On 18.10.2013 15:23, Milan Kocian wrote:

Sometimes its useful feature. So make it optional per bgp protocol. Based on hint http://permalink.gmane.org/gmane.network.bird.user/944

Signed-off-by: Milan Kocian <milon@wq.cz> --- proto/bgp/attrs.c | 5 +++-- proto/bgp/bgp.h | 1 + proto/bgp/config.Y | 4 +++- 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/proto/bgp/attrs.c b/proto/bgp/attrs.c index c27a498..27a2694 100644 --- a/proto/bgp/attrs.c +++ b/proto/bgp/attrs.c @@ -1704,8 +1704,9 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin bgp_remove_as4_attrs(bgp, a);

/* If the AS path attribute contains our AS, reject the routes */ - if (bgp_as_path_loopy(bgp, a)) - goto withdraw; + if (!bgp->cf->allow_as_in) + if (bgp_as_path_loopy(bgp, a)) + goto withdraw; Removing loop check at all is wrong (as it can lead to real loops). Typical implementation include configurable maximum number of local ASn that can be contained in path.

/* Two checks for IBGP loops caused by route reflection, RFC 4456 */ if (bgp_originator_id_loopy(bgp, a) || diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h index 77a3671..f45c3aa 100644 --- a/proto/bgp/bgp.h +++ b/proto/bgp/bgp.h @@ -44,6 +44,7 @@ struct bgp_config { int passive; /* Do not initiate outgoing connection */ int interpret_communities; /* Hardwired handling of well-known communities */ int secondary; /* Accept also non-best routes (i.e. RA_ACCEPTED) */ + int allow_as_in; unsigned connect_retry_time; unsigned hold_time, initial_hold_time; unsigned keepalive_time; diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y index d5e5aac..709f5dc 100644 --- a/proto/bgp/config.Y +++ b/proto/bgp/config.Y @@ -26,7 +26,7 @@ CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY, PREFER, OLDER, MISSING, LLADDR, DROP, IGNORE, ROUTE, REFRESH, INTERPRET, COMMUNITIES, BGP_ORIGINATOR_ID, BGP_CLUSTER_LIST, IGP, TABLE, GATEWAY, DIRECT, RECURSIVE, MED, TTL, SECURITY, DETERMINISTIC, - SECONDARY) + SECONDARY, ALLOW, ALLOW_AS_IN)

CF_GRAMMAR

@@ -49,6 +49,7 @@ bgp_proto_start: proto_start BGP { BGP_CFG->advertise_ipv4 = 1; BGP_CFG->interpret_communities = 1; BGP_CFG->default_local_pref = 100; + BGP_CFG->allow_as_in = 0; } ;

@@ -78,6 +79,7 @@ bgp_proto: | 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_CFG->next_hop_keep = 0; } | bgp_proto NEXT HOP KEEP ';' { BGP_CFG->next_hop_keep = 1; BGP_CFG->next_hop_self = 0; } + | bgp_proto ALLOW AS IN ';' { BGP_CFG->allow_as_in = 1; } | 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; }