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kernel-hacking-2024-linux-s.../net/tipc/link.h
Jon Paul Maloy c637c10355 tipc: resolve race problem at unicast message reception 
TIPC handles message cardinality and sequencing at the link layer,
before passing messages upwards to the destination sockets. During the
upcall from link to socket no locks are held. It is therefore possible,
and we see it happen occasionally, that messages arriving in different
threads and delivered in sequence still bypass each other before they
reach the destination socket. This must not happen, since it violates
the sequentiality guarantee.

We solve this by adding a new input buffer queue to the link structure.
Arriving messages are added safely to the tail of that queue by the
link, while the head of the queue is consumed, also safely, by the
receiving socket. Sequentiality is secured per socket by only allowing
buffers to be dequeued inside the socket lock. Since there may be multiple
simultaneous readers of the queue, we use a 'filter' parameter to reduce
the risk that they peek the same buffer from the queue, hence also
reducing the risk of contention on the receiving socket locks.

This solves the sequentiality problem, and seems to cause no measurable
performance degradation.

A nice side effect of this change is that lock handling in the functions
tipc_rcv() and tipc_bcast_rcv() now becomes uniform, something that
will enable future simplifications of those functions.

Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-02-05 16:00:02 -08:00

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/*
* net/tipc/link.h: Include file for TIPC link code
*
* Copyright (c) 1995-2006, 2013-2014, Ericsson AB
* Copyright (c) 2004-2005, 2010-2011, Wind River Systems
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the names of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _TIPC_LINK_H
#define _TIPC_LINK_H
#include <net/genetlink.h>
#include "msg.h"
#include "node.h"
/* TIPC-specific error codes
*/
#define ELINKCONG EAGAIN /* link congestion <=> resource unavailable */
/* Out-of-range value for link sequence numbers
*/
#define INVALID_LINK_SEQ 0x10000
/* Link working states
*/
#define WORKING_WORKING 560810u
#define WORKING_UNKNOWN 560811u
#define RESET_UNKNOWN 560812u
#define RESET_RESET 560813u
/* Link endpoint execution states
*/
#define LINK_STARTED 0x0001
#define LINK_STOPPED 0x0002
/* Starting value for maximum packet size negotiation on unicast links
* (unless bearer MTU is less)
*/
#define MAX_PKT_DEFAULT 1500
struct tipc_stats {
u32 sent_info; /* used in counting # sent packets */
u32 recv_info; /* used in counting # recv'd packets */
u32 sent_states;
u32 recv_states;
u32 sent_probes;
u32 recv_probes;
u32 sent_nacks;
u32 recv_nacks;
u32 sent_acks;
u32 sent_bundled;
u32 sent_bundles;
u32 recv_bundled;
u32 recv_bundles;
u32 retransmitted;
u32 sent_fragmented;
u32 sent_fragments;
u32 recv_fragmented;
u32 recv_fragments;
u32 link_congs; /* # port sends blocked by congestion */
u32 deferred_recv;
u32 duplicates;
u32 max_queue_sz; /* send queue size high water mark */
u32 accu_queue_sz; /* used for send queue size profiling */
u32 queue_sz_counts; /* used for send queue size profiling */
u32 msg_length_counts; /* used for message length profiling */
u32 msg_lengths_total; /* used for message length profiling */
u32 msg_length_profile[7]; /* used for msg. length profiling */
};
/**
* struct tipc_link - TIPC link data structure
* @addr: network address of link's peer node
* @name: link name character string
