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tipc: simplify link mtu negotiation
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When a link is being established, the two endpoints advertise their
respective interface MTU in the transmitted RESET and ACTIVATE messages.
If there is any difference, the lower of the two MTUs will be selected
for use by both endpoints.

However, as a remnant of earlier attempts to introduce TIPC level
routing. there also exists an MTU discovery mechanism. If an intermediate
node has a lower MTU than the two endpoints, they will discover this
through a bisectional approach, and finally adopt this MTU for common use.

Since there is no TIPC level routing, and probably never will be,
this mechanism doesn't make any sense, and only serves to make the
link level protocol unecessarily complex.

In this commit, we eliminate the MTU discovery algorithm,and fall back
to the simple MTU advertising approach. This change is fully backwards
compatible.

Reviewed-by: Ying Xue <[email protected]>
Signed-off-by: Jon Maloy <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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@davem330
Jon Paul Maloy authored and davem330 committed Apr 2, 2015
1 parent dff29b1 commit ed193ec
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Showing 4 changed files with 43 additions and 111 deletions.
4 changes: 2 additions & 2 deletions net/tipc/bcast.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -413,7 +413,7 @@ static void bclink_accept_pkt(struct tipc_node *node, u32 seqno)
*/
if (((seqno - tn->own_addr) % TIPC_MIN_LINK_WIN) == 0) {
tipc_link_proto_xmit(node->active_links[node->addr & 1],
STATE_MSG, 0, 0, 0, 0, 0);
STATE_MSG, 0, 0, 0, 0);
tn->bcl->stats.sent_acks++;
}
}
Expand Down Expand Up @@ -899,7 +899,7 @@ int tipc_bclink_init(struct net *net)
skb_queue_head_init(&bclink->inputq);
bcl->owner = &bclink->node;
bcl->owner->net = net;
bcl->max_pkt = MAX_PKT_DEFAULT_MCAST;
bcl->mtu = MAX_PKT_DEFAULT_MCAST;
tipc_link_set_queue_limits(bcl, BCLINK_WIN_DEFAULT);
bcl->bearer_id = MAX_BEARERS;
rcu_assign_pointer(tn->bearer_list[MAX_BEARERS], &bcbearer->bearer);
Expand Down
129 changes: 32 additions & 97 deletions net/tipc/link.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -136,34 +136,6 @@ static struct tipc_link *tipc_parallel_link(struct tipc_link *l)
return l->owner->active_links[1];
}

static void link_init_max_pkt(struct tipc_link *l_ptr)
{
struct tipc_node *node = l_ptr->owner;
struct tipc_net *tn = net_generic(node->net, tipc_net_id);
struct tipc_bearer *b_ptr;
u32 max_pkt;

rcu_read_lock();
b_ptr = rcu_dereference_rtnl(tn->bearer_list[l_ptr->bearer_id]);
if (!b_ptr) {
rcu_read_unlock();
return;
}
max_pkt = (b_ptr->mtu & ~3);
rcu_read_unlock();

if (max_pkt > MAX_MSG_SIZE)
max_pkt = MAX_MSG_SIZE;

l_ptr->max_pkt_target = max_pkt;
if (l_ptr->max_pkt_target < MAX_PKT_DEFAULT)
l_ptr->max_pkt = l_ptr->max_pkt_target;
else
l_ptr->max_pkt = MAX_PKT_DEFAULT;

l_ptr->max_pkt_probes = 0;
}

/*
* Simple non-static link routines (i.e. referenced outside this file)
*/
Expand Down Expand Up @@ -304,7 +276,8 @@ struct tipc_link *tipc_link_create(struct tipc_node *n_ptr,
msg_set_bearer_id(msg, b_ptr->identity);
strcpy((char *)msg_data(msg), if_name);
l_ptr->net_plane = b_ptr->net_plane;
link_init_max_pkt(l_ptr);
l_ptr->advertised_mtu = b_ptr->mtu;
l_ptr->mtu = l_ptr->advertised_mtu;
l_ptr->priority = b_ptr->priority;
tipc_link_set_queue_limits(l_ptr, b_ptr->window);
l_ptr->next_out_no = 1;
Expand Down Expand Up @@ -465,8 +438,8 @@ void tipc_link_reset(struct tipc_link *l_ptr)
/* Link is down, accept any session */
l_ptr->peer_session = INVALID_SESSION;

/* Prepare for max packet size negotiation */
link_init_max_pkt(l_ptr);
/* Prepare for renewed mtu size negotiation */
l_ptr->mtu = l_ptr->advertised_mtu;

l_ptr->state = RESET_UNKNOWN;

