Commit 48bc232f authored by Ondřej Zajíček's avatar Ondřej Zajíček

Implements 'next hop keep' option for BGP.

This option allows to keep the received next hop even in cases when
the route is sent to an interface with a different subnet.
parent 9ff52573
......@@ -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
......
......@@ -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 */
......
......@@ -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 */
......
......@@ -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; }
......
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