![Gerrit Renker](/assets/img/avatar_default.png)
This patch brings the Ack Vector interface up to date. Its main purpose is to lay the basis for the subsequent patches of this set, which will use the new data structure fields and routines. There are no real algorithmic changes, rather an adaptation: (1) Replaced the static Ack Vector size (2) with a #define so that it can be adapted (with low loss / Ack Ratio, a value of 1 works, so 2 seems to be sufficient for the moment) and added a solution so that computing the ECN nonce will continue to work - even with larger Ack Vectors. (2) Replaced the #defines for Ack Vector states with a complete enum. (3) Replaced #defines to compute Ack Vector length and state with general purpose routines (inlines), and updated code to use these. (4) Added a `tail' field (conversion to circular buffer in subsequent patch). (5) Updated the (outdated) documentation for Ack Vector struct. (6) All sequence number containers now trimmed to 48 bits. (7) Removal of unused bits: * removed dccpav_ack_nonce from struct dccp_ackvec, since this is already redundantly stored in the `dccpavr_ack_nonce' (of Ack Vector record); * removed Elapsed Time for Ack Vectors (it was nowhere used); * replaced semantics of dccpavr_sent_len with dccpavr_ack_runlen, since the code needs to be able to remember the old run length; * reduced the de-/allocation routines (redundant / duplicate tests). Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
429 lines
12 KiB
C
429 lines
12 KiB
C
/*
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* net/dccp/ackvec.c
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*
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* An implementation of Ack Vectors for the DCCP protocol
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* Copyright (c) 2007 University of Aberdeen, Scotland, UK
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* Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; version 2 of the License;
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*/
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#include "ackvec.h"
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#include "dccp.h"
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#include <linux/init.h>
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#include <linux/errno.h>
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#include <linux/kernel.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <net/sock.h>
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static struct kmem_cache *dccp_ackvec_slab;
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static struct kmem_cache *dccp_ackvec_record_slab;
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struct dccp_ackvec *dccp_ackvec_alloc(const gfp_t priority)
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{
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struct dccp_ackvec *av = kmem_cache_zalloc(dccp_ackvec_slab, priority);
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if (av != NULL) {
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av->av_buf_head = DCCPAV_MAX_ACKVEC_LEN - 1;
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INIT_LIST_HEAD(&av->av_records);
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}
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return av;
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}
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static void dccp_ackvec_purge_records(struct dccp_ackvec *av)
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{
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struct dccp_ackvec_record *cur, *next;
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list_for_each_entry_safe(cur, next, &av->av_records, avr_node)
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kmem_cache_free(dccp_ackvec_record_slab, cur);
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INIT_LIST_HEAD(&av->av_records);
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}
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void dccp_ackvec_free(struct dccp_ackvec *av)
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{
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if (likely(av != NULL)) {
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dccp_ackvec_purge_records(av);
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kmem_cache_free(dccp_ackvec_slab, av);
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}
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}
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static void dccp_ackvec_insert_avr(struct dccp_ackvec *av,
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struct dccp_ackvec_record *avr)
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{
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/*
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* AVRs are sorted by seqno. Since we are sending them in order, we
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* just add the AVR at the head of the list.
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* -sorbo.