Expand Down Expand Up @@ -563,19 +536,15 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->checkpoint = l_ptr->next_in_no;
if (tipc_bclink_acks_missing(l_ptr->owner)) {
tipc_link_proto_xmit(l_ptr, STATE_MSG,
0, 0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
} else if (l_ptr->max_pkt < l_ptr->max_pkt_target) {
tipc_link_proto_xmit(l_ptr, STATE_MSG,
1, 0, 0, 0, 0);
0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
}
link_set_timer(l_ptr, cont_intv);
break;
}
l_ptr->state = WORKING_UNKNOWN;
l_ptr->fsm_msg_cnt = 0;
tipc_link_proto_xmit(l_ptr, STATE_MSG, 1, 0, 0, 0, 0);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 1, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv / 4);
break;
Expand All @@ -586,7 +555,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->state = RESET_RESET;
l_ptr->fsm_msg_cnt = 0;
tipc_link_proto_xmit(l_ptr, ACTIVATE_MSG,
0, 0, 0, 0, 0);
0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv);
break;
Expand All @@ -609,7 +578,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->state = RESET_RESET;
l_ptr->fsm_msg_cnt = 0;
tipc_link_proto_xmit(l_ptr, ACTIVATE_MSG,
0, 0, 0, 0, 0);
0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv);
break;
Expand All @@ -620,13 +589,13 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->checkpoint = l_ptr->next_in_no;
if (tipc_bclink_acks_missing(l_ptr->owner)) {
tipc_link_proto_xmit(l_ptr, STATE_MSG,
0, 0, 0, 0, 0);
0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
}
link_set_timer(l_ptr, cont_intv);
} else if (l_ptr->fsm_msg_cnt < l_ptr->abort_limit) {
tipc_link_proto_xmit(l_ptr, STATE_MSG,
1, 0, 0, 0, 0);
1, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv / 4);
} else { /* Link has failed */
Expand All @@ -636,7 +605,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->state = RESET_UNKNOWN;
l_ptr->fsm_msg_cnt = 0;
tipc_link_proto_xmit(l_ptr, RESET_MSG,
0, 0, 0, 0, 0);
0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv);
}
Expand All @@ -656,7 +625,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->state = WORKING_WORKING;
l_ptr->fsm_msg_cnt = 0;
link_activate(l_ptr);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 1, 0, 0, 0, 0);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 1, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
if (l_ptr->owner->working_links == 1)
tipc_link_sync_xmit(l_ptr);
Expand All @@ -666,7 +635,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->state = RESET_RESET;
l_ptr->fsm_msg_cnt = 0;
tipc_link_proto_xmit(l_ptr, ACTIVATE_MSG,
1, 0, 0, 0, 0);
1, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv);
break;
Expand All @@ -676,7 +645,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
link_set_timer(l_ptr, cont_intv);
break;
case TIMEOUT_EVT:
tipc_link_proto_xmit(l_ptr, RESET_MSG, 0, 0, 0, 0, 0);
tipc_link_proto_xmit(l_ptr, RESET_MSG, 0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv);
break;
Expand All @@ -694,7 +663,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
l_ptr->state = WORKING_WORKING;
l_ptr->fsm_msg_cnt = 0;
link_activate(l_ptr);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 1, 0, 0, 0, 0);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 1, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
if (l_ptr->owner->working_links == 1)
tipc_link_sync_xmit(l_ptr);
Expand All @@ -704,7 +673,7 @@ static void link_state_event(struct tipc_link *l_ptr, unsigned int event)
break;
case TIMEOUT_EVT:
tipc_link_proto_xmit(l_ptr, ACTIVATE_MSG,
0, 0, 0, 0, 0);
0, 0, 0, 0);
l_ptr->fsm_msg_cnt++;
link_set_timer(l_ptr, cont_intv);
break;
Expand Down Expand Up @@ -733,7 +702,7 @@ int __tipc_link_xmit(struct net *net, struct tipc_link *link,
struct tipc_msg *msg = buf_msg(skb_peek(list));
unsigned int maxwin = link->window;
unsigned int imp = msg_importance(msg);
uint mtu = link->max_pkt;
uint mtu = link->mtu;
uint ack = mod(link->next_in_no - 1);
uint seqno = link->next_out_no;
uint bc_last_in = link->owner->bclink.last_in;
Expand Down Expand Up @@ -1187,7 +1156,7 @@ void tipc_rcv(struct net *net, struct sk_buff *skb, struct tipc_bearer *b_ptr)
link_retrieve_defq(l_ptr, &head);
if (unlikely(++l_ptr->rcv_unacked >= TIPC_MIN_LINK_WIN)) {
l_ptr->stats.sent_acks++;
tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, 0, 0, 0);
}
tipc_link_input(l_ptr, skb);
skb = NULL;
Expand Down Expand Up @@ -1362,7 +1331,7 @@ static void link_handle_out_of_seq_msg(struct tipc_link *l_ptr,
if (tipc_link_defer_pkt(&l_ptr->deferdq, buf)) {
l_ptr->stats.deferred_recv++;
if ((skb_queue_len(&l_ptr->deferdq) % TIPC_MIN_LINK_WIN) == 1)
tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, 0, 0, 0);
} else {
l_ptr->stats.duplicates++;
}
Expand All @@ -1372,7 +1341,7 @@ static void link_handle_out_of_seq_msg(struct tipc_link *l_ptr,
* Send protocol message to the other endpoint.
*/
void tipc_link_proto_xmit(struct tipc_link *l_ptr, u32 msg_typ, int probe_msg,
u32 gap, u32 tolerance, u32 priority, u32 ack_mtu)
u32 gap, u32 tolerance, u32 priority)
{
struct sk_buff *buf = NULL;
struct tipc_msg *msg = l_ptr->pmsg;
Expand Down Expand Up @@ -1410,26 +1379,11 @@ void tipc_link_proto_xmit(struct tipc_link *l_ptr, u32 msg_typ, int probe_msg,
l_ptr->stats.sent_nacks++;
msg_set_link_tolerance(msg, tolerance);
msg_set_linkprio(msg, priority);
msg_set_max_pkt(msg, ack_mtu);
msg_set_max_pkt(msg, l_ptr->mtu);
msg_set_ack(msg, mod(l_ptr->next_in_no - 1));
msg_set_probe(msg, probe_msg != 0);
if (probe_msg) {
u32 mtu = l_ptr->max_pkt;

