Fix AS path detection

diff --git a/src/bgp_client.rs b/src/bgp_client.rs
index 5f436b1ca106f12d132952436961cd5df0db07a7..8dfb3eba579d94cbc0c3297f1cea9a6e7fccca1a 100644 (file)
--- 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() {