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linux/net/tipc/msg.h
Jon Paul Maloy cb1b728096 tipc: eliminate race condition at multicast reception 
In a previous commit in this series we resolved a race problem during
unicast message reception.

Here, we resolve the same problem at multicast reception. We apply the
same technique: an input queue serializing the delivery of arriving
buffers. The main difference is that here we do it in two steps.
First, the broadcast link feeds arriving buffers into the tail of an
arrival queue, which head is consumed at the socket level, and where
destination lookup is performed. Second, if the lookup is successful,
the resulting buffer clones are fed into a second queue, the input
queue. This queue is consumed at reception in the socket just like
in the unicast case. Both queues are protected by the same lock, -the
one of the input queue.

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 16:00:03 -08:00

859 lines
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/*
* net/tipc/msg.h: Include file for TIPC message header routines
*
* Copyright (c) 2000-2007, 2014, Ericsson AB
* Copyright (c) 2005-2008, 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_MSG_H
#define _TIPC_MSG_H
#include <linux/tipc.h>
/*
* Constants and routines used to read and write TIPC payload message headers
*
* Note: Some items are also used with TIPC internal message headers
*/
#define TIPC_VERSION 2
struct plist;
/*
* Payload message users are defined in TIPC's public API:
* - TIPC_LOW_IMPORTANCE
* - TIPC_MEDIUM_IMPORTANCE
* - TIPC_HIGH_IMPORTANCE
* - TIPC_CRITICAL_IMPORTANCE
*/
/*
* Payload message types
*/
#define TIPC_CONN_MSG 0
#define TIPC_MCAST_MSG 1
#define TIPC_NAMED_MSG 2
#define TIPC_DIRECT_MSG 3
/*
* Message header sizes
*/
#define SHORT_H_SIZE 24 /* In-cluster basic payload message */
#define BASIC_H_SIZE 32 /* Basic payload message */
#define NAMED_H_SIZE 40 /* Named payload message */
#define MCAST_H_SIZE 44 /* Multicast payload message */
#define INT_H_SIZE 40 /* Internal messages */
#define MIN_H_SIZE 24 /* Smallest legal TIPC header size */
#define MAX_H_SIZE 60 /* Largest possible TIPC header size */
#define MAX_MSG_SIZE (MAX_H_SIZE + TIPC_MAX_USER_MSG_SIZE)
#define TIPC_MEDIA_ADDR_OFFSET 5
/**
* TIPC message buffer code
*
* TIPC message buffer headroom reserves space for the worst-case
* link-level device header (in case the message is sent off-node).
*
* Note: Headroom should be a multiple of 4 to ensure the TIPC header fields
* are word aligned for quicker access
*/
#define BUF_HEADROOM LL_MAX_HEADER
struct tipc_skb_cb {
void *handle;
struct sk_buff *tail;
bool deferred;
bool wakeup_pending;
bool bundling;
u16 chain_sz;
u16 chain_imp;
};
#define TIPC_SKB_CB(__skb) ((struct tipc_skb_cb *)&((__skb)->cb[0]))
struct tipc_msg {
__be32 hdr[15];
};
static inline struct tipc_msg *buf_msg(struct sk_buff *skb)
{
return (struct tipc_msg *)skb->data;
}
static inline u32 msg_word(struct tipc_msg *m, u32 pos)
{
return ntohl(m->hdr[pos]);
}
static inline void msg_set_word(struct tipc_msg *m, u32 w, u32 val)
{
m->hdr[w] = htonl(val);
}
static inline u32 msg_bits(struct tipc_msg *m, u32 w, u32 pos, u32 mask)
{
return (msg_word(m, w) >> pos) & mask;
}
static inline void msg_set_bits(struct tipc_msg *m, u32 w,
u32 pos, u32 mask, u32 val)
{
val = (val & mask) << pos;
mask = mask << pos;
m->hdr[w] &= ~htonl(mask);
m->hdr[w] |= htonl(val);
}
static inline void msg_swap_words(struct tipc_msg *msg, u32 a, u32 b)
{
u32 temp = msg->hdr[a];
msg->hdr[a] = msg->hdr[b];
msg->hdr[b] = temp;