if ((mtu < l_ptr->max_pkt_target) &&
link_working_working(l_ptr) &&
l_ptr->fsm_msg_cnt) {
msg_size = (mtu + (l_ptr->max_pkt_target - mtu)/2 + 2) & ~3;
if (l_ptr->max_pkt_probes == 10) {
l_ptr->max_pkt_target = (msg_size - 4);
l_ptr->max_pkt_probes = 0;
msg_size = (mtu + (l_ptr->max_pkt_target - mtu)/2 + 2) & ~3;
}
l_ptr->max_pkt_probes++;
}

if (probe_msg)
l_ptr->stats.sent_probes++;
}
l_ptr->stats.sent_states++;
} else { /* RESET_MSG or ACTIVATE_MSG */
msg_set_ack(msg, mod(l_ptr->failover_checkpt - 1));
Expand All @@ -1438,7 +1392,7 @@ void tipc_link_proto_xmit(struct tipc_link *l_ptr, u32 msg_typ, int probe_msg,
msg_set_probe(msg, 0);
msg_set_link_tolerance(msg, l_ptr->tolerance);
msg_set_linkprio(msg, l_ptr->priority);
msg_set_max_pkt(msg, l_ptr->max_pkt_target);
msg_set_max_pkt(msg, l_ptr->advertised_mtu);
}

r_flag = (l_ptr->owner->working_links > tipc_link_is_up(l_ptr));
Expand Down Expand Up @@ -1469,8 +1423,6 @@ static void tipc_link_proto_rcv(struct tipc_link *l_ptr,
struct sk_buff *buf)
{
u32 rec_gap = 0;
u32 max_pkt_info;
u32 max_pkt_ack;
u32 msg_tol;
struct tipc_msg *msg = buf_msg(buf);

Expand Down Expand Up @@ -1513,15 +1465,8 @@ static void tipc_link_proto_rcv(struct tipc_link *l_ptr,
if (msg_linkprio(msg) > l_ptr->priority)
l_ptr->priority = msg_linkprio(msg);

max_pkt_info = msg_max_pkt(msg);
if (max_pkt_info) {
if (max_pkt_info < l_ptr->max_pkt_target)
l_ptr->max_pkt_target = max_pkt_info;
if (l_ptr->max_pkt > l_ptr->max_pkt_target)
l_ptr->max_pkt = l_ptr->max_pkt_target;
} else {
l_ptr->max_pkt = l_ptr->max_pkt_target;
}
if (l_ptr->mtu > msg_max_pkt(msg))
l_ptr->mtu = msg_max_pkt(msg);

