From 90275458edca6ee2d385e4eba2380d6f477a2a77 Mon Sep 17 00:00:00 2001
From: Milo <iitalics@gmail.com>
Date: Fri, 31 Jan 2020 22:35:34 -0500
Subject: [PATCH] router registration and lookup

---
 router | 89 ++++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 56 insertions(+), 33 deletions(-)

diff --git a/router b/router
index 3491bca..f49accd 100755
--- a/router
+++ b/router
@@ -5,7 +5,9 @@
 (require json
          "iputil.rkt"
          "unix-socket.rkt"
-         "msg.rkt")
+         "msg.rkt"
+         "radix-tree.rkt"
+         )
 
 ;; info : Peer
 ;; sock-in : Input-Port
@@ -14,24 +16,41 @@
   [info sock-in sock-out]
   #:transparent)
 
-;; alist : [Listof [Cons IP Route]]
-(struct router
-  [(alist #:mutable)]
-  #:transparent)
+;; a Router is a [RTof [Listof [Cons Peer Route]]]
 
 ;; -> Router
 (define (make-router)
-  (router '()))
+  (make-rt))
 
-;; Router Route IP -> Void
-(define (router-add! rs r src)
-  (set-router-alist! rs
-                     (cons (cons src r)
-                           (router-alist rs))))
+;; Router Route Peer -> Void
+(define (router-add! rt r peer)
+  (rt-update! rt
+              (subnet->bl (route-subnet r))
+              (lambda (rst) (cons (cons peer r) rst))
+              (lambda () '())))
 
-;; Router IP -> (U IP #f)
-(define (router-find-best rs src)
-  #f)
+(define (route< r1 r2)
+  #|
+      (route< r1 r2) iff "r1 wins"
+
+      1. The path with the highest "localpref" wins. If the "localpref"s are equal...
+      2. The path with "selfOrigin" = true wins. If all selfOrigins are the equal...
+      3. The path with the shortest "ASPath" wins. If multiple routes have the shortest length...
+      4. The path with the best "origin" wins, were IGP > EGP > UNK.
+         If multiple routes have the best origin...
+      5. The path from the neighbor router with the lowest IP address.
+  |#
+  #t)
+
+;; Router IP -> (U Peer #f)
+(define (router-find-best rt src-ip)
+  (match (sort (rt-lookup rt
+                        (ip->bl src-ip)
+                        (λ () '()))
+             route<
+             #:key cdr)
+    [(list* (cons peer _) _) peer]
+    [_ #f]))
 
 ;; Str [Listof Peer-Conn] -> Void
 ;; --
@@ -52,42 +71,46 @@
                   (channel-put mail (list peer msg))
                   (loop))))))
 
-  (define (ip->peer-conn ip)
-    (findf (λ (p)
-             (equal? ip (peer-ip (peer-conn-info p))))
+  (define (ip->peer ip)
+    (findf (λ (peer)
+             (equal? ip (peer-ip peer)))
+           (map peer-conn-info peer-conns)))
+
+  (define (peer->peer-conn peer)
+    (findf (λ (pc)
+             (equal? peer (peer-conn-info pc)))
            peer-conns))
 
   (define router
     (make-router))
 
-  (define (loop)
-    (match-define (list src-peer msg) (channel-get mail))
-    (printf "====\nfrom ~a:\n~s\n" src-peer msg)
+  (let loop ()
+    (match-define (list src-peer-conn msg) (channel-get mail))
+    (printf "====\nfrom ~a:\n~s\n" src-peer-conn msg)
     (match msg
 
       [(msg:update src dst r)
-       (router-add! router r src)]
+       (router-add! router
+                    r
+                    (ip->peer src))
+       (rt-dump router)]
 
       [(msg:data src dst data)
-       (define-values [dst-peer resp-msg]
+       (define-values [dst-peer-conn resp-msg]
          (match (router-find-best router dst)
            [#f
-