno;
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ktime_t stamp;
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};
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static inline struct tfrc_tx_hist_entry *
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tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
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{
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while (head != NULL && head->seqno != seqno)
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head = head->next;
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return head;
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}
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extern int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
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extern void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
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extern u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head,
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const u64 seqno, const ktime_t now);
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/* Subtraction a-b modulo-16, respects circular wrap-around */
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#define SUB16(a, b) (((a) + 16 - (b)) & 0xF)
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