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bgpd: fix Prefix-SID parsing failure case

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Prefix-SID path attribute Label-index TLV (type-1) is
used by SR-MPLS. And Label-index TLV MUST ignored
if that path attribute is append on non-Labeled-unicast
UPDATE message described on [ref1].
There is a problem case exist arround this implementation.
This commit fix that.

Before this commit,
unfortunally, setting Label-Index value is skipped at somecases.
because, Label-Index TLV implementation check the AFI/SAFI pair.
by mp_update variable that is set by bgp_mp_reach_parse function.
if MP_REACH_NLRI is present after PREFIX_SID, bgp_attr_psid_sub
function can't understand AFI/SAFI pair. and the order of each
path attributes is never no-deterministic thing for receiver.[ref2]

In this commit,
I re-located checking code of AFI/SAFI pair after path-attr loop.

[ref1](https://tools.ietf.org/html/draft-ietf-idr-bgp-prefix-sid-27#section-3.2)
> The Originator SRGB TLV may only appear in a BGP Prefix-SID attribute
> attached to IPv4/IPv6 Labeled Unicast prefixes ([RFC8277]).  It MUST
> be ignored when received for other BGP AFI/SAFI combinations.

[ref2](https://tools.ietf.org/html/rfc4271#section-5)
> The sender of an UPDATE message SHOULD order path attributes within
> the UPDATE message in ascending order of attribute type.  The
> receiver of an UPDATE message MUST be prepared to handle path
> attributes within UPDATE messages that are out of order.

Signed-off-by: Hiroki Shirokura <slank.dev@gmail.com>
This commit is contained in:
Hiroki Shirokura 2020-02-04 00:11:29 +00:00
parent 38774fc5e6
commit e5d4cda0a7
1 changed files with 11 additions and 9 deletions
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20
bgpd/bgp_attr.c
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@ -2382,15 +2382,6 @@ static bgp_attr_parse_ret_t bgp_attr_psid_sub(uint8_t type, uint16_t length,
/* Store label index; subsequently, we'll check on /* Store label index; subsequently, we'll check on
* address-family */ * address-family */
attr->label_index = label_index; attr->label_index = label_index;
/*
* Ignore the Label index attribute unless received for
* labeled-unicast
* SAFI.
*/
if (!mp_update->length
|| mp_update->safi != SAFI_LABELED_UNICAST)
attr->label_index = BGP_INVALID_LABEL_INDEX;
} }
/* Placeholder code for the IPv6 SID type */ /* Placeholder code for the IPv6 SID type */
@ -3078,6 +3069,17 @@ bgp_attr_parse_ret_t bgp_attr_parse(struct peer *peer, struct attr *attr,
} }
} }
/*
* draft-ietf-idr-bgp-prefix-sid-27#section-3:
* About Prefix-SID path attribute,
* Label-Index TLV(type1) and The Originator SRGB TLV(type-3)
* may only appear in a BGP Prefix-SID attribute attached to
* IPv4/IPv6 Labeled Unicast prefixes ([RFC8277]).
* It MUST be ignored when received for other BGP AFI/SAFI combinations.
*/
if (!attr->mp_nexthop_len || mp_update->safi != SAFI_LABELED_UNICAST)
attr->label_index = BGP_INVALID_LABEL_INDEX;
/* Check final read pointer is same as end pointer. */ /* Check final read pointer is same as end pointer. */
if (BGP_INPUT_PNT(peer) != endp) { if (BGP_INPUT_PNT(peer) != endp) {
flog_warn(EC_BGP_ATTRIBUTES_MISMATCH, flog_warn(EC_BGP_ATTRIBUTES_MISMATCH,