* @media_addr: media address to use when sending messages over link
* @timer: link timer
* @owner: pointer to peer node
* @refcnt: reference counter for permanent references (owner node & timer)
* @flags: execution state flags for link endpoint instance
* @checkpoint: reference point for triggering link continuity checking
* @peer_session: link session # being used by peer end of link
* @peer_bearer_id: bearer id used by link's peer endpoint
* @bearer_id: local bearer id used by link
* @tolerance: minimum link continuity loss needed to reset link [in ms]
* @cont_intv: link continuity testing interval
* @abort_limit: # of unacknowledged continuity probes needed to reset link
* @state: current state of link FSM
* @fsm_msg_cnt: # of protocol messages link FSM has sent in current state
* @proto_msg: template for control messages generated by link
* @pmsg: convenience pointer to "proto_msg" field
* @priority: current link priority
* @net_plane: current link network plane ('A' through 'H')
* @queue_limit: outbound message queue congestion thresholds (indexed by user)
* @exp_msg_count: # of tunnelled messages expected during link changeover
* @reset_checkpoint: seq # of last acknowledged message at time of link reset
* @max_pkt: current maximum packet size for this link
* @max_pkt_target: desired maximum packet size for this link
* @max_pkt_probes: # of probes based on current (max_pkt, max_pkt_target)
* @outqueue: outbound message queue
* @next_out_no: next sequence number to use for outbound messages
* @last_retransmitted: sequence number of most recently retransmitted message
* @stale_count: # of identical retransmit requests made by peer
* @next_in_no: next sequence number to expect for inbound messages
* @deferred_queue: deferred queue saved OOS b'cast message received from node
* @unacked_window: # of inbound messages rx'd without ack'ing back to peer
* @inputq: buffer queue for messages to be delivered upwards
* @namedq: buffer queue for name table messages to be delivered upwards
* @next_out: ptr to first unsent outbound message in queue
* @wakeupq: linked list of wakeup msgs waiting for link congestion to abate
* @long_msg_seq_no: next identifier to use for outbound fragmented messages
* @reasm_buf: head of partially reassembled inbound message fragments
* @stats: collects statistics regarding link activity
*/
struct tipc_link {
u32 addr;
char name[TIPC_MAX_LINK_NAME];
struct tipc_media_addr media_addr;
struct timer_list timer;
struct tipc_node *owner;
struct kref ref;
/* Management and link supervision data */
unsigned int flags;
u32 checkpoint;
u32 peer_session;
u32 peer_bearer_id;
u32 bearer_id;
u32 tolerance;
unsigned long cont_intv;
u32 abort_limit;
int state;
u32 fsm_msg_cnt;
struct {
unchar hdr[INT_H_SIZE];
unchar body[TIPC_MAX_IF_NAME];
} proto_msg;
struct tipc_msg *pmsg;
u32 priority;
char net_plane;
u32 queue_limit[15]; /* queue_limit[0]==window limit */
/* Changeover */
u32 exp_msg_count;
u32 reset_checkpoint;
/* Max packet negotiation */
u32 max_pkt;
u32 max_pkt_target;
u32 max_pkt_probes;
/* Sending */
struct sk_buff_head outqueue;
u32 next_out_no;
u32 last_retransmitted;
u32 stale_count;
/* Reception */
u32 next_in_no;
struct sk_buff_head deferred_queue;
u32 unacked_window;
struct sk_buff_head inputq;
struct sk_buff_head namedq;
/* Congestion handling */
struct sk_buff *next_out;
struct sk_buff_head wakeupq;
/* Fragmentation/reassembly */
u32 long_msg_seq_no;
struct sk_buff *reasm_buf;
/* Statistics */
struct tipc_stats stats;
};
struct tipc_port;
struct tipc_link *tipc_link_create(struct tipc_node *n_ptr,