}
/*
* Word 0
*/
static inline u32 msg_version(struct tipc_msg *m)
{
return msg_bits(m, 0, 29, 7);
}
static inline void msg_set_version(struct tipc_msg *m)
{
msg_set_bits(m, 0, 29, 7, TIPC_VERSION);
}
static inline u32 msg_user(struct tipc_msg *m)
{
return msg_bits(m, 0, 25, 0xf);
}
static inline u32 msg_isdata(struct tipc_msg *m)
{
return msg_user(m) <= TIPC_CRITICAL_IMPORTANCE;
}
static inline void msg_set_user(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 0, 25, 0xf, n);
}
static inline u32 msg_importance(struct tipc_msg *m)
{
return msg_bits(m, 0, 25, 0xf);
}
static inline void msg_set_importance(struct tipc_msg *m, u32 i)
{
msg_set_user(m, i);
}
static inline u32 msg_hdr_sz(struct tipc_msg *m)
{
return msg_bits(m, 0, 21, 0xf) << 2;
}
static inline void msg_set_hdr_sz(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 0, 21, 0xf, n>>2);
}
static inline u32 msg_size(struct tipc_msg *m)
{
return msg_bits(m, 0, 0, 0x1ffff);
}
static inline u32 msg_data_sz(struct tipc_msg *m)
{
return msg_size(m) - msg_hdr_sz(m);
}
static inline int msg_non_seq(struct tipc_msg *m)
{
return msg_bits(m, 0, 20, 1);
}
static inline void msg_set_non_seq(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 0, 20, 1, n);
}
static inline int msg_dest_droppable(struct tipc_msg *m)
{
return msg_bits(m, 0, 19, 1);
}
static inline void msg_set_dest_droppable(struct tipc_msg *m, u32 d)
{
msg_set_bits(m, 0, 19, 1, d);
}
static inline int msg_src_droppable(struct tipc_msg *m)
{
return msg_bits(m, 0, 18, 1);
}
static inline void msg_set_src_droppable(struct tipc_msg *m, u32 d)
{
msg_set_bits(m, 0, 18, 1, d);
}
static inline void msg_set_size(struct tipc_msg *m, u32 sz)
{
m->hdr[0] = htonl((msg_word(m, 0) & ~0x1ffff) | sz);
}
/*
* Word 1
*/
static inline u32 msg_type(struct tipc_msg *m)
{
return msg_bits(m, 1, 29, 0x7);
}
static inline void msg_set_type(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 1, 29, 0x7, n);
}
static inline u32 msg_named(struct tipc_msg *m)
{
return msg_type(m) == TIPC_NAMED_MSG;
}
static inline u32 msg_mcast(struct tipc_msg *m)
{
return msg_type(m) == TIPC_MCAST_MSG;
}
static inline u32 msg_connected(struct tipc_msg *m)
{
return msg_type(m) == TIPC_CONN_MSG;
}
static inline u32 msg_errcode(struct tipc_msg *m)
{
return msg_bits(m, 1, 25, 0xf);
}
static inline void msg_set_errcode(struct tipc_msg *m, u32 err)
{
msg_set_bits(m, 1, 25, 0xf, err);
}
static inline u32 msg_reroute_cnt(struct tipc_msg *m)
{
return msg_bits(m, 1, 21, 0xf);
}
static inline void msg_incr_reroute_cnt(struct tipc_msg *m)
{
msg_set_bits(m, 1, 21, 0xf, msg_reroute_cnt(m) + 1);
}
static inline void msg_reset_reroute_cnt(struct tipc_msg *m)
{
msg_set_bits(m, 1, 21, 0xf, 0);
}
static inline u32 msg_lookup_scope(struct tipc_msg *m)
{
return msg_bits(m, 1, 19, 0x3);
}
static inline void msg_set_lookup_scope(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 1, 19, 0x3, n);
}
static inline u32 msg_bcast_ack(struct tipc_msg *m)
{
return msg_bits(m, 1, 0, 0xffff);
}
static inline void msg_set_bcast_ack(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 1, 0, 0xffff, n);
}
/*
* Word 2
*/
static inline u32 msg_ack(struct tipc_msg *m)
{
return msg_bits(m, 2, 16, 0xffff);
}
static inline void msg_set_ack(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 2, 16, 0xffff, n);
}
static inline u32 msg_seqno(struct tipc_msg *m)
{
return msg_bits(m, 2, 0, 0xffff);
}
static inline void msg_set_seqno(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 2, 0, 0xffff, n);
}
/*
* Words 3-10
*/
static inline u32 msg_prevnode(struct tipc_msg *m)
