From 226b696cb2f4daf899be0197d619cb5e2fe9defc Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Tue, 21 Jul 2020 15:28:17 -0400 Subject: [PATCH] Fix AS path detection --- src/bgp_client.rs | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) diff --git a/src/bgp_client.rs b/src/bgp_client.rs index 5f436b1..8dfb3eb 100644 --- a/src/bgp_client.rs +++ b/src/bgp_client.rs @@ -259,14 +259,35 @@ impl BGPClient { }); let primary_route = path_vecs.pop().unwrap(); - 'asn_candidates: for asn in primary_route.path_suffix.iter().rev() { - if *asn == 0 { continue 'asn_candidates; } - for secondary_route in path_vecs.iter() { - if !secondary_route.path_suffix.contains(asn) { - continue 'asn_candidates; + if path_vecs.len() > 3 { + // If we have at least 3 paths, try to find the last unique ASN which doesn't show up in other paths + // If we hit a T1 that is reasonably assumed to care about net neutrality, return the + // previous ASN. + let mut prev_asn = 0; + 'asn_candidates: for asn in primary_route.path_suffix.iter().rev() { + if *asn == 0 { continue 'asn_candidates; } + match *asn { + // Included: CenturyLink (L3), Cogent, Telia, NTT, GTT, Level3, + // GBLX (L3), Zayo, TI Sparkle Seabone, HE, Telefonica + // Left out from Caida top-20: TATA, PCCW, Vodafone, RETN, Orange, Telstra, + // Singtel, Rostelecom, DTAG + 209|174|1299|2914|3257|3356|3549|6461|6762|6939|12956 if prev_asn != 0 => return prev_asn, + _ => if path_vecs.iter().any(|route| !route.path_suffix.contains(asn)) { + if prev_asn != 0 { return prev_asn } else { + // Multi-origin prefix, just give up and take the last AS in the + // default path + break 'asn_candidates; + } + } else { + // We only ever possibly return an ASN if it appears in all paths + prev_asn = *asn; + }, } } - return *asn; + // All paths were the same, if the first ASN is non-0, return it. + if prev_asn != 0 { + return prev_asn; + } } for asn in primary_route.path_suffix.iter().rev() { -- 2.39.5