struct tipc_bearer *b_ptr,
const struct tipc_media_addr *media_addr);
void tipc_link_delete(struct tipc_link *link);
void tipc_link_delete_list(struct net *net, unsigned int bearer_id,
bool shutting_down);
void tipc_link_failover_send_queue(struct tipc_link *l_ptr);
void tipc_link_dup_queue_xmit(struct tipc_link *l_ptr, struct tipc_link *dest);
void tipc_link_reset_fragments(struct tipc_link *l_ptr);
int tipc_link_is_up(struct tipc_link *l_ptr);
int tipc_link_is_active(struct tipc_link *l_ptr);
void tipc_link_purge_queues(struct tipc_link *l_ptr);
struct sk_buff *tipc_link_cmd_config(struct net *net, const void *req_tlv_area,
int req_tlv_space, u16 cmd);
struct sk_buff *tipc_link_cmd_show_stats(struct net *net,
const void *req_tlv_area,
int req_tlv_space);
struct sk_buff *tipc_link_cmd_reset_stats(struct net *net,
const void *req_tlv_area,
int req_tlv_space);
void tipc_link_reset_all(struct tipc_node *node);
void tipc_link_reset(struct tipc_link *l_ptr);
void tipc_link_reset_list(struct net *net, unsigned int bearer_id);
int tipc_link_xmit_skb(struct net *net, struct sk_buff *skb, u32 dest,
u32 selector);
int tipc_link_xmit(struct net *net, struct sk_buff_head *list, u32 dest,
u32 selector);
int __tipc_link_xmit(struct net *net, struct tipc_link *link,
struct sk_buff_head *list);
void tipc_link_proto_xmit(struct tipc_link *l_ptr, u32 msg_typ, int prob,
u32 gap, u32 tolerance, u32 priority, u32 acked_mtu);
void tipc_link_push_packets(struct tipc_link *l_ptr);
u32 tipc_link_defer_pkt(struct sk_buff_head *list, struct sk_buff *buf);
void tipc_link_set_queue_limits(struct tipc_link *l_ptr, u32 window);
void tipc_link_retransmit(struct tipc_link *l_ptr,
struct sk_buff *start, u32 retransmits);
struct sk_buff *tipc_skb_queue_next(const struct sk_buff_head *list,
const struct sk_buff *skb);
int tipc_nl_link_dump(struct sk_buff *skb, struct netlink_callback *cb);
int tipc_nl_link_get(struct sk_buff *skb, struct genl_info *info);
int tipc_nl_link_set(struct sk_buff *skb, struct genl_info *info);
int tipc_nl_link_reset_stats(struct sk_buff *skb, struct genl_info *info);
int tipc_nl_parse_link_prop(struct nlattr *prop, struct nlattr *props[]);
void link_prepare_wakeup(struct tipc_link *l);
/*
* Link sequence number manipulation routines (uses modulo 2**16 arithmetic)
*/
static inline u32 buf_seqno(struct sk_buff *buf)
{
return msg_seqno(buf_msg(buf));
}
static inline u32 mod(u32 x)
{
return x & 0xffffu;
}
static inline int less_eq(u32 left, u32 right)
{
return mod(right - left) < 32768u;
}
static inline int more(u32 left, u32 right)
{
return !less_eq(left, right);
}
static inline int less(u32 left, u32 right)
{
return less_eq(left, right) && (mod(right) != mod(left));
}
static inline u32 lesser(u32 left, u32 right)
{
return less_eq(left, right) ? left : right;
}
static inline u32 link_own_addr(struct tipc_link *l)
{
return msg_prevnode(l->pmsg);
}
/*
* Link status checking routines
*/
static inline int link_working_working(struct tipc_link *l_ptr)
{
return l_ptr->state == WORKING_WORKING;
}
static inline int link_working_unknown(struct tipc_link *l_ptr)
{
return l_ptr->state == WORKING_UNKNOWN;
}
static inline int link_reset_unknown(struct tipc_link *l_ptr)
{
return l_ptr->state == RESET_UNKNOWN;
}
static inline int link_reset_reset(struct tipc_link *l_ptr)
{
return l_ptr->state == RESET_RESET;
}
static inline int link_congested(struct tipc_link *l_ptr)
{
return skb_queue_len(&l_ptr->outqueue) >= l_ptr->queue_limit[0];
}
#endif
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