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Revert "bgpd: Handle Addpath capability using dynamic capabilities"
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This reverts commit 05cf9d0.

TL;DR; Handling BGP AddPath capability is not trivial (possible) dynamically.

When the sender is AddPath-capable and sends NLRIs encoded with AddPath ID,
and at the same time the receiver sends AddPath capability "disable-addpath-rx"
(flag update) via dynamic capabilities, both peers are out of sync about the
AddPath state. The receiver thinks already he's not AddPath-capable anymore,
hence it tries to parse NLRIs as non-AddPath, while they are actually encoded
as AddPath.

AddPath capability itself does not provide (in RFC) any mechanism on backward
compatible way to handle NLRIs if they come mixed (AddPath + non-AddPath).

This explains why we have failures in our CI periodically.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>
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@ton31337
ton31337 committed Jan 28, 2025
1 parent 273dc49 commit 3110597
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Showing 7 changed files with 56 additions and 401 deletions.
33 changes: 1 addition & 32 deletions bgpd/bgp_addpath.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,6 @@

#include "bgp_addpath.h"
#include "bgp_route.h"
#include "bgp_open.h"
#include "bgp_packet.h"

static const struct bgp_addpath_strategy_names strat_names[BGP_ADDPATH_MAX] = {
{
Expand Down Expand Up @@ -361,31 +359,6 @@ void bgp_addpath_type_changed(struct bgp *bgp)
}
}

int bgp_addpath_capability_action(enum bgp_addpath_strat addpath_type,
uint8_t paths)
{
int action = CAPABILITY_ACTION_UNSET;

switch (addpath_type) {
case BGP_ADDPATH_ALL:
case BGP_ADDPATH_BEST_PER_AS:
action = CAPABILITY_ACTION_SET;
break;
case BGP_ADDPATH_BEST_SELECTED:
if (paths)
action = CAPABILITY_ACTION_SET;
else
action = CAPABILITY_ACTION_UNSET;
break;
case BGP_ADDPATH_NONE:
case BGP_ADDPATH_MAX:
action = CAPABILITY_ACTION_UNSET;
break;
}

return action;
}

/*
* Change the addpath type assigned to a peer, or peer group. In addition to
* adjusting the counts, peer sessions will be reset as needed to make the
Expand All @@ -400,7 +373,6 @@ void bgp_addpath_set_peer_type(struct peer *peer, afi_t afi, safi_t safi,
struct listnode *node, *nnode;
struct peer *tmp_peer;
struct peer_group *group;
int action = bgp_addpath_capability_action(addpath_type, paths);

if (safi == SAFI_LABELED_UNICAST)
safi = SAFI_UNICAST;
Expand Down Expand Up @@ -458,12 +430,9 @@ void bgp_addpath_set_peer_type(struct peer *peer, afi_t afi, safi_t safi,
}
}
} else {
if (!CHECK_FLAG(peer->cap, PEER_CAP_DYNAMIC_RCV) &&
!CHECK_FLAG(peer->cap, PEER_CAP_DYNAMIC_ADV))
peer_change_action(peer, afi, safi, peer_change_reset);
peer_change_action(peer, afi, safi, peer_change_reset);
}

bgp_capability_send(peer, afi, safi, CAPABILITY_CODE_ADDPATH, action);
}

/*
Expand Down
10 changes: 1 addition & 9 deletions bgpd/bgp_addpath.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,20 +15,14 @@
#include "bgpd/bgp_table.h"
#include "lib/json.h"

struct bgp_addpath_capability {
uint16_t afi;
uint8_t safi;
uint8_t flags;
};
#define BGP_ADDPATH_TX_ID_FOR_DEFAULT_ORIGINATE 1

struct bgp_paths_limit_capability {
uint16_t afi;
uint8_t safi;
uint16_t paths_limit;
} __attribute__((packed));

