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Filter: Add 'weight' route attribute

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Add 'weight' route attribute that allows to get and set ECMP weight of
nexthops. Similar to 'gw' attribute, it is limited to the first nexthop,
but it is useful for handling BGP multipath, where an ECMP route is
merged from multiple regular routes.
This commit is contained in:
Ondrej Zajicek (work) 2020-12-02 05:02:26 +01:00
parent 2465867712
commit 8cc5bb09e3
4 changed files with 27 additions and 1 deletions
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9
doc/bird.sgml
View file

@ -1674,6 +1674,15 @@ Common route attributes are:
creation/removal. Zero is returned for routes with undefined outgoing
interfaces. Read-only.
<tag><label id="rta-weight"><m/int/ weight</tag>
Multipath weight of route next hops. Valid values are 1-256. Reading
returns the weight of the first next hop, setting it sets weights of all
next hops to the specified value. Therefore, this attribute is not much
useful for manipulating individual next hops of an ECMP route, but can
be used in BGP multipath setup to set weights of individual routes that
are merged to one ECMP route during export to the Kernel protocol
(with active <ref id="krt-merge-paths" name="marge paths"> option).
<tag><label id="rta-igp-metric"><m/int/ igp_metric</tag>
The optional attribute that can be used to specify a distance to the
network for routes that do not have a native protocol metric attribute

3
filter/config.Y
View file

@ -278,7 +278,7 @@ CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
SET, STRING, BGPMASK, BGPPATH, CLIST, ECLIST, LCLIST,
IF, THEN, ELSE, CASE,
TRUE, FALSE, RT, RO, UNKNOWN, GENERIC,
FROM, GW, NET, MASK, PROTO, SOURCE, SCOPE, DEST, IFNAME, IFINDEX,
FROM, GW, NET, MASK, PROTO, SOURCE, SCOPE, DEST, IFNAME, IFINDEX, WEIGHT,
PREFERENCE,
ROA_CHECK, ASN, SRC, DST,
IS_V4, IS_V6,
@ -750,6 +750,7 @@ static_attr:
| DEST { $$ = f_new_static_attr(T_ENUM_RTD, SA_DEST, 0); }
| IFNAME { $$ = f_new_static_attr(T_STRING, SA_IFNAME, 0); }
| IFINDEX { $$ = f_new_static_attr(T_INT, SA_IFINDEX, 1); }
| WEIGHT { $$ = f_new_static_attr(T_INT, SA_WEIGHT, 0); }
;
term:

1
filter/data.h
View file

@ -99,6 +99,7 @@ enum f_sa_code {
SA_DEST,
SA_IFNAME,
SA_IFINDEX,
SA_WEIGHT,
} PACKED;
/* Static attribute definition (members of struct rta) */

15
filter/f-inst.c
View file

@ -516,6 +516,7 @@
case SA_DEST: RESULT(sa.f_type, i, rta->dest); break;
case SA_IFNAME: RESULT(sa.f_type, s, rta->nh.iface ? rta->nh.iface->name : ""); break;
case SA_IFINDEX: RESULT(sa.f_type, i, rta->nh.iface ? rta->nh.iface->index : 0); break;
case SA_WEIGHT: RESULT(sa.f_type, i, rta->nh.weight + 1); break;
default:
bug("Invalid static attribute access (%u/%u)", sa.f_type, sa.sa_code);
@ -586,6 +587,20 @@
}
break;
case SA_WEIGHT:
{
int i = v1.val.i;
if (i < 1 || i > 256)
runtime( "Setting weight value out of bounds" );
if (rta->dest != RTD_UNICAST)
runtime( "Setting weight needs regular nexthop " );
/* Set weight on all next hops */
for (struct nexthop *nh = &rta->nh; nh; nh = nh->next)
nh->weight = i - 1;
}
break;
default:
bug("Invalid static attribute access (%u/%u)", sa.f_type, sa.sa_code);
}