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Implements 'next hop keep' option for BGP.

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This option allows to keep the received next hop even in cases when
the route is sent to an interface with a different subnet.
This commit is contained in:
Ondrej Zajicek 2013-04-16 17:27:34 +02:00
parent 9ff5257357
commit 48bc232f08
4 changed files with 14 additions and 3 deletions
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5
doc/bird.sgml
View File

@ -1329,6 +1329,11 @@ for each neighbor using the following configuration parameters:
circumvent misconfigurations of other routers. Default:
disabled.
<tag>next hop keep</tag> Forward the received Next Hop
attribute even in situations where the local address should be
used instead, like when the route is sent to an interface with
a different subnet. Default: disabled.
<tag>missing lladdr self|drop|ignore</tag>Next Hop attribute
in BGP-IPv6 sometimes contains just the global IPv6 address,
but sometimes it has to contain both global and link-local

8
proto/bgp/attrs.c
View File

@ -935,7 +935,8 @@ bgp_create_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *p
rta->dest != RTD_ROUTER ||
ipa_equal(rta->gw, IPA_NONE) ||
ipa_has_link_scope(rta->gw) ||
(!p->is_internal && (!p->neigh || (rta->iface != p->neigh->iface))))
(!p->is_internal && !p->cf->next_hop_keep &&
(!p->neigh || (rta->iface != p->neigh->iface))))
set_next_hop(z, p->source_addr);
else
set_next_hop(z, rta->gw);
@ -1003,10 +1004,13 @@ bgp_update_attrs(struct bgp_proto *p, rte *e, ea_list **attrs, struct linpool *p
/* iBGP -> keep next_hop, eBGP multi-hop -> use source_addr,
* eBGP single-hop -> keep next_hop if on the same iface.
* If the next_hop is zero (i.e. link-local), keep only if on the same iface.
*
* Note that same-iface-check uses iface from route, which is based on gw.
*/
a = ea_find(e->attrs->eattrs, EA_CODE(EAP_BGP, BA_NEXT_HOP));
if (a && !p->cf->next_hop_self &&
((p->is_internal && ipa_nonzero(*((ip_addr *) a->u.ptr->data))) ||
(p->cf->next_hop_keep ||
(p->is_internal && ipa_nonzero(*((ip_addr *) a->u.ptr->data))) ||
(p->neigh && (e->attrs->iface == p->neigh->iface))))
{
/* Leave the original next hop attribute, will check later where does it point */

1
proto/bgp/bgp.h
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@ -24,6 +24,7 @@ struct bgp_config {
int multihop; /* Number of hops if multihop */
int ttl_security; /* Enable TTL security [RFC5082] */
int next_hop_self; /* Always set next hop to local IP address */
int next_hop_keep; /* Do not touch next hop attribute */
int missing_lladdr; /* What we will do when we don' know link-local addr, see MLL_* */
int gw_mode; /* How we compute route gateway from next_hop attr, see GW_* */
int compare_path_lengths; /* Use path lengths when selecting best route */

3
proto/bgp/config.Y
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@ -76,7 +76,8 @@ bgp_proto:
| bgp_proto KEEPALIVE TIME expr ';' { BGP_CFG->keepalive_time = $4; }
| bgp_proto MULTIHOP ';' { BGP_CFG->multihop = 64; }
| bgp_proto MULTIHOP expr ';' { BGP_CFG->multihop = $3; if (($3<1) || ($3>255)) cf_error("Multihop must be in range 1-255"); }
| bgp_proto NEXT HOP SELF ';' { BGP_CFG->next_hop_self = 1; }
| bgp_proto NEXT HOP SELF ';' { BGP_CFG->next_hop_self = 1; BGP_CFG->next_hop_keep = 0; }
| bgp_proto NEXT HOP KEEP ';' { BGP_CFG->next_hop_keep = 1; BGP_CFG->next_hop_self = 0; }
| bgp_proto MISSING LLADDR SELF ';' { BGP_CFG->missing_lladdr = MLL_SELF; }
| bgp_proto MISSING LLADDR DROP ';' { BGP_CFG->missing_lladdr = MLL_DROP; }
| bgp_proto MISSING LLADDR IGNORE ';' { BGP_CFG->missing_lladdr = MLL_IGNORE; }