#define BGP_ADDPATH_TX_ID_FOR_DEFAULT_ORIGINATE 1

void bgp_addpath_init_bgp_data(struct bgp_addpath_bgp_data *d);

bool bgp_addpath_is_addpath_used(struct bgp_addpath_bgp_data *d, afi_t afi,
Expand Down Expand Up @@ -69,6 +63,4 @@ void bgp_addpath_update_ids(struct bgp *bgp, struct bgp_dest *dest, afi_t afi,
safi_t safi);

void bgp_addpath_type_changed(struct bgp *bgp);
extern int bgp_addpath_capability_action(enum bgp_addpath_strat addpath_type,
uint8_t paths);
#endif
189 changes: 2 additions & 187 deletions bgpd/bgp_packet.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1207,7 +1207,6 @@ void bgp_capability_send(struct peer *peer, afi_t afi, safi_t safi,
uint16_t len;
uint32_t gr_restart_time;
uint8_t addpath_afi_safi_count = 0;
bool adv_addpath_tx = false;
unsigned long number_of_orfs_p;
uint8_t number_of_orfs = 0;
const char *capability = lookup_msg(capcode_str, capability_code,
Expand Down Expand Up @@ -1372,87 +1371,6 @@ void bgp_capability_send(struct peer *peer, afi_t afi, safi_t safi,
COND_FLAG(peer->cap, PEER_CAP_LLGR_ADV,
action == CAPABILITY_ACTION_SET);
break;
case CAPABILITY_CODE_ADDPATH:
FOREACH_AFI_SAFI (afi, safi) {
if (peer->afc[afi][safi]) {
addpath_afi_safi_count++;

/* Only advertise addpath TX if a feature that
* will use it is
* configured */
if (peer->addpath_type[afi][safi] !=
BGP_ADDPATH_NONE)
adv_addpath_tx = true;

/* If we have enabled labeled unicast, we MUST check
* against unicast SAFI because addpath IDs are
* allocated under unicast SAFI, the same as the RIB
* is managed in unicast SAFI.
*/
if (safi == SAFI_LABELED_UNICAST)
if (peer->addpath_type[afi][SAFI_UNICAST] !=
BGP_ADDPATH_NONE)
adv_addpath_tx = true;
}
}

stream_putc(s, action);
stream_putc(s, CAPABILITY_CODE_ADDPATH);
stream_putc(s, CAPABILITY_CODE_ADDPATH_LEN *
addpath_afi_safi_count);

FOREACH_AFI_SAFI (afi, safi) {
if (peer->afc[afi][safi]) {
bool adv_addpath_rx =
!CHECK_FLAG(peer->af_flags[afi][safi],
PEER_FLAG_DISABLE_ADDPATH_RX);
uint8_t flags = 0;

/* Convert AFI, SAFI to values for packet. */
bgp_map_afi_safi_int2iana(afi, safi, &pkt_afi,
&pkt_safi);

stream_putw(s, pkt_afi);
stream_putc(s, pkt_safi);

if (adv_addpath_rx) {
SET_FLAG(flags, BGP_ADDPATH_RX);
SET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_RX_ADV);
} else {
UNSET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_RX_ADV);
}

if (adv_addpath_tx) {
SET_FLAG(flags, BGP_ADDPATH_TX);
SET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_TX_ADV);
if (safi == SAFI_LABELED_UNICAST)
SET_FLAG(peer->af_cap[afi]
[SAFI_UNICAST],
PEER_CAP_ADDPATH_AF_TX_ADV);
} else {
UNSET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_TX_ADV);
}

stream_putc(s, flags);
}
}

if (bgp_debug_neighbor_events(peer))
zlog_debug("%pBP sending CAPABILITY has %s %s for afi/safi: %s/%s",
peer,
action == CAPABILITY_ACTION_SET
? "Advertising"
: "Removing",
capability, iana_afi2str(pkt_afi),
iana_safi2str(pkt_safi));

COND_FLAG(peer->cap, PEER_CAP_ADDPATH_ADV,
action == CAPABILITY_ACTION_SET);
break;
case CAPABILITY_CODE_PATHS_LIMIT:
FOREACH_AFI_SAFI (afi, safi) {
if (!peer->afc[afi][safi])
Expand Down Expand Up @@ -1608,6 +1526,7 @@ void bgp_capability_send(struct peer *peer, afi_t afi, safi_t safi,
case CAPABILITY_CODE_REFRESH:
case CAPABILITY_CODE_AS4:
case CAPABILITY_CODE_DYNAMIC:
case CAPABILITY_CODE_ADDPATH:
case CAPABILITY_CODE_ENHANCED_RR:
case CAPABILITY_CODE_ENHE:
case CAPABILITY_CODE_EXT_MESSAGE:
Expand Down Expand Up @@ -3100,108 +3019,6 @@ static int bgp_route_refresh_receive(struct peer_connection *connection,
return BGP_PACKET_NOOP;
}

static void bgp_dynamic_capability_addpath(uint8_t *pnt, int action,
struct capability_header *hdr,
struct peer *peer)
{
uint8_t *data = pnt + 3;
uint8_t *end = data + hdr->length;
size_t len = end - data;
afi_t afi;
safi_t safi;

if (action == CAPABILITY_ACTION_SET) {
if (len % CAPABILITY_CODE_ADDPATH_LEN) {
flog_warn(EC_BGP_CAPABILITY_INVALID_LENGTH,
"Add Path: Received invalid length %zu, non-multiple of 4",
len);
return;
}