{
return msg_word(m, 3);
}
static inline void msg_set_prevnode(struct tipc_msg *m, u32 a)
{
msg_set_word(m, 3, a);
}
static inline u32 msg_origport(struct tipc_msg *m)
{
return msg_word(m, 4);
}
static inline void msg_set_origport(struct tipc_msg *m, u32 p)
{
msg_set_word(m, 4, p);
}
static inline u32 msg_destport(struct tipc_msg *m)
{
return msg_word(m, 5);
}
static inline void msg_set_destport(struct tipc_msg *m, u32 p)
{
msg_set_word(m, 5, p);
}
static inline u32 msg_mc_netid(struct tipc_msg *m)
{
return msg_word(m, 5);
}
static inline void msg_set_mc_netid(struct tipc_msg *m, u32 p)
{
msg_set_word(m, 5, p);
}
static inline int msg_short(struct tipc_msg *m)
{
return msg_hdr_sz(m) == SHORT_H_SIZE;
}
static inline u32 msg_orignode(struct tipc_msg *m)
{
if (likely(msg_short(m)))
return msg_prevnode(m);
return msg_word(m, 6);
}
static inline void msg_set_orignode(struct tipc_msg *m, u32 a)
{
msg_set_word(m, 6, a);
}
static inline u32 msg_destnode(struct tipc_msg *m)
{
return msg_word(m, 7);
}
static inline void msg_set_destnode(struct tipc_msg *m, u32 a)
{
msg_set_word(m, 7, a);
}
static inline u32 msg_nametype(struct tipc_msg *m)
{
return msg_word(m, 8);
}
static inline void msg_set_nametype(struct tipc_msg *m, u32 n)
{
msg_set_word(m, 8, n);
}
static inline u32 msg_nameinst(struct tipc_msg *m)
{
return msg_word(m, 9);
}
static inline u32 msg_namelower(struct tipc_msg *m)
{
return msg_nameinst(m);
}
static inline void msg_set_namelower(struct tipc_msg *m, u32 n)
{
msg_set_word(m, 9, n);
}
static inline void msg_set_nameinst(struct tipc_msg *m, u32 n)
{
msg_set_namelower(m, n);
}
static inline u32 msg_nameupper(struct tipc_msg *m)
{
return msg_word(m, 10);
}
static inline void msg_set_nameupper(struct tipc_msg *m, u32 n)
{
msg_set_word(m, 10, n);
}
static inline unchar *msg_data(struct tipc_msg *m)
{
return ((unchar *)m) + msg_hdr_sz(m);
}
static inline struct tipc_msg *msg_get_wrapped(struct tipc_msg *m)
{
return (struct tipc_msg *)msg_data(m);
}
/*
* Constants and routines used to read and write TIPC internal message headers
*/
/*
* Internal message users
*/
#define BCAST_PROTOCOL 5
#define MSG_BUNDLER 6
#define LINK_PROTOCOL 7
#define CONN_MANAGER 8
#define ROUTE_DISTRIBUTOR 9 /* obsoleted */
#define CHANGEOVER_PROTOCOL 10
#define NAME_DISTRIBUTOR 11
#define MSG_FRAGMENTER 12
#define LINK_CONFIG 13
#define SOCK_WAKEUP 14 /* pseudo user */
/*
* Connection management protocol message types
*/
#define CONN_PROBE 0
#define CONN_PROBE_REPLY 1
#define CONN_ACK 2
/*
* Name distributor message types
*/
#define PUBLICATION 0
#define WITHDRAWAL 1
/*
* Segmentation message types
*/
#define FIRST_FRAGMENT 0
#define FRAGMENT 1
#define LAST_FRAGMENT 2
/*
* Link management protocol message types
*/
#define STATE_MSG 0
#define RESET_MSG 1
#define ACTIVATE_MSG 2
/*
* Changeover tunnel message types
*/
#define DUPLICATE_MSG 0
#define ORIGINAL_MSG 1
/*
* Config protocol message types
*/
#define DSC_REQ_MSG 0
#define DSC_RESP_MSG 1
/*
* Word 1
*/
static inline u32 msg_seq_gap(struct tipc_msg *m)
{
return msg_bits(m, 1, 16, 0x1fff);
}
static inline void msg_set_seq_gap(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 1, 16, 0x1fff, n);
}
static inline u32 msg_node_sig(struct tipc_msg *m)
{
return msg_bits(m, 1, 0, 0xffff);
}
static inline void msg_set_node_sig(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 1, 0, 0xffff, n);
}
/*
* Word 2
*/
static inline u32 msg_dest_domain(struct tipc_msg *m)
{
return msg_word(m, 2);
}
static inline void msg_set_dest_domain(struct tipc_msg *m, u32 n)
{
