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BGP: Improve custom BGP attributes

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- Implement EA_GET for custom BGP attributes
 - Forbid EA_SET on existing opaque attributes
 - Forbid redefining existing attributes
 - Document possible compatibility problems
This commit is contained in:
Ondrej Zajicek 2023-10-05 21:29:04 +02:00
parent ba01a6f2e6
commit 57aa077227
5 changed files with 32 additions and 9 deletions
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12
doc/bird.sgml
View File

@ -3561,10 +3561,14 @@ some of them (marked with `<tt/O/') are optional.
name="local role"> is configured it set automatically.
</descrip>
<p>For attributes unknown by BIRD, the user can assign a name (on top level)
to an attribute by its number. This defined name can be used then to both set
(by a bytestring literal, transitive) or unset the given attribute even though
BIRD knows nothing about it:
<p>For attributes unknown by BIRD, the user can assign a name (on top level) to
an attribute by its number. This defined name can be used then to get, set (as a
bytestring, transitive) or unset the given attribute even though BIRD knows
nothing about it.
<p>Note that it is not possible to define an attribute with the same number
as one known by BIRD, therefore use of this statement carries a risk of
incompatibility with future BIRD versions.
<tt><label id="bgp-attribute-custom">attribute bgp <m/number/ bytestring <m/name/;</tt>

9
filter/f-inst.c
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@ -838,7 +838,10 @@
RESULT_(T_QUAD, i, e->u.data);
break;
case EAF_TYPE_OPAQUE:
if (da.f_type == T_ENUM_EMPTY)
RESULT_(T_ENUM_EMPTY, i, 0);
else
RESULT_(T_BYTESTRING, ad, e->u.ptr);
break;
case EAF_TYPE_IP_ADDRESS:
RESULT_(T_IP, ip, *((ip_addr *) e->u.ptr->data));
@ -870,6 +873,12 @@
ARG_ANY(1);
DYNAMIC_ATTR;
ARG_TYPE(1, da.f_type);
FID_NEW_BODY;
if (da.f_type == T_ENUM_EMPTY)
cf_error("Setting opaque attribute is not allowed");
FID_INTERPRET_BODY;
{
struct ea_list *l = lp_alloc(fs->pool, sizeof(struct ea_list) + sizeof(eattr));

6
proto/bgp/attrs.c
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@ -1152,6 +1152,12 @@ bgp_attr_known(uint code)
return (code < ARRAY_SIZE(bgp_attr_table)) && bgp_attr_table[code].name;
}
const char *
bgp_attr_name(uint code)
{
return (code < ARRAY_SIZE(bgp_attr_table)) ? bgp_attr_table[code].name : NULL;
}
void bgp_fix_attr_flags(ea_list *attrs)
{
for (u8 i = 0; i < attrs->count; i++)

1
proto/bgp/bgp.h
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@ -611,6 +611,7 @@ bgp_unset_attr(ea_list **to, struct linpool *pool, uint code)
int bgp_encode_mp_reach_mrt(struct bgp_write_state *s, eattr *a, byte *buf, uint size);
const char * bgp_attr_name(uint code);
int bgp_encode_attrs(struct bgp_write_state *s, ea_list *attrs, byte *buf, byte *end);
ea_list * bgp_decode_attrs(struct bgp_parse_state *s, byte *data, uint len);
void bgp_finish_attrs(struct bgp_parse_state *s, rta *a);

11
proto/bgp/config.Y
View File

@ -365,11 +365,14 @@ dynamic_attr: BGP_LARGE_COMMUNITY
dynamic_attr: BGP_OTC
{ $$ = f_new_dynamic_attr(EAF_TYPE_INT, T_INT, EA_CODE(PROTOCOL_BGP, BA_ONLY_TO_CUSTOMER)); } ;
custom_attr: ATTRIBUTE BGP NUM type symbol ';' {
if($3 > 255 || $3 < 1)
cf_error("Invalid attribute number. (Given %i, must be 1-255.)", $3);
if($4 != T_BYTESTRING)
custom_attr: ATTRIBUTE BGP expr type symbol ';' {
if ($3 > 255 || $3 < 1)
cf_error("Invalid attribute number (Given %i, must be 1-255)", $3);
if ($4 != T_BYTESTRING)
cf_error("Attribute type must be bytestring, not %s", f_type_name($4));
if (bgp_attr_name($3))
cf_error("Attribute BGP.%d already known as %s", $3, bgp_attr_name($3));
struct f_dynamic_attr *a = cfg_alloc(sizeof(struct f_dynamic_attr));
*a = f_new_dynamic_attr(f_type_attr($4), T_BYTESTRING, EA_CODE(PROTOCOL_BGP, $3));
a->flags = BAF_TRANSITIVE | BAF_OPTIONAL;