1 files changed, 108 insertions, 181 deletions

diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 9b3ae9922be1..d850e291f87c 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -25,59 +25,14 @@
  */
 #include <linux/slab.h>
 #include "../feat.h"
-#include "../ccid.h"
-#include "../dccp.h"
 #include "ccid2.h"
 
 
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
 static int ccid2_debug;
 #define ccid2_pr_debug(format, a...)    DCCP_PR_DEBUG(ccid2_debug, format, ##a)
-
-static void ccid2_hc_tx_check_sanity(const struct ccid2_hc_tx_sock *hc)
-{
-        int len = 0;
-        int pipe = 0;
-        struct ccid2_seq *seqp = hc->tx_seqh;
-
-        /* there is data in the chain */
-        if (seqp != hc->tx_seqt) {
-                seqp = seqp->ccid2s_prev;
-                len++;
-                if (!seqp->ccid2s_acked)
-                        pipe++;
-
-                while (seqp != hc->tx_seqt) {
-                        struct ccid2_seq *prev = seqp->ccid2s_prev;
-
-                        len++;
-                        if (!prev->ccid2s_acked)
-                                pipe++;
-
-                        /* packets are sent sequentially */
-                        BUG_ON(dccp_delta_seqno(seqp->ccid2s_seq,
-                                                prev->ccid2s_seq ) >= 0);
-                        BUG_ON(time_before(seqp->ccid2s_sent,
-                                           prev->ccid2s_sent));
-
-                        seqp = prev;
-                }
-        }
-
-        BUG_ON(pipe != hc->tx_pipe);
-        ccid2_pr_debug("len of chain=%d\n", len);
-
-        do {
-                seqp = seqp->ccid2s_prev;
-                len++;
-        } while (seqp != hc->tx_seqh);
-
-        ccid2_pr_debug("total len=%d\n", len);
-        BUG_ON(len != hc->tx_seqbufc * CCID2_SEQBUF_LEN);
-}
 #else
 #define ccid2_pr_debug(format, a...)
-#define ccid2_hc_tx_check_sanity(hc)
 #endif
 
 static int ccid2_hc_tx_alloc_seq(struct ccid2_hc_tx_sock *hc)
@@ -156,19 +111,10 @@ static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
         dp->dccps_l_ack_ratio = val;
 }
 
-static void ccid2_change_srtt(struct ccid2_hc_tx_sock *hc, long val)
-{
-        ccid2_pr_debug("change SRTT to %ld\n", val);
-        hc->tx_srtt = val;
-}
-
-static void ccid2_start_rto_timer(struct sock *sk);
-
 static void ccid2_hc_tx_rto_expire(unsigned long data)
 {
         struct sock *sk = (struct sock *)data;
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
-        long s;
 
         bh_lock_sock(sk);
         if (sock_owned_by_user(sk)) {
@@ -178,23 +124,19 @@ static void ccid2_hc_tx_rto_expire(unsigned long data)
 
         ccid2_pr_debug("RTO_EXPIRE\n");
 
-        ccid2_hc_tx_check_sanity(hc);
-
         /* back-off timer */
         hc->tx_rto <<= 1;
+        if (hc->tx_rto > DCCP_RTO_MAX)
+                hc->tx_rto = DCCP_RTO_MAX;
 
-        s = hc->tx_rto / HZ;
-        if (s > 60)
-                hc->tx_rto = 60 * HZ;
-
-        ccid2_start_rto_timer(sk);
+        sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
 
         /* adjust pipe, cwnd etc */
         hc->tx_ssthresh = hc->tx_cwnd / 2;
         if (hc->tx_ssthresh < 2)
                 hc->tx_ssthresh = 2;
-        hc->tx_cwnd      = 1;
-        hc->tx_pipe      = 0;
+        hc->tx_cwnd     = 1;
+        hc->tx_pipe     = 0;
 
         /* clear state about stuff we sent */
         hc->tx_seqt = hc->tx_seqh;
@@ -204,23 +146,12 @@ static void ccid2_hc_tx_rto_expire(unsigned long data)
         hc->tx_rpseq    = 0;
         hc->tx_rpdupack = -1;
         ccid2_change_l_ack_ratio(sk, 1);
-        ccid2_hc_tx_check_sanity(hc);
 out:
         bh_unlock_sock(sk);
         sock_put(sk);
 }
 