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*/
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if (!list_empty(&av->av_records)) {
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const struct dccp_ackvec_record *head =
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list_entry(av->av_records.next,
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struct dccp_ackvec_record,
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avr_node);
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BUG_ON(before48(avr->avr_ack_seqno, head->avr_ack_seqno));
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}
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list_add(&avr->avr_node, &av->av_records);
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}
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int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
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{
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struct dccp_sock *dp = dccp_sk(sk);
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struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
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/* Figure out how many options do we need to represent the ackvec */
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const u8 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_SINGLE_OPT_MAXLEN);
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u16 len = av->av_vec_len + 2 * nr_opts;
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u8 i, nonce = 0;
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const unsigned char *tail, *from;
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unsigned char *to;
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struct dccp_ackvec_record *avr;
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if (DCCP_SKB_CB(skb)->dccpd_opt_len + len > DCCP_MAX_OPT_LEN)
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return -1;
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avr = kmem_cache_alloc(dccp_ackvec_record_slab, GFP_ATOMIC);
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if (avr == NULL)
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return -1;
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DCCP_SKB_CB(skb)->dccpd_opt_len += len;
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to = skb_push(skb, len);
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len = av->av_vec_len;
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from = av->av_buf + av->av_buf_head;
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tail = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
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for (i = 0; i < nr_opts; ++i) {
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int copylen = len;
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if (len > DCCP_SINGLE_OPT_MAXLEN)
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copylen = DCCP_SINGLE_OPT_MAXLEN;
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/*
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* RFC 4340, 12.2: Encode the Nonce Echo for this Ack Vector via
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* its type; ack_nonce is the sum of all individual buf_nonce's.
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*/
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nonce ^= av->av_buf_nonce[i];
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*to++ = DCCPO_ACK_VECTOR_0 + av->av_buf_nonce[i];
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*to++ = copylen + 2;
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/* Check if buf_head wraps */
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if (from + copylen > tail) {
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const u16 tailsize = tail - from;
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memcpy(to, from, tailsize);
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to += tailsize;
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len -= tailsize;
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copylen -= tailsize;
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from = av->av_buf;
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}
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memcpy(to, from, copylen);
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from += copylen;
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to += copylen;
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len -= copylen;
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}
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/*
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* Each sent Ack Vector is recorded in the list, as per A.2 of RFC 4340.
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*/
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avr->avr_ack_seqno = DCCP_SKB_CB(skb)->dccpd_seq;
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avr->avr_ack_ptr = av->av_buf_head;
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avr->avr_ack_ackno = av->av_buf_ackno;
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avr->avr_ack_nonce = nonce;
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avr->avr_ack_runlen = dccp_ackvec_runlen(av->av_buf + av->av_buf_head);
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dccp_ackvec_insert_avr(av, avr);
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dccp_pr_debug("%s ACK Vector 0, len=%d, ack_seqno=%llu, "
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"ack_ackno=%llu\n",
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dccp_role(sk), avr->avr_ack_runlen,
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(unsigned long long)avr->avr_ack_seqno,
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(unsigned long long)avr->avr_ack_ackno);
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return 0;
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}
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/*
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* If several packets are missing, the HC-Receiver may prefer to enter multiple
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* bytes with run length 0, rather than a single byte with a larger run length;
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* this simplifies table updates if one of the missing packets arrives.
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*/
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static inline int dccp_ackvec_set_buf_head_state(struct dccp_ackvec *av,
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const unsigned int packets,
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const unsigned char state)
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{
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long gap;
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long new_head;
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if (av->av_vec_len + packets > DCCPAV_MAX_ACKVEC_LEN)
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return -ENOBUFS;
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gap = packets - 1;
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new_head = av->av_buf_head - packets;
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if (new_head < 0) {
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if (gap > 0) {
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memset(av->av_buf, DCCPAV_NOT_RECEIVED,
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gap + new_head + 1);
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gap = -new_head;
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}
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new_head += DCCPAV_MAX_ACKVEC_LEN;
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}
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av->av_buf_head = new_head;
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if (gap > 0)
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memset(av->av_buf + av->av_buf_head + 1,
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DCCPAV_NOT_RECEIVED, gap);
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av->av_buf[av->av_buf_head] = state;
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av->av_vec_len += packets;
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return 0;
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}
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/*
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* Implements the RFC 4340, Appendix A
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*/
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int dccp_ackvec_add(struct dccp_ackvec *av, const struct sock *sk,
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const u64 ackno, const u8 state)
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{
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u8 *cur_head = av->av_buf + av->av_buf_head,
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*buf_end = av->av_buf + DCCPAV_MAX_ACKVEC_LEN;
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/*
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* Check at the right places if the buffer is full, if it is, tell the
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* caller to start dropping packets till the HC-Sender acks our ACK
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* vectors, when we will free up space in av_buf.