SET_FLAG(peer->cap, PEER_CAP_ADDPATH_RCV);

while (data + CAPABILITY_CODE_ADDPATH_LEN <= end) {
afi_t afi;
safi_t safi;
iana_afi_t pkt_afi;
iana_safi_t pkt_safi;
struct bgp_addpath_capability bac;

memcpy(&bac, data, sizeof(bac));
pkt_afi = ntohs(bac.afi);
pkt_safi = safi_int2iana(bac.safi);

/* If any other value (other than 1-3) is received,
* then the capability SHOULD be treated as not
* understood and ignored.
*/
if (!bac.flags || bac.flags > 3) {
flog_warn(EC_BGP_CAPABILITY_INVALID_LENGTH,
"Add Path: Received invalid send/receive value %u in Add Path capability",
bac.flags);
goto ignore;
}

if (bgp_debug_neighbor_events(peer))
zlog_debug("%s OPEN has %s capability for afi/safi: %s/%s%s%s",
peer->host,
lookup_msg(capcode_str, hdr->code,
NULL),
iana_afi2str(pkt_afi),
iana_safi2str(pkt_safi),
(bac.flags & BGP_ADDPATH_RX)
? ", receive"
: "",
(bac.flags & BGP_ADDPATH_TX)
? ", transmit"
: "");

if (bgp_map_afi_safi_iana2int(pkt_afi, pkt_safi, &afi,
&safi)) {
if (bgp_debug_neighbor_events(peer))
zlog_debug("%s Addr-family %s/%s(afi/safi) not supported. Ignore the Addpath Attribute for this AFI/SAFI",
peer->host,
iana_afi2str(pkt_afi),
iana_safi2str(pkt_safi));
goto ignore;
} else if (!peer->afc[afi][safi]) {
if (bgp_debug_neighbor_events(peer))
zlog_debug("%s Addr-family %s/%s(afi/safi) not enabled. Ignore the AddPath capability for this AFI/SAFI",
peer->host,
iana_afi2str(pkt_afi),
iana_safi2str(pkt_safi));
goto ignore;
}

if (CHECK_FLAG(bac.flags, BGP_ADDPATH_RX))
SET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_RX_RCV);
else
UNSET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_RX_RCV);

if (CHECK_FLAG(bac.flags, BGP_ADDPATH_TX))
SET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_TX_RCV);
else
UNSET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_TX_RCV);

ignore:
data += CAPABILITY_CODE_ADDPATH_LEN;
}
} else {
FOREACH_AFI_SAFI (afi, safi) {
UNSET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_RX_RCV);
UNSET_FLAG(peer->af_cap[afi][safi],
PEER_CAP_ADDPATH_AF_TX_RCV);
}

UNSET_FLAG(peer->cap, PEER_CAP_ADDPATH_RCV);
}
}

static void bgp_dynamic_capability_paths_limit(uint8_t *pnt, int action,
struct capability_header *hdr,
struct peer *peer)
Expand Down Expand Up @@ -3887,9 +3704,6 @@ static int bgp_capability_msg_parse(struct peer *peer, uint8_t *pnt,
case CAPABILITY_CODE_LLGR:
bgp_dynamic_capability_llgr(pnt, action, hdr, peer);
break;
case CAPABILITY_CODE_ADDPATH:
bgp_dynamic_capability_addpath(pnt, action, hdr, peer);
break;
case CAPABILITY_CODE_PATHS_LIMIT:
bgp_dynamic_capability_paths_limit(pnt, action, hdr,
peer);
Expand All @@ -3903,6 +3717,7 @@ static int bgp_capability_msg_parse(struct peer *peer, uint8_t *pnt,
case CAPABILITY_CODE_REFRESH:
case CAPABILITY_CODE_AS4:
case CAPABILITY_CODE_DYNAMIC:
case CAPABILITY_CODE_ADDPATH:
case CAPABILITY_CODE_ENHANCED_RR:
case CAPABILITY_CODE_ENHE:
case CAPABILITY_CODE_EXT_MESSAGE:
Expand Down
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