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BGP: Fix the setting of link-local nexthops in some situations

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This patch addresses three main issues:
a. Passing along the global IPv6 nexthop received from the EBGP peer to
IBGP peers but setting the link-local IPv6 nexthop to ourselves when
advertising EBGP-learnt routes to IBGP peers (in the absence of outbound
route-map or other overrides). The fix is to not send a link-local IPv6
nexthop in this case.

b. Passing along the link-local IPv6 nexthop received from one peer to
another peer which is (or may be) on a different subnet. This violates the
semantics of link-local IPv6 address. The fix is to set the nexthop to
ourselves in the situation where the nexthop normally has to be passed
but is a link-local IPv6 address.

c. Different behavior wrt nexthop advertisement for BGP unnumbered peering
if it is setup using link-local IPv6 address versus IPv4 /30 or /31. The
fix is to make the behavior consistent as long as the interface config is
the same in both cases.

Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>
Reviewed-by: Daniel Walton <dwalton@cumulusnetworks.com>

Ticket: CM-7846, CM-8043
Reviewed By: CCR-3749
Testing Done: Manual testing, bgpsmoke (on 2.5-br)

Note: Imported from 2.5-br patch bgpd-fix-link-local-nexthop-setting.patch
This commit is contained in:
vivek 2015-11-15 07:17:47 -08:00
parent 0e10f22cd1
commit 003c1ba05a
2 changed files with 35 additions and 10 deletions
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16
bgpd/bgp_route.c
View file

@ -1336,7 +1336,7 @@ subgroup_announce_check (struct bgp_info *ri, struct update_subgroup *subgrp,
if (peer->sort == BGP_PEER_EBGP
&& attr->flag & ATTR_FLAG_BIT (BGP_ATTR_MULTI_EXIT_DISC))
{
if (ri->peer != bgp->peer_self && ! transparent
if (from != bgp->peer_self && ! transparent
&& ! CHECK_FLAG (peer->af_flags[afi][safi], PEER_FLAG_MED_UNCHANGED))
attr->flag &= ~(ATTR_FLAG_BIT (BGP_ATTR_MULTI_EXIT_DISC));
}
@ -1360,6 +1360,7 @@ subgroup_announce_check (struct bgp_info *ri, struct update_subgroup *subgrp,
* the peer (group) is configured to receive link-local nexthop unchanged
* and it is available in the prefix OR we're not reflecting the route and
* the peer (group) to whom we're going to announce is on a shared network
* and this is either a self-originated route or the peer is EBGP.
*/
if (p->family == AF_INET6 || peer_cap_enhe(peer))
{
@ -1367,7 +1368,8 @@ subgroup_announce_check (struct bgp_info *ri, struct update_subgroup *subgrp,
if ((CHECK_FLAG (peer->af_flags[afi][safi],
PEER_FLAG_NEXTHOP_LOCAL_UNCHANGED) &&
IN6_IS_ADDR_LINKLOCAL (&attr->extra->mp_nexthop_local)) ||
(!reflect && peer->shared_network))
(!reflect && peer->shared_network &&
(from == bgp->peer_self || peer->sort == BGP_PEER_EBGP)))
{
attr->extra->mp_nexthop_len = BGP_ATTR_NHLEN_IPV6_GLOBAL_AND_LL;
}
@ -1470,6 +1472,16 @@ subgroup_announce_check (struct bgp_info *ri, struct update_subgroup *subgrp,
if (!paf)
subgroup_announce_reset_nhop ((peer_cap_enhe(peer) ? AF_INET6 : p->family), attr);
}
/* If IPv6/MP and nexthop does not have any override and happens to
* be a link-local address, reset it so that we don't pass along the
* source's link-local IPv6 address to recipients who may not be on
* the same interface.
*/
if (p->family == AF_INET6 || peer_cap_enhe(peer))
{
if (IN6_IS_ADDR_LINKLOCAL (&attr->extra->mp_nexthop_global))
subgroup_announce_reset_nhop (AF_INET6, attr);
}
}
return 1;

29
bgpd/bgp_zebra.c
View file

@ -885,11 +885,24 @@ bgp_nexthop_set (union sockunion *local, union sockunion *remote,
/* IPv6 nexthop*/
ret = if_get_ipv6_global (ifp, &nexthop->v6_global);
/* There is no global nexthop. */
if (!ret)
if_get_ipv6_local (ifp, &nexthop->v6_global);
{
/* There is no global nexthop. Use link-local address as both the
* global and link-local nexthop. In this scenario, the expectation
* for interop is that the network admin would use a route-map to
* specify the global IPv6 nexthop.
*/
if_get_ipv6_local (ifp, &nexthop->v6_global);
memcpy (&nexthop->v6_local, &nexthop->v6_global,
IPV6_MAX_BYTELEN);
}
else
if_get_ipv6_local (ifp, &nexthop->v6_local);
if (if_lookup_by_ipv4 (&remote->sin.sin_addr))
peer->shared_network = 1;
else
peer->shared_network = 0;
#endif /* HAVE_IPV6 */
}
@ -934,13 +947,13 @@ bgp_nexthop_set (union sockunion *local, union sockunion *remote,
memcpy (&nexthop->v6_local, &local->sin6.sin6_addr,
IPV6_MAX_BYTELEN);
}
}
if (IN6_IS_ADDR_LINKLOCAL (&local->sin6.sin6_addr) ||
if_lookup_by_ipv6 (&remote->sin6.sin6_addr, remote->sin6.sin6_scope_id))
peer->shared_network = 1;
else
peer->shared_network = 0;
if (IN6_IS_ADDR_LINKLOCAL (&local->sin6.sin6_addr) ||
if_lookup_by_ipv6 (&remote->sin6.sin6_addr, remote->sin6.sin6_scope_id))
peer->shared_network = 1;
else
peer->shared_network = 0;
}
/* KAME stack specific treatment. */
#ifdef KAME