Hi , Thanks for so quick reply. Do you mean if (s->channel->afi == BGP_AF_IPV4) maybe have bug, need change to if (s->channel->afi == BGP_AF_IPV4 && !s->channel-> ext_next_hop) ?
Thanks Arvin -----Original Message----- From: Ondrej Zajicek <santi...@crfreenet.org> Sent: Wednesday, April 11, 2018 5:26 PM To: Arvin Gan <a...@advaoptical.com> Cc: email@example.com 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: santi...@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."