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BGP: Send hold timer 

Implement BGP Send hold timer according to draft-ietf-idr-bgp-sendholdtimer.
The Send hold timer drops the session if the neighbor is sending keepalives,
but does not receive our messages, causing the TCP connection to stall.
This commit is contained in:
Katerina Kubecova 2023-10-27 17:11:06 +02:00 committed by Ondrej Zajicek
parent 3fb06fea1d
commit bcf2327425
5 changed files with 76 additions and 4 deletions
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17
doc/bird.sgml
View File

@ -3157,6 +3157,23 @@ using the following configuration parameters:
negotiation. If the proposed hold time would lead to a lower value of
the keepalive time, the session is rejected with error. Default: none.
<tag><label id="bgp-send-hold-time">send hold time <m/number/</tag>
Maximum time in seconds betweeen successfull transmissions of BGP messages.
Send hold timer drops the session if the neighbor is sending keepalives,
but does not receive our messages, causing the TCP connection to stall.
This may happen due to malfunctioning or overwhelmed neighbor. See
<HTMLURL URL="https://datatracker.ietf.org/doc/draft-ietf-idr-bgp-sendholdtimer/"
name="draft-ietf-idr-bgp-sendholdtimer"> for more details.
Like the option <cf/keepalive time/, the effective value depends on the
negotiated hold time, as it is scaled to maintain proportion between the
send hold time and the keepalive time. If it is set to zero, the timer
is disabled. Default: double of the hold timer limit.
The option <cf/disable rx/ is intended only for testing this feature and
should not be used anywhere else. It discards received messages and
disables the hold timer.
<tag><label id="bgp-connect-delay-time">connect delay time <m/number/</tag>
Delay in seconds between protocol startup and the first attempt to
connect. Default: 5 seconds.

35
proto/bgp/bgp.c
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@ -375,6 +375,8 @@ bgp_close_conn(struct bgp_conn *conn)
conn->keepalive_timer = NULL;
rfree(conn->hold_timer);
conn->hold_timer = NULL;
rfree(conn->send_hold_timer);
conn->send_hold_timer = NULL;
rfree(conn->tx_ev);
conn->tx_ev = NULL;
rfree(conn->sk);
@ -673,6 +675,13 @@ bgp_conn_enter_established_state(struct bgp_conn *conn)
p->channel_map[c->index] = c;
}
/* Breaking rx_hook for simulating receive problem */
if (p->cf->disable_rx)
{
conn->sk->rx_hook = NULL;
tm_stop(conn->hold_timer);
}
/* proto_notify_state() will likely call bgp_feed_begin(), setting c->feed_state */
bgp_conn_set_state(conn, BS_ESTABLISHED);
@ -1044,6 +1053,27 @@ bgp_keepalive_timeout(timer *t)
ev_run(conn->tx_ev);
}
void
bgp_send_hold_timeout(timer *t)
{
struct bgp_conn *conn = t->data;
struct bgp_proto *p = conn->bgp;
if (conn->state == BS_CLOSE)
return;
/* Error codes not yet assigned by IANA */
uint code = 4;
uint subcode = 1;
/* Like bgp_error() but without NOTIFICATION */
bgp_log_error(p, BE_BGP_TX, "Error", code, subcode, NULL, 0);
bgp_store_error(p, conn, BE_BGP_TX, (code << 16) | subcode);
bgp_conn_enter_idle_state(conn);
bgp_update_startup_delay(p);
bgp_stop(p, 0, NULL, 0);
}
static void
bgp_setup_conn(struct bgp_proto *p, struct bgp_conn *conn)
{
@ -1058,6 +1088,7 @@ bgp_setup_conn(struct bgp_proto *p, struct bgp_conn *conn)
conn->connect_timer = tm_new_init(p->p.pool, bgp_connect_timeout, conn, 0, 0);
conn->hold_timer = tm_new_init(p->p.pool, bgp_hold_timeout, conn, 0, 0);
conn->keepalive_timer = tm_new_init(p->p.pool, bgp_keepalive_timeout, conn, 0, 0);
conn->send_hold_timer = tm_new_init(p->p.pool, bgp_send_hold_timeout, conn, 0, 0);
conn->tx_ev = ev_new_init(p->p.pool, bgp_kick_tx, conn);
}
@ -2619,7 +2650,9 @@ bgp_show_proto_info(struct proto *P)
tm_remains(p->conn->hold_timer), p->conn->hold_time);
cli_msg(-1006, " Keepalive timer: %t/%u",
tm_remains(p->conn->keepalive_timer), p->conn->keepalive_time);
}
cli_msg(-1006, " Send hold timer: %t/%u",
tm_remains(p->conn->send_hold_timer), p->conn->send_hold_time);
}
#if 0
struct bgp_stats *s = &p->stats;