-static void ccid2_start_rto_timer(struct sock *sk)
-{
-        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
-
-        ccid2_pr_debug("setting RTO timeout=%ld\n", hc->tx_rto);
-
-        BUG_ON(timer_pending(&hc->tx_rtotimer));
-        sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
-}
-
-static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
+static void ccid2_hc_tx_packet_sent(struct sock *sk, unsigned int len)
 {
         struct dccp_sock *dp = dccp_sk(sk);
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
@@ -230,7 +161,7 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
 
         hc->tx_seqh->ccid2s_seq   = dp->dccps_gss;
         hc->tx_seqh->ccid2s_acked = 0;
-        hc->tx_seqh->ccid2s_sent  = jiffies;
+        hc->tx_seqh->ccid2s_sent  = ccid2_time_stamp;
 
         next = hc->tx_seqh->ccid2s_next;
         /* check if we need to alloc more space */
@@ -296,23 +227,20 @@ static void ccid2_hc_tx_packet_sent(struct sock *sk, int more, unsigned int len)
         }
 #endif
 
-        /* setup RTO timer */
-        if (!timer_pending(&hc->tx_rtotimer))
-                ccid2_start_rto_timer(sk);
+        sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
 
 #ifdef CONFIG_IP_DCCP_CCID2_DEBUG
         do {
                 struct ccid2_seq *seqp = hc->tx_seqt;
 
                 while (seqp != hc->tx_seqh) {
-                        ccid2_pr_debug("out seq=%llu acked=%d time=%lu\n",
+                        ccid2_pr_debug("out seq=%llu acked=%d time=%u\n",
                                        (unsigned long long)seqp->ccid2s_seq,
                                        seqp->ccid2s_acked, seqp->ccid2s_sent);
                         seqp = seqp->ccid2s_next;
                 }
         } while (0);
         ccid2_pr_debug("=========\n");
-        ccid2_hc_tx_check_sanity(hc);
 #endif
 }
 
@@ -378,17 +306,87 @@ out_invalid_option:
         return -1;
 }
 
-static void ccid2_hc_tx_kill_rto_timer(struct sock *sk)
+/**
+ * ccid2_rtt_estimator - Sample RTT and compute RTO using RFC2988 algorithm
+ * This code is almost identical with TCP's tcp_rtt_estimator(), since
+ * - it has a higher sampling frequency (recommended by RFC 1323),
+ * - the RTO does not collapse into RTT due to RTTVAR going towards zero,
+ * - it is simple (cf. more complex proposals such as Eifel timer or research
+ *   which suggests that the gain should be set according to window size),
+ * - in tests it was found to work well with CCID2 [gerrit].
+ */
+static void ccid2_rtt_estimator(struct sock *sk, const long mrtt)
 {
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
+        long m = mrtt ? : 1;
 
-        sk_stop_timer(sk, &hc->tx_rtotimer);
-        ccid2_pr_debug("deleted RTO timer\n");
+        if (hc->tx_srtt == 0) {
+                /* First measurement m */
+                hc->tx_srtt = m << 3;
+                hc->tx_mdev = m << 1;
+
+                hc->tx_mdev_max = max(hc->tx_mdev, tcp_rto_min(sk));
+                hc->tx_rttvar   = hc->tx_mdev_max;
+
+                hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
+        } else {
+                /* Update scaled SRTT as SRTT += 1/8 * (m - SRTT) */
+                m -= (hc->tx_srtt >> 3);
+                hc->tx_srtt += m;
+
+                /* Similarly, update scaled mdev with regard to |m| */
+                if (m < 0) {
+                        m = -m;
+                        m -= (hc->tx_mdev >> 2);
+                        /*
+                         * This neutralises RTO increase when RTT < SRTT - mdev
+                         * (see P. Sarolahti, A. Kuznetsov,"Congestion Control
+                         * in Linux TCP", USENIX 2002, pp. 49-62).
+                         */
+                        if (m > 0)
+                                m >>= 3;
+                } else {
+                        m -= (hc->tx_mdev >> 2);
+                }
+                hc->tx_mdev += m;
+
+                if (hc->tx_mdev > hc->tx_mdev_max) {
+                        hc->tx_mdev_max = hc->tx_mdev;
+                        if (hc->tx_mdev_max > hc->tx_rttvar)
+                                hc->tx_rttvar = hc->tx_mdev_max;
+                }
+
+                /*
+                 * Decay RTTVAR at most once per flight, exploiting that
+                 *  1) pipe <= cwnd <= Sequence_Window = W  (RFC 4340, 7.5.2)
+                 *  2) AWL = GSS-W+1 <= GAR <= GSS          (RFC 4340, 7.5.1)
+                 * GAR is a useful bound for FlightSize = pipe.
+                 * AWL is probably too low here, as it over-estimates pipe.
+                 */
+                if (after48(dccp_sk(sk)->dccps_gar, hc->tx_rtt_seq)) {
+                        if (hc->tx_mdev_max < hc->tx_rttvar)
+                                hc->tx_rttvar -= (hc->tx_rttvar -
+                                                  hc->tx_mdev_max) >> 2;
+                        hc->tx_rtt_seq  = dccp_sk(sk)->dccps_gss;
+                        hc->tx_mdev_max = tcp_rto_min(sk);
+                }
+        }
+
+        /*
+         * Set RTO from SRTT and RTTVAR
+         * As in TCP, 4 * RTTVAR >= TCP_RTO_MIN, giving a minimum RTO of 200 ms.
+         * This agrees with RFC 4341, 5:
+         *      "Because DCCP does not retransmit data, DCCP does not require
+         *       TCP's recommended minimum timeout of one second".
+         */
+        hc->tx_rto = (hc->tx_srtt >> 3) + hc->tx_rttvar;
+
+        if (hc->tx_rto > DCCP_RTO_MAX)
+                hc->tx_rto = DCCP_RTO_MAX;
 }
 