msg_set_word(m, 2, n);
}
static inline u32 msg_bcgap_after(struct tipc_msg *m)
{
return msg_bits(m, 2, 16, 0xffff);
}
static inline void msg_set_bcgap_after(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 2, 16, 0xffff, n);
}
static inline u32 msg_bcgap_to(struct tipc_msg *m)
{
return msg_bits(m, 2, 0, 0xffff);
}
static inline void msg_set_bcgap_to(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 2, 0, 0xffff, n);
}
/*
* Word 4
*/
static inline u32 msg_last_bcast(struct tipc_msg *m)
{
return msg_bits(m, 4, 16, 0xffff);
}
static inline void msg_set_last_bcast(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 4, 16, 0xffff, n);
}
static inline void msg_set_fragm_no(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 4, 16, 0xffff, n);
}
static inline u32 msg_next_sent(struct tipc_msg *m)
{
return msg_bits(m, 4, 0, 0xffff);
}
static inline void msg_set_next_sent(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 4, 0, 0xffff, n);
}
static inline void msg_set_long_msgno(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 4, 0, 0xffff, n);
}
static inline u32 msg_bc_netid(struct tipc_msg *m)
{
return msg_word(m, 4);
}
static inline void msg_set_bc_netid(struct tipc_msg *m, u32 id)
{
msg_set_word(m, 4, id);
}
static inline u32 msg_link_selector(struct tipc_msg *m)
{
return msg_bits(m, 4, 0, 1);
}
static inline void msg_set_link_selector(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 4, 0, 1, n);
}
/*
* Word 5
*/
static inline u32 msg_session(struct tipc_msg *m)
{
return msg_bits(m, 5, 16, 0xffff);
}
static inline void msg_set_session(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 5, 16, 0xffff, n);
}
static inline u32 msg_probe(struct tipc_msg *m)
{
return msg_bits(m, 5, 0, 1);
}
static inline void msg_set_probe(struct tipc_msg *m, u32 val)
{
msg_set_bits(m, 5, 0, 1, val);
}
static inline char msg_net_plane(struct tipc_msg *m)
{
return msg_bits(m, 5, 1, 7) + 'A';
}
static inline void msg_set_net_plane(struct tipc_msg *m, char n)
{
msg_set_bits(m, 5, 1, 7, (n - 'A'));
}
static inline u32 msg_linkprio(struct tipc_msg *m)
{
return msg_bits(m, 5, 4, 0x1f);
}
static inline void msg_set_linkprio(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 5, 4, 0x1f, n);
}
static inline u32 msg_bearer_id(struct tipc_msg *m)
{
return msg_bits(m, 5, 9, 0x7);
}
static inline void msg_set_bearer_id(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 5, 9, 0x7, n);
}
static inline u32 msg_redundant_link(struct tipc_msg *m)
{
return msg_bits(m, 5, 12, 0x1);
}
static inline void msg_set_redundant_link(struct tipc_msg *m, u32 r)
{
msg_set_bits(m, 5, 12, 0x1, r);
}
static inline char *msg_media_addr(struct tipc_msg *m)
{
return (char *)&m->hdr[TIPC_MEDIA_ADDR_OFFSET];
}
/*
* Word 9
*/
static inline u32 msg_msgcnt(struct tipc_msg *m)
{
return msg_bits(m, 9, 16, 0xffff);
}
static inline void msg_set_msgcnt(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 9, 16, 0xffff, n);
}
static inline u32 msg_bcast_tag(struct tipc_msg *m)
{
return msg_bits(m, 9, 16, 0xffff);
}
static inline void msg_set_bcast_tag(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 9, 16, 0xffff, n);
}
static inline u32 msg_max_pkt(struct tipc_msg *m)
{
return msg_bits(m, 9, 16, 0xffff) * 4;
}
static inline void msg_set_max_pkt(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 9, 16, 0xffff, (n / 4));
}
static inline u32 msg_link_tolerance(struct tipc_msg *m)
{
return msg_bits(m, 9, 0, 0xffff);
}
static inline void msg_set_link_tolerance(struct tipc_msg *m, u32 n)
{
msg_set_bits(m, 9, 0, 0xffff, n);
}