6
proto/bgp/bgp.h
View File

@ -117,6 +117,8 @@ struct bgp_config {
int setkey; /* Set MD5 password to system SA/SP database */
u8 local_role; /* Set peering role with neighbor [RFC 9234] */
int require_roles; /* Require configured roles on both sides */
int send_hold_time;
int disable_rx; /* Stop reading messages after handshake (for simulating error) */
/* Times below are in seconds */
unsigned gr_time; /* Graceful restart timeout */
unsigned llgr_time; /* Long-lived graceful restart stale time */
@ -307,6 +309,7 @@ struct bgp_conn {
timer *connect_timer;
timer *hold_timer;
timer *keepalive_timer;
timer *send_hold_timer;
event *tx_ev;
u32 packets_to_send; /* Bitmap of packet types to be sent */
u32 channels_to_send; /* Bitmap of channels with packets to be sent */
@ -315,7 +318,7 @@ struct bgp_conn {
int notify_code, notify_subcode, notify_size;
byte *notify_data;
uint hold_time, keepalive_time; /* Times calculated from my and neighbor's requirements */
uint hold_time, keepalive_time, send_hold_time; /* Times calculated from my and neighbor's requirements */
};
struct bgp_proto {
@ -558,6 +561,7 @@ void bgp_conn_enter_openconfirm_state(struct bgp_conn *conn);
void bgp_conn_enter_established_state(struct bgp_conn *conn);
void bgp_conn_enter_close_state(struct bgp_conn *conn);
void bgp_conn_enter_idle_state(struct bgp_conn *conn);
void broke_bgp_listening(struct channel *C);
void bgp_handle_graceful_restart(struct bgp_proto *p);
void bgp_graceful_restart_done(struct bgp_channel *c);
void bgp_refresh_begin(struct bgp_channel *c);

5
proto/bgp/config.Y
View File

@ -32,7 +32,7 @@ CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY, KEEPALIVE,
LIVED, STALE, IMPORT, IBGP, EBGP, MANDATORY, INTERNAL, EXTERNAL, SETS,
DYNAMIC, RANGE, NAME, DIGITS, BGP_AIGP, AIGP, ORIGINATE, COST, ENFORCE,
FIRST, FREE, VALIDATE, BASE, ROLE, ROLES, PEER, PROVIDER, CUSTOMER,
RS_SERVER, RS_CLIENT, REQUIRE, BGP_OTC, GLOBAL)
RS_SERVER, RS_CLIENT, REQUIRE, BGP_OTC, GLOBAL, SEND)
%type <i> bgp_nh
%type <i32> bgp_afi
@ -77,6 +77,7 @@ bgp_proto_start: proto_start BGP {
BGP_CFG->local_role = BGP_ROLE_UNDEFINED;
BGP_CFG->dynamic_name = "dynbgp";
BGP_CFG->check_link = -1;
BGP_CFG->send_hold_time = -1;
}
;
@ -182,6 +183,7 @@ bgp_proto:
| bgp_proto CONNECT RETRY TIME expr ';' { BGP_CFG->connect_retry_time = $5; }
| bgp_proto KEEPALIVE TIME expr ';' { BGP_CFG->keepalive_time = $4; if (($4<1) || ($4>65535)) cf_error("Keepalive time must be in range 1-65535"); }
| bgp_proto MIN KEEPALIVE TIME expr ';' { BGP_CFG->min_keepalive_time = $5; }
| bgp_proto SEND HOLD TIME expr';' { BGP_CFG->send_hold_time = $5; }
| bgp_proto ERROR FORGET TIME expr ';' { BGP_CFG->error_amnesia_time = $5; }
| bgp_proto ERROR WAIT TIME expr ',' expr ';' { BGP_CFG->error_delay_time_min = $5; BGP_CFG->error_delay_time_max = $7; }
| bgp_proto DISABLE AFTER ERROR bool ';' { BGP_CFG->disable_after_error = $5; }
@ -222,6 +224,7 @@ bgp_proto:
| bgp_proto ENFORCE FIRST AS bool ';' { BGP_CFG->enforce_first_as = $5; }
| bgp_proto LOCAL ROLE bgp_role_name ';' { BGP_CFG->local_role = $4; }
| bgp_proto REQUIRE ROLES bool ';' { BGP_CFG->require_roles = $4; }
| bgp_proto DISABLE RX bool ';' { BGP_CFG->disable_rx = $4; }
;
bgp_afi:

