/* * Copyright (c) 2007 The University of Aberdeen, Scotland, UK * Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand. * * An implementation of the DCCP protocol * * This code has been developed by the University of Waikato WAND * research group. For further information please see http://www.wand.net.nz/ * or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz * * This code also uses code from Lulea University, rereleased as GPL by its * authors: * Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon * * Changes to meet Linux coding standards, to make it meet latest ccid3 draft * and to make it work as a loadable module in the DCCP stack written by * Arnaldo Carvalho de Melo <acme@conectiva.com.br>. * * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #include <linux/string.h> #include <linux/slab.h> #include "packet_history.h" #include "../../dccp.h" /** * tfrc_tx_hist_entry - Simple singly-linked TX history list * @next: next oldest entry (LIFO order) * @seqno: sequence number of this entry * @stamp: send time of packet with sequence number @seqno */ struct tfrc_tx_hist_entry { struct tfrc_tx_hist_entry *next; u64 seqno; ktime_t stamp; }; /* * Transmitter History Routines */ static struct kmem_cache *tfrc_tx_hist_slab; int __init tfrc_tx_packet_history_init(void) { tfrc_tx_hist_slab = kmem_cache_create("tfrc_tx_hist", sizeof(struct tfrc_tx_hist_entry), 0, SLAB_HWCACHE_ALIGN, NULL); return tfrc_tx_hist_slab == NULL ? -ENOBUFS : 0; } void tfrc_tx_packet_history_exit(void) { if (tfrc_tx_hist_slab != NULL) { kmem_cache_destroy(tfrc_tx_hist_slab); tfrc_tx_hist_slab = NULL; } } static struct tfrc_tx_hist_entry * tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno) { while (head != NULL && head->seqno != seqno) head = head->next; return head; } int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno) { struct tfrc_tx_hist_entry *entry = kmem_cache_alloc(tfrc_tx_hist_slab, gfp_any()); if (entry == NULL) return -ENOBUFS; entry->seqno = seqno; entry->stamp = ktime_get_real(); entry->next = *headp; *headp = entry; return 0; } void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp) { struct tfrc_tx_hist_entry *head = *headp; while (head != NULL) { struct tfrc_tx_hist_entry *next = head->next; kmem_cache_free(tfrc_tx_hist_slab, head); head = next; } *headp = NULL; } u32 tfrc_tx_hist_rtt(struct tfrc_tx_hist_entry *head, const u64 seqno, const ktime_t now) { u32 rtt = 0; struct tfrc_tx_hist_entry *packet = tfrc_tx_hist_find_entry(head, seqno); if (packet != NULL) { rtt = ktime_us_delta(now, packet->stamp); /* * Garbage-collect older (irrelevant) entries: */ tfrc_tx_hist_purge(&packet->next); } return rtt; } /* * Receiver History Routines */ static struct kmem_cache *tfrc_rx_hist_slab; int __init tfrc_rx_packet_history_init(void) { tfrc_rx_hist_slab = kmem_cache_create("tfrc_rxh_cache", sizeof(struct tfrc_rx_hist_entry), 0, SLAB_HWCACHE_ALIGN, NULL); return tfrc_rx_hist_slab == NULL ? -ENOBUFS : 0; } void tfrc_rx_packet_history_exit(void) { if (tfrc_rx_hist_slab != NULL) { kmem_cache_destroy(tfrc_rx_hist_slab); tfrc_rx_hist_slab = NULL; } } static inline void tfrc_rx_hist_entry_from_skb(struct tfrc_rx_hist_entry *entry, const struct sk_buff *skb, const u64 ndp) { const struct dccp_hdr *dh = dccp_hdr(skb); entry->tfrchrx_seqno = DCCP_SKB_CB(skb)->dccpd_seq; entry->tfrchrx_ccval = dh->dccph_ccval; entry->tfrchrx_type = dh->dccph_type; entry->tfrchrx_ndp = ndp; entry->tfrchrx_tstamp = ktime_get_real(); } void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h, const struct sk_buff *skb, const u64 ndp) { struct tfrc_rx_hist_entry *entry = tfrc_rx_hist_last_rcv(h); tfrc_rx_hist_entry_from_skb(entry, skb, ndp); } /* has the packet contained in skb been seen before? */ int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb) { const u64 seq = DCCP_SKB_CB(skb)->dccpd_seq; int i; if (dccp_delta_seqno(tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, seq) <= 0) return 1; for (i = 1; i <= h->loss_count; i++) if (tfrc_rx_hist_entry(h, i)->tfrchrx_seqno == seq) return 1; return 0; } static void tfrc_rx_hist_swap(struct tfrc_rx_hist *h, const u8 a, const u8 b) { const u8 idx_a = tfrc_rx_hist_index(h, a), idx_b = tfrc_rx_hist_index(h, b); struct tfrc_rx_hist_entry *tmp = h->ring[idx_a]; h->ring[idx_a] = h->ring[idx_b]; h->ring[idx_b] = tmp; } /* * Private helper functions for loss detection. * * 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 __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, s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno, s2 = DCCP_SKB_CB(skb)->dccpd_seq; if (likely(dccp_delta_seqno(s1, s2) > 0)) { /* S1 < S2 */ h->loss_count = 2; tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n2); return; } /* S0 < S2 < S1 */ if (dccp_loss_free(s0, s2, n2)) { u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp; if (dccp_loss_free(s2, s1, n1)) { /* hole is filled: S0, S2, and S1 are consecutive */ h->loss_count = 0; h->loss_start = tfrc_rx_hist_index(h, 1); } else /* gap between S2 and S1: just update loss_prev */ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n2); } else { /* gap between S0 and S2 */ /* * Reorder history to insert S2 between S0 and S1 */ tfrc_rx_hist_swap(h, 0, 3); h->loss_start = tfrc_rx_hist_index(h, 3); tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n2); h->loss_count = 2; } } /* return 1 if a new loss event has been identified */ static int __two_after_loss(struct tfrc_rx_hist *h, struct sk_buff *skb, u32 n3) { u64 s0 = tfrc_rx_hist_loss_prev(h)->tfrchrx_seqno, s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno, s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno, s3 = DCCP_SKB_CB(skb)->dccpd_seq; if (likely(dccp_delta_seqno(s2, s3) > 0)) { /* S2 < S3 */ h->loss_count = 3; tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 3), skb, n3); return 1; } /* S3 < S2 */ if (dccp_delta_seqno(s1, s3) > 0) { /* S1 < S3 < S2 */ /* * Reorder history to insert S3 between S1 and S2 */ tfrc_rx_hist_swap(h, 2, 3); tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 2), skb, n3); h->loss_count = 3; return 1; } /* S0 < S3 < S1 */ if (dccp_loss_free(s0, s3, n3)) { u64 n1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_ndp; if (dccp_loss_free(s3, s1, n1)) { /* hole between S0 and S1 filled by S3 */ u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp; if (dccp_loss_free(s1, s2, n2)) { /* entire hole filled by S0, S3, S1, S2 */ h->loss_start = tfrc_rx_hist_index(h, 2); h->loss_count = 0; } else { /* gap remains between S1 and S2 */ h->loss_start = tfrc_rx_hist_index(h, 1); h->loss_count = 1; } } else /* gap exists between S3 and S1, loss_count stays at 2 */ tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_loss_prev(h), skb, n3); return 0; } /* * The remaining case: S0 < S3 < S1 < S2; gap between S0 and S3 * Reorder history to insert S3 between S0 and S1. */ tfrc_rx_hist_swap(h, 0, 3); h->loss_start = tfrc_rx_hist_index(h, 3); tfrc_rx_hist_entry_from_skb(tfrc_rx_hist_entry(h, 1), skb, n3); h->loss_count = 3; return 1; } /* recycle RX history records to continue loss detection if necessary */ static void __three_after_loss(struct tfrc_rx_hist *h) { /* * At this stage we know already that there is a gap between S0 and S1 * (since S0 was the highest sequence number received before detecting * the loss). To recycle the loss record, it is thus only necessary to * check for other possible gaps between S1/S2 and between S2/S3. */ u64 s1 = tfrc_rx_hist_entry(h, 1)->tfrchrx_seqno, s2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_seqno, s3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_seqno; u64 n2 = tfrc_rx_hist_entry(h, 2)->tfrchrx_ndp, n3 = tfrc_rx_hist_entry(h, 3)->tfrchrx_ndp; if (dccp_loss_free(s1, s2, n2)) { if (dccp_loss_free(s2, s3, n3)) { /* no gap between S2 and S3: entire hole is filled */ h->loss_start = tfrc_rx_hist_index(h, 3); h->loss_count = 0; } else { /* gap between S2 and S3 */ h->loss_start = tfrc_rx_hist_index(h, 2); h->loss_count = 1; } } else { /* gap between S1 and S2 */ h->loss_start = tfrc_rx_hist_index(h, 1); h->loss_count = 2; } } /** * tfrc_rx_handle_loss - Loss detection and further processing * @h: The non-empty RX history object * @lh: Loss Intervals database to update * @skb: Currently received packet * @ndp: The NDP count belonging to @skb * @calc_first_li: Caller-dependent computation of first loss interval in @lh * @sk: Used by @calc_first_li (see tfrc_lh_interval_add) * 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, struct sk_buff *skb, const u64 ndp, u32 (*calc_first_li)(struct sock *), struct sock *sk) { int is_new_loss = 0; 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); } else if (__two_after_loss(h, skb, ndp)) { /* * Update Loss Interval database and recycle RX records */ is_new_loss = tfrc_lh_interval_add(lh, h, calc_first_li, sk); __three_after_loss(h); } return is_new_loss; } int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h) { int i; for (i = 0; i <= TFRC_NDUPACK; i++) { h->ring[i] = kmem_cache_alloc(tfrc_rx_hist_slab, GFP_ATOMIC); if (h->ring[i] == NULL) goto out_free; } h->loss_count = h->loss_start = 0; return 0; out_free: while (i-- != 0) { kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]); h->ring[i] = NULL; } return -ENOBUFS; } void tfrc_rx_hist_purge(struct tfrc_rx_hist *h) { int i; for (i = 0; i <= TFRC_NDUPACK; ++i) if (h->ring[i] != NULL) { kmem_cache_free(tfrc_rx_hist_slab, h->ring[i]); h->ring[i] = NULL; } } /** * tfrc_rx_hist_rtt_last_s - reference entry to compute RTT samples against */ static inline struct tfrc_rx_hist_entry * tfrc_rx_hist_rtt_last_s(const struct tfrc_rx_hist *h) { return h->ring[0]; } /** * tfrc_rx_hist_rtt_prev_s: previously suitable (wrt rtt_last_s) RTT-sampling entry */ static inline struct tfrc_rx_hist_entry * tfrc_rx_hist_rtt_prev_s(const struct tfrc_rx_hist *h) { return h->ring[h->rtt_sample_prev]; } /** * tfrc_rx_hist_sample_rtt - Sample RTT from timestamp / CCVal * Based on ideas presented in RFC 4342, 8.1. Returns 0 if it was not able * to compute a sample with given data - calling function should check this. */ u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h, const struct sk_buff *skb) { u32 sample = 0, delta_v = SUB16(dccp_hdr(skb)->dccph_ccval, tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); if (delta_v < 1 || delta_v > 4) { /* unsuitable CCVal delta */ if (h->rtt_sample_prev == 2) { /* previous candidate stored */ sample = SUB16(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval, tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); if (sample) sample = 4 / sample * ktime_us_delta(tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_tstamp, tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp); else /* * FIXME: This condition is in principle not * possible but occurs when CCID is used for * two-way data traffic. I have tried to trace * it, but the cause does not seem to be here. */ DCCP_BUG("please report to dccp@vger.kernel.org" " => prev = %u, last = %u", tfrc_rx_hist_rtt_prev_s(h)->tfrchrx_ccval, tfrc_rx_hist_rtt_last_s(h)->tfrchrx_ccval); } else if (delta_v < 1) { h->rtt_sample_prev = 1; goto keep_ref_for_next_time; } } else if (delta_v == 4) /* optimal match */ sample = ktime_to_us(net_timedelta(tfrc_rx_hist_rtt_last_s(h)->tfrchrx_tstamp)); else { /* suboptimal match */ h->rtt_sample_prev = 2; goto keep_ref_for_next_time; } if (unlikely(sample > DCCP_SANE_RTT_MAX)) { DCCP_WARN("RTT sample %u too large, using max\n", sample); sample = DCCP_SANE_RTT_MAX; } h->rtt_sample_prev = 0; /* use current entry as next reference */ keep_ref_for_next_time: return sample; }