static inline u32 tipc_msg_tot_importance(struct tipc_msg *m)
{
if ((msg_user(m) == MSG_FRAGMENTER) && (msg_type(m) == FIRST_FRAGMENT))
return msg_importance(msg_get_wrapped(m));
return msg_importance(m);
}
static inline u32 msg_tot_origport(struct tipc_msg *m)
{
if ((msg_user(m) == MSG_FRAGMENTER) && (msg_type(m) == FIRST_FRAGMENT))
return msg_origport(msg_get_wrapped(m));
return msg_origport(m);
}
struct sk_buff *tipc_buf_acquire(u32 size);
bool tipc_msg_reverse(u32 own_addr, struct sk_buff *buf, u32 *dnode,
int err);
void tipc_msg_init(u32 own_addr, struct tipc_msg *m, u32 user, u32 type,
u32 hsize, u32 destnode);
struct sk_buff *tipc_msg_create(uint user, uint type, uint hdr_sz,
uint data_sz, u32 dnode, u32 onode,
u32 dport, u32 oport, int errcode);
int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf);
bool tipc_msg_bundle(struct sk_buff_head *list, struct sk_buff *skb, u32 mtu);
bool tipc_msg_make_bundle(struct sk_buff_head *list,
struct sk_buff *skb, u32 mtu, u32 dnode);
bool tipc_msg_extract(struct sk_buff *skb, struct sk_buff **iskb, int *pos);
int tipc_msg_build(struct tipc_msg *mhdr, struct msghdr *m,
int offset, int dsz, int mtu, struct sk_buff_head *list);
bool tipc_msg_lookup_dest(struct net *net, struct sk_buff *skb, u32 *dnode,
int *err);
struct sk_buff *tipc_msg_reassemble(struct sk_buff_head *list);
/* tipc_skb_peek(): peek and reserve first buffer in list
* @list: list to be peeked in
* Returns pointer to first buffer in list, if any
*/
static inline struct sk_buff *tipc_skb_peek(struct sk_buff_head *list,
spinlock_t *lock)
{
struct sk_buff *skb;
spin_lock_bh(lock);
skb = skb_peek(list);
if (skb)
skb_get(skb);
spin_unlock_bh(lock);
return skb;
}
/* tipc_skb_peek_port(): find a destination port, ignoring all destinations
* up to and including 'filter'.
* Note: ignoring previously tried destinations minimizes the risk of
* contention on the socket lock
* @list: list to be peeked in
* @filter: last destination to be ignored from search
* Returns a destination port number, of applicable.
*/
static inline u32 tipc_skb_peek_port(struct sk_buff_head *list, u32 filter)
{
struct sk_buff *skb;
u32 dport = 0;
bool ignore = true;
spin_lock_bh(&list->lock);
skb_queue_walk(list, skb) {
dport = msg_destport(buf_msg(skb));
if (!filter || skb_queue_is_last(list, skb))
break;
if (dport == filter)
ignore = false;
else if (!ignore)
break;
}
spin_unlock_bh(&list->lock);
return dport;
}
/* tipc_skb_dequeue(): unlink first buffer with dest 'dport' from list
* @list: list to be unlinked from
* @dport: selection criteria for buffer to unlink
*/
static inline struct sk_buff *tipc_skb_dequeue(struct sk_buff_head *list,
u32 dport)
{
struct sk_buff *_skb, *tmp, *skb = NULL;
spin_lock_bh(&list->lock);
skb_queue_walk_safe(list, _skb, tmp) {
if (msg_destport(buf_msg(_skb)) == dport) {
__skb_unlink(_skb, list);
skb = _skb;
break;
}
}
spin_unlock_bh(&list->lock);
return skb;
}
/* tipc_skb_queue_tail(): add buffer to tail of list;
* @list: list to be appended to
* @skb: buffer to append. Always appended
* @dport: the destination port of the buffer
* returns true if dport differs from previous destination
*/
static inline bool tipc_skb_queue_tail(struct sk_buff_head *list,
struct sk_buff *skb, u32 dport)
{
struct sk_buff *_skb = NULL;
bool rv = false;
spin_lock_bh(&list->lock);
_skb = skb_peek_tail(list);
if (!_skb || (msg_destport(buf_msg(_skb)) != dport) ||
(skb_queue_len(list) > 32))
rv = true;
__skb_queue_tail(list, skb);
spin_unlock_bh(&list->lock);
return rv;
}
#endif
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