/* Synchronize broadcast link info, if not done previously */
if (!tipc_node_is_up(l_ptr->owner)) {
Expand Down Expand Up @@ -1566,27 +1511,17 @@ static void tipc_link_proto_rcv(struct tipc_link *l_ptr,
mod(l_ptr->next_in_no));
}

max_pkt_ack = msg_max_pkt(msg);
if (max_pkt_ack > l_ptr->max_pkt) {
l_ptr->max_pkt = max_pkt_ack;
l_ptr->max_pkt_probes = 0;
}

max_pkt_ack = 0;
if (msg_probe(msg)) {
if (msg_probe(msg))
l_ptr->stats.recv_probes++;
if (msg_size(msg) > sizeof(l_ptr->proto_msg))
max_pkt_ack = msg_size(msg);
}

/* Protocol message before retransmits, reduce loss risk */
if (l_ptr->owner->bclink.recv_permitted)
tipc_bclink_update_link_state(l_ptr->owner,
msg_last_bcast(msg));

if (rec_gap || (msg_probe(msg))) {
tipc_link_proto_xmit(l_ptr, STATE_MSG, 0, rec_gap, 0,
0, max_pkt_ack);
tipc_link_proto_xmit(l_ptr, STATE_MSG, 0,
rec_gap, 0, 0);
}
if (msg_seq_gap(msg)) {
l_ptr->stats.recv_nacks++;
Expand Down Expand Up @@ -1816,7 +1751,7 @@ static void link_set_supervision_props(struct tipc_link *l_ptr, u32 tol)

void tipc_link_set_queue_limits(struct tipc_link *l, u32 win)
{
int max_bulk = TIPC_MAX_PUBLICATIONS / (l->max_pkt / ITEM_SIZE);
int max_bulk = TIPC_MAX_PUBLICATIONS / (l->mtu / ITEM_SIZE);

l->window = win;
l->backlog[TIPC_LOW_IMPORTANCE].limit = win / 2;
Expand Down Expand Up @@ -1988,14 +1923,14 @@ int tipc_nl_link_set(struct sk_buff *skb, struct genl_info *info)

tol = nla_get_u32(props[TIPC_NLA_PROP_TOL]);
link_set_supervision_props(link, tol);
tipc_link_proto_xmit(link, STATE_MSG, 0, 0, tol, 0, 0);
tipc_link_proto_xmit(link, STATE_MSG, 0, 0, tol, 0);
}
if (props[TIPC_NLA_PROP_PRIO]) {
u32 prio;

prio = nla_get_u32(props[TIPC_NLA_PROP_PRIO]);
link->priority = prio;
tipc_link_proto_xmit(link, STATE_MSG, 0, 0, 0, prio, 0);
tipc_link_proto_xmit(link, STATE_MSG, 0, 0, 0, prio);
}
if (props[TIPC_NLA_PROP_WIN]) {
u32 win;
Expand Down Expand Up @@ -2100,7 +2035,7 @@ static int __tipc_nl_add_link(struct net *net, struct tipc_nl_msg *msg,
if (nla_put_u32(msg->skb, TIPC_NLA_LINK_DEST,
tipc_cluster_mask(tn->own_addr)))
goto attr_msg_full;
if (nla_put_u32(msg->skb, TIPC_NLA_LINK_MTU, link->max_pkt))
if (nla_put_u32(msg->skb, TIPC_NLA_LINK_MTU, link->mtu))
goto attr_msg_full;
if (nla_put_u32(msg->skb, TIPC_NLA_LINK_RX, link->next_in_no))
goto attr_msg_full;
Expand Down
12 changes: 5 additions & 7 deletions net/tipc/link.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -123,9 +123,8 @@ struct tipc_stats {
* @backlog_limit: backlog queue congestion thresholds (indexed by importance)
* @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)
* @mtu: current maximum packet size for this link
* @advertised_mtu: advertised own mtu when link is being established
* @transmitq: queue for sent, non-acked messages
* @backlogq: queue for messages waiting to be sent
* @next_out_no: next sequence number to use for outbound messages
Expand Down Expand Up @@ -176,9 +175,8 @@ struct tipc_link {
struct sk_buff *failover_skb;

/* Max packet negotiation */
u32 max_pkt;
u32 max_pkt_target;
u32 max_pkt_probes;
u16 mtu;
u16 advertised_mtu;

/* Sending */
struct sk_buff_head transmq;
Expand Down Expand Up @@ -233,7 +231,7 @@ int tipc_link_xmit(struct net *net, struct sk_buff_head *list, u32 dest,
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);
u32 gap, u32 tolerance, u32 priority);
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);
Expand Down
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