17
proto/bgp/packets.c
View File

@ -926,6 +926,10 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, uint len)
(p->cf->keepalive_time * hold_time / p->cf->hold_time) :
hold_time / 3;
uint send_hold_time = (p->cf->send_hold_time >= 0) ?
(p->cf->send_hold_time * hold_time / p->cf->hold_time) :
2 * hold_time;
/* Keepalive time might be rounded down to zero */
if (hold_time && !keepalive_time)
keepalive_time = 1;
@ -1034,6 +1038,7 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, uint len)
/* Update our local variables */
conn->hold_time = hold_time;
conn->keepalive_time = keepalive_time;
conn->send_hold_time = send_hold_time;
conn->as4_session = conn->local_caps->as4_support && caps->as4_support;
conn->ext_messages = conn->local_caps->ext_messages && caps->ext_messages;
p->remote_id = id;
@ -1043,6 +1048,7 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, uint len)
bgp_schedule_packet(conn, NULL, PKT_KEEPALIVE);
bgp_start_timer(conn->hold_timer, conn->hold_time);
bgp_start_timer(conn->send_hold_timer, conn->send_hold_time);
bgp_conn_enter_openconfirm_state(conn);
}
@ -3060,7 +3066,11 @@ bgp_send(struct bgp_conn *conn, uint type, uint len)
put_u16(buf+16, len);
buf[18] = type;
return sk_send(sk, len);
int success = sk_send(sk, len);
if (success && ((conn->state == BS_ESTABLISHED) || (conn->state == BS_OPENCONFIRM)))
bgp_start_timer(conn->send_hold_timer, conn->send_hold_time);
return success;
}
/**
@ -3220,6 +3230,10 @@ bgp_tx(sock *sk)
{
struct bgp_conn *conn = sk->data;
/* Pending message was passed to kernel */
if ((conn->state == BS_ESTABLISHED) || (conn->state == BS_OPENCONFIRM))
bgp_start_timer(conn->send_hold_timer, conn->send_hold_time);
DBG("BGP: TX hook\n");
uint max = 1024;
while (--max && (bgp_fire_tx(conn) > 0))
@ -3261,6 +3275,7 @@ static struct {
{ 3, 10, "Invalid network field" },
{ 3, 11, "Malformed AS_PATH" },
{ 4, 0, "Hold timer expired" },
{ 4, 1, "Send hold timer expired" }, /* Provisional [draft-ietf-idr-bgp-sendholdtimer] */
{ 5, 0, "Finite state machine error" }, /* Subcodes are according to [RFC6608] */
{ 5, 1, "Unexpected message in OpenSent state" },
{ 5, 2, "Unexpected message in OpenConfirm state" },