-static inline void ccid2_new_ack(struct sock *sk,
-                                 struct ccid2_seq *seqp,
-                                 unsigned int *maxincr)
+static void ccid2_new_ack(struct sock *sk, struct ccid2_seq *seqp,
+                          unsigned int *maxincr)
 {
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
 
@@ -402,93 +400,27 @@ static inline void ccid2_new_ack(struct sock *sk,
                         hc->tx_cwnd += 1;
                         hc->tx_packets_acked = 0;
         }
-
-        /* update RTO */
-        if (hc->tx_srtt == -1 ||
-            time_after(jiffies, hc->tx_lastrtt + hc->tx_srtt)) {
-                unsigned long r = (long)jiffies - (long)seqp->ccid2s_sent;
-                int s;
-
-                /* first measurement */
-                if (hc->tx_srtt == -1) {
-                        ccid2_pr_debug("R: %lu Time=%lu seq=%llu\n",
-                                       r, jiffies,
-                                       (unsigned long long)seqp->ccid2s_seq);
-                        ccid2_change_srtt(hc, r);
-                        hc->tx_rttvar = r >> 1;
-                } else {
-                        /* RTTVAR */
-                        long tmp = hc->tx_srtt - r;
-                        long srtt;
-
-                        if (tmp < 0)
-                                tmp *= -1;
-
-                        tmp >>= 2;
-                        hc->tx_rttvar *= 3;
-                        hc->tx_rttvar >>= 2;
-                        hc->tx_rttvar += tmp;
-
-                        /* SRTT */
-                        srtt = hc->tx_srtt;
-                        srtt *= 7;
-                        srtt >>= 3;
-                        tmp = r >> 3;
-                        srtt += tmp;
-                        ccid2_change_srtt(hc, srtt);
-                }
-                s = hc->tx_rttvar << 2;
-                /* clock granularity is 1 when based on jiffies */
-                if (!s)
-                        s = 1;
-                hc->tx_rto = hc->tx_srtt + s;
-
-                /* must be at least a second */
-                s = hc->tx_rto / HZ;
-                /* DCCP doesn't require this [but I like it cuz my code sux] */
-#if 1
-                if (s < 1)
-                        hc->tx_rto = HZ;
-#endif
-                /* max 60 seconds */
-                if (s > 60)
-                        hc->tx_rto = HZ * 60;
-
-                hc->tx_lastrtt = jiffies;
-
-                ccid2_pr_debug("srtt: %ld rttvar: %ld rto: %ld (HZ=%d) R=%lu\n",
-                               hc->tx_srtt, hc->tx_rttvar,
-                               hc->tx_rto, HZ, r);
-        }
-
-        /* we got a new ack, so re-start RTO timer */
-        ccid2_hc_tx_kill_rto_timer(sk);
-        ccid2_start_rto_timer(sk);
-}
-
-static void ccid2_hc_tx_dec_pipe(struct sock *sk)
-{
-        struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
-
-        if (hc->tx_pipe == 0)
-                DCCP_BUG("pipe == 0");
-        else
-                hc->tx_pipe--;
-
-        if (hc->tx_pipe == 0)
-                ccid2_hc_tx_kill_rto_timer(sk);
+        /*
+         * FIXME: RTT is sampled several times per acknowledgment (for each
+         * entry in the Ack Vector), instead of once per Ack (as in TCP SACK).
+         * This causes the RTT to be over-estimated, since the older entries
+         * in the Ack Vector have earlier sending times.
+         * The cleanest solution is to not use the ccid2s_sent field at all
+         * and instead use DCCP timestamps: requires changes in other places.
+         */
+        ccid2_rtt_estimator(sk, ccid2_time_stamp - seqp->ccid2s_sent);
 }
 
 static void ccid2_congestion_event(struct sock *sk, struct ccid2_seq *seqp)
 {
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
 
