Hi, I found the traditional BGP and MP-BGP are independent in bird, if use MP_REACH_NLRI, IPV4 NLRI are not used. Has any case that need to support traditional BGP and MP-BGP at the same time ? That mean have a configuration option that create UPDATE message with MP-BGP and traditional BGP, transmit IPV4 route and IPV6 route in one UPDATE message. Thanks Arvin -----Original Message----- From: Ondrej Zajicek <santiago@crfreenet.org> Sent: Wednesday, April 11, 2018 5:26 PM To: Arvin Gan <AGan@advaoptical.com> Cc: bird-users@network.cz Subject: Re: BGP attribute ext-next-hop On Wed, Apr 11, 2018 at 07:55:28AM +0000, Arvin Gan wrote:
Hi ,
Thanks for your response. Could you help me for another question. If ext-next-hop is enabled and AFI is BGP_AF_IPV4, next- hop is a IPV4 address, when update message created, the function bgp_create_mp_reach is called, what is the format of UPDATE message ? Firstly, bgp_encode_attrs function encode all attributes, is the attribute BA_NEXT_HOP encoded in this step ?
Hi In traditional BGP (encoded by bgp_create_ip_reach() function), NEXT_HOP is encoded like other attributes by bgp_encode_next_hop() function from attrs.c file as part of bgp_encode_attrs(). In MP-BGP (encoded by bgp_create_mp_reach() function), NEXT_HOP attribute should not be encoded independently as part of bgp_encode_attrs(), but is encoded by bgp_encode_next_hop_ip() function (or its variant based on SAFI), called through dispatch function directly from bgp_create_mp_reach()). But now when i checked it, it seem like the condition in bgp_encode_next_hop() does not take in to account ext-next-hop option. So it is possible there is a bug here.
If yes, as comment said, IPV4 NLRI is not used; If no, bgp_encode_next_hop assert next-hop is 16 bytes or 32 bytes, but IPV4 next-hop is 4 bytes....
The assert in bgp_encode_next_hop_ip() function checks the length of the internal representation of the next hop, which is always 16 bytes (type ip_addr), even if IPv4 next hop is used (in such case it is encoded as IPv4-mapped IPv6 address). Function ipa_to_ip4() gets 4B ip4_addr from 16B ip_addr. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santiago@crfreenet.org) OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) "To err is human -- to blame it on a computer is even more so."