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*
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* We may well decide to do buffer compression, etc, but for now lets
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* just drop.
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*
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* From Appendix A.1.1 (`New Packets'):
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*
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* Of course, the circular buffer may overflow, either when the
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* HC-Sender is sending data at a very high rate, when the
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* HC-Receiver's acknowledgements are not reaching the HC-Sender,
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* or when the HC-Sender is forgetting to acknowledge those acks
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* (so the HC-Receiver is unable to clean up old state). In this
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* case, the HC-Receiver should either compress the buffer (by
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* increasing run lengths when possible), transfer its state to
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* a larger buffer, or, as a last resort, drop all received
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* packets, without processing them whatsoever, until its buffer
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* shrinks again.
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*/
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/* See if this is the first ackno being inserted */
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if (av->av_vec_len == 0) {
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*cur_head = state;
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av->av_vec_len = 1;
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} else if (after48(ackno, av->av_buf_ackno)) {
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const u64 delta = dccp_delta_seqno(av->av_buf_ackno, ackno);
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/*
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* Look if the state of this packet is the same as the
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* previous ackno and if so if we can bump the head len.
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*/
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if (delta == 1 && dccp_ackvec_state(cur_head) == state &&
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dccp_ackvec_runlen(cur_head) < DCCPAV_MAX_RUNLEN)
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*cur_head += 1;
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else if (dccp_ackvec_set_buf_head_state(av, delta, state))
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return -ENOBUFS;
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} else {
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/*
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* A.1.2. Old Packets
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*
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* When a packet with Sequence Number S <= buf_ackno
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* arrives, the HC-Receiver will scan the table for
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* the byte corresponding to S. (Indexing structures
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* could reduce the complexity of this scan.)
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*/
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u64 delta = dccp_delta_seqno(ackno, av->av_buf_ackno);
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while (1) {
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const u8 len = dccp_ackvec_runlen(cur_head);
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/*
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* valid packets not yet in av_buf have a reserved
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* entry, with a len equal to 0.
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*/
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if (*cur_head == DCCPAV_NOT_RECEIVED && delta == 0) {
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dccp_pr_debug("Found %llu reserved seat!\n",
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(unsigned long long)ackno);
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*cur_head = state;
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goto out;
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}
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/* len == 0 means one packet */
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if (delta < len + 1)
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goto out_duplicate;
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delta -= len + 1;
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if (++cur_head == buf_end)
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cur_head = av->av_buf;
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}
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}
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av->av_buf_ackno = ackno;
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out:
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return 0;
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out_duplicate:
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/* Duplicate packet */
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dccp_pr_debug("Received a dup or already considered lost "
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"packet: %llu\n", (unsigned long long)ackno);
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return -EILSEQ;
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}
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static void dccp_ackvec_throw_record(struct dccp_ackvec *av,
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struct dccp_ackvec_record *avr)
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{
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struct dccp_ackvec_record *next;
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/* sort out vector length */
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if (av->av_buf_head <= avr->avr_ack_ptr)
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av->av_vec_len = avr->avr_ack_ptr - av->av_buf_head;
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else
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av->av_vec_len = DCCPAV_MAX_ACKVEC_LEN - 1 -
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av->av_buf_head + avr->avr_ack_ptr;
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/* free records */
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list_for_each_entry_safe_from(avr, next, &av->av_records, avr_node) {
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list_del(&avr->avr_node);
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kmem_cache_free(dccp_ackvec_record_slab, avr);
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}
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}
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void dccp_ackvec_check_rcv_ackno(struct dccp_ackvec *av, struct sock *sk,
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const u64 ackno)
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{
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struct dccp_ackvec_record *avr;
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/*
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* If we traverse backwards, it should be faster when we have large
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* windows. We will be receiving ACKs for stuff we sent a while back
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* -sorbo.