-        if (time_before(seqp->ccid2s_sent, hc->tx_last_cong)) {
+        if ((s32)(seqp->ccid2s_sent - hc->tx_last_cong) < 0) {
                 ccid2_pr_debug("Multiple losses in an RTT---treating as one\n");
                 return;
         }
 
-        hc->tx_last_cong = jiffies;
+        hc->tx_last_cong = ccid2_time_stamp;
 
         hc->tx_cwnd      = hc->tx_cwnd / 2 ? : 1U;
         hc->tx_ssthresh  = max(hc->tx_cwnd, 2U);
@@ -510,7 +442,6 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
         int done = 0;
         unsigned int maxincr = 0;
 
-        ccid2_hc_tx_check_sanity(hc);
         /* check reverse path congestion */
         seqno = DCCP_SKB_CB(skb)->dccpd_seq;
 
@@ -620,7 +551,7 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                                         seqp->ccid2s_acked = 1;
                                         ccid2_pr_debug("Got ack for %llu\n",
                                                        (unsigned long long)seqp->ccid2s_seq);
-                                        ccid2_hc_tx_dec_pipe(sk);
+                                        hc->tx_pipe--;
                                 }
                                 if (seqp == hc->tx_seqt) {
                                         done = 1;
@@ -677,7 +608,7 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                                  * one ack vector.
                                  */
                                 ccid2_congestion_event(sk, seqp);
-                                ccid2_hc_tx_dec_pipe(sk);
+                                hc->tx_pipe--;
                         }
                         if (seqp == hc->tx_seqt)
                                 break;
@@ -695,7 +626,11 @@ static void ccid2_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb)
                 hc->tx_seqt = hc->tx_seqt->ccid2s_next;
         }
 
-        ccid2_hc_tx_check_sanity(hc);
+        /* restart RTO timer if not all outstanding data has been acked */
+        if (hc->tx_pipe == 0)
+                sk_stop_timer(sk, &hc->tx_rtotimer);
+        else
+                sk_reset_timer(sk, &hc->tx_rtotimer, jiffies + hc->tx_rto);
 }
 
 static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
@@ -707,12 +642,8 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
         /* RFC 4341, 5: initialise ssthresh to arbitrarily high (max) value */
         hc->tx_ssthresh = ~0U;
 
-        /*
-         * RFC 4341, 5: "The cwnd parameter is initialized to at most four
-         * packets for new connections, following the rules from [RFC3390]".
-         * We need to convert the bytes of RFC3390 into the packets of RFC 4341.
-         */
-        hc->tx_cwnd = clamp(4380U / dp->dccps_mss_cache, 2U, 4U);
+        /* Use larger initial windows (RFC 4341, section 5). */
+        hc->tx_cwnd = rfc3390_bytes_to_packets(dp->dccps_mss_cache);
 
         /* Make sure that Ack Ratio is enabled and within bounds. */
         max_ratio = DIV_ROUND_UP(hc->tx_cwnd, 2);
@@ -723,15 +654,11 @@ static int ccid2_hc_tx_init(struct ccid *ccid, struct sock *sk)
         if (ccid2_hc_tx_alloc_seq(hc))
                 return -ENOMEM;
 
-        hc->tx_rto       = 3 * HZ;
-        ccid2_change_srtt(hc, -1);
-        hc->tx_rttvar    = -1;
+        hc->tx_rto       = DCCP_TIMEOUT_INIT;
         hc->tx_rpdupack  = -1;
-        hc->tx_last_cong = jiffies;
+        hc->tx_last_cong = ccid2_time_stamp;
         setup_timer(&hc->tx_rtotimer, ccid2_hc_tx_rto_expire,
                         (unsigned long)sk);
-
-        ccid2_hc_tx_check_sanity(hc);
         return 0;
 }
 
@@ -740,7 +667,7 @@ static void ccid2_hc_tx_exit(struct sock *sk)
         struct ccid2_hc_tx_sock *hc = ccid2_hc_tx_sk(sk);
         int i;
 
-        ccid2_hc_tx_kill_rto_timer(sk);
+        sk_stop_timer(sk, &hc->tx_rtotimer);
 
         for (i = 0; i < hc->tx_seqbufc; i++)
                 kfree(hc->tx_seqbuf[i]);