osmo-pcu/src/llc.h

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/*
* Copyright (C) 2013 by Holger Hans Peter Freyther
*
* 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#pragma once
#ifdef __cplusplus
extern "C" {
#endif
#include <osmocom/core/linuxlist.h>
#ifdef __cplusplus
}
#endif
#include <stdint.h>
#include <string.h>
#include <time.h>
#define LLC_MAX_LEN 1543
struct gprs_rlcmac_bts;
/**
* I represent the LLC data to a MS
*/
struct gprs_llc {
#ifdef __cplusplus
tbf: Use a hysteresis when discarding DL LLC frames Currently single LLC blocks are discarded when the PDU lifetime expires. If an IP packet has been fragmented either on the IP or on the LLC layer and is therefore distributed over several LLC frames, the kept fragments are transmitted and then discarded by the MS because of the missing PDU. This can cause massive IP packet loss when there are many fragmented packets (e.g. when trying 'ping -s1800' or if the GGSN chops downlink IP packets into several SNDCP packets). On the other hand, discarding too many packets might disturb the congestion handling of TCP. Dropping plain TCP ACKs might also hinder flow control and congestion avoidance. This commit adds a hysteresis algorithm to the LLC discard loop. If an LLC message's age reaches the high water mark, further message's with an age above the low water mark are discarded, too. This is aborted, if a GMM, a non-UI, or a small message is detected. In these cases, that message is kept. The following VTY commands are added (pcu config node): - queue hysteresis <1-65535> set the difference between high (lifetime) and low watermark in centiseconds - no queue hysteresis disable this feature (default) Since the SGSN will most probably send all fragments of a single N-PDU without much delay between them, a value slightly above the average transmission delay jitter between SGSN and PCU is probably a sensible value to discard all fragments of a single IP packet. This is an experimental feature that might be replaced by more advanced means of active queue management in the future. Sponsored-by: On-Waves ehf
2015-03-20 11:02:42 +00:00
static bool is_user_data_frame(uint8_t *data, size_t len);
void init();
void reset();
void reset_frame_space();
void put_frame(const uint8_t *data, size_t len);
void put_dummy_frame(size_t req_len);
void append_frame(const uint8_t *data, size_t len);
#endif
uint8_t frame[LLC_MAX_LEN]; /* current DL or UL frame */
uint16_t m_index; /* current write/read position of frame */
uint16_t m_length; /* len of current DL LLC_frame, 0 == no frame */
};
struct MetaInfo {
struct timespec recv_time;
struct timespec expire_time;
};
/**
* I store the LLC frames that come from the SGSN.
*/
struct gprs_llc_queue {
#ifdef __cplusplus
static void calc_pdu_lifetime(struct gprs_rlcmac_bts *bts, const uint16_t pdu_delay_csec,
struct timespec *tv);
static bool is_frame_expired(const struct timespec *now,
const struct timespec *tv);
static bool is_user_data_frame(uint8_t *data, size_t len);
void enqueue(struct msgb *llc_msg, const struct timespec *expire_time);
struct msgb *dequeue(const MetaInfo **info = 0);
#endif
uint32_t m_avg_queue_delay; /* Average delay of data going through the queue */
size_t m_queue_size;
size_t m_queue_octets;
struct llist_head m_queue; /* queued LLC DL data */
};
#ifdef __cplusplus
extern "C" {
#endif
void llc_queue_init(struct gprs_llc_queue *q);
void llc_queue_clear(struct gprs_llc_queue *q, struct gprs_rlcmac_bts *bts);
void llc_queue_move_and_merge(struct gprs_llc_queue *q, struct gprs_llc_queue *o);
static inline uint16_t llc_chunk_size(const struct gprs_llc *llc)
{
return llc->m_length - llc->m_index;
}
static inline uint16_t llc_remaining_space(const struct gprs_llc *llc)
{
return LLC_MAX_LEN - llc->m_length;
}
static inline uint16_t llc_frame_length(const struct gprs_llc *llc)
{
return llc->m_length;
}
static inline void llc_consume(struct gprs_llc *llc, size_t len)
{
llc->m_index += len;
}
static inline void llc_consume_data(struct gprs_llc *llc, uint8_t *data, size_t len)
{
/* copy and increment index */
memcpy(data, llc->frame + llc->m_index, len);
llc_consume(llc, len);
}
static inline bool llc_fits_in_current_frame(const struct gprs_llc *llc, uint8_t chunk_size)
{
return llc->m_length + chunk_size <= LLC_MAX_LEN;
}
static inline size_t llc_queue_size(const struct gprs_llc_queue *q)
{
return q->m_queue_size;
}
static inline size_t llc_queue_octets(const struct gprs_llc_queue *q)
{
return q->m_queue_octets;
}
#ifdef __cplusplus
}
#endif