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*/
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list_for_each_entry_reverse(avr, &av->av_records, avr_node) {
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if (ackno == avr->avr_ack_seqno) {
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dccp_pr_debug("%s ACK packet 0, len=%d, ack_seqno=%llu, "
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"ack_ackno=%llu, ACKED!\n",
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dccp_role(sk), avr->avr_ack_runlen,
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(unsigned long long)avr->avr_ack_seqno,
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(unsigned long long)avr->avr_ack_ackno);
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dccp_ackvec_throw_record(av, avr);
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break;
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} else if (avr->avr_ack_seqno > ackno)
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break; /* old news */
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}
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}
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static void dccp_ackvec_check_rcv_ackvector(struct dccp_ackvec *av,
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struct sock *sk, u64 *ackno,
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const unsigned char len,
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const unsigned char *vector)
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{
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unsigned char i;
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struct dccp_ackvec_record *avr;
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/* Check if we actually sent an ACK vector */
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if (list_empty(&av->av_records))
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return;
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i = len;
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/*
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* XXX
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* I think it might be more efficient to work backwards. See comment on
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* rcv_ackno. -sorbo.
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*/
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avr = list_entry(av->av_records.next, struct dccp_ackvec_record, avr_node);
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while (i--) {
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const u8 rl = dccp_ackvec_runlen(vector);
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u64 ackno_end_rl;
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dccp_set_seqno(&ackno_end_rl, *ackno - rl);
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/*
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* If our AVR sequence number is greater than the ack, go
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* forward in the AVR list until it is not so.
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*/
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list_for_each_entry_from(avr, &av->av_records, avr_node) {
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if (!after48(avr->avr_ack_seqno, *ackno))
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goto found;
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}
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/* End of the av_records list, not found, exit */
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break;
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found:
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if (between48(avr->avr_ack_seqno, ackno_end_rl, *ackno)) {
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if (dccp_ackvec_state(vector) != DCCPAV_NOT_RECEIVED) {
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dccp_pr_debug("%s ACK vector 0, len=%d, "
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"ack_seqno=%llu, ack_ackno=%llu, "
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"ACKED!\n",
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dccp_role(sk), len,
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(unsigned long long)
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avr->avr_ack_seqno,
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(unsigned long long)
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avr->avr_ack_ackno);
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dccp_ackvec_throw_record(av, avr);
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break;
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}
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/*
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* If it wasn't received, continue scanning... we might
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* find another one.
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*/
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}
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dccp_set_seqno(ackno, ackno_end_rl - 1);
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++vector;
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}
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}
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int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
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u64 *ackno, const u8 opt, const u8 *value, const u8 len)
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{
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if (len > DCCP_SINGLE_OPT_MAXLEN)
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return -1;
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/* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
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dccp_ackvec_check_rcv_ackvector(dccp_sk(sk)->dccps_hc_rx_ackvec, sk,
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ackno, len, value);
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return 0;
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}
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int __init dccp_ackvec_init(void)
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{
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dccp_ackvec_slab = kmem_cache_create("dccp_ackvec",
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sizeof(struct dccp_ackvec), 0,
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SLAB_HWCACHE_ALIGN, NULL);
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if (dccp_ackvec_slab == NULL)
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goto out_err;
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dccp_ackvec_record_slab = kmem_cache_create("dccp_ackvec_record",
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sizeof(struct dccp_ackvec_record),
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0, SLAB_HWCACHE_ALIGN, NULL);
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if (dccp_ackvec_record_slab == NULL)
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goto out_destroy_slab;
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return 0;
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out_destroy_slab:
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kmem_cache_destroy(dccp_ackvec_slab);
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dccp_ackvec_slab = NULL;
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out_err:
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DCCP_CRIT("Unable to create Ack Vector slab cache");
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return -ENOBUFS;
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}
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void dccp_ackvec_exit(void)
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{
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if (dccp_ackvec_slab != NULL) {
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kmem_cache_destroy(dccp_ackvec_slab);
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dccp_ackvec_slab = NULL;
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}
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if (dccp_ackvec_record_slab != NULL) {
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kmem_cache_destroy(dccp_ackvec_record_slab);
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dccp_ackvec_record_slab = NULL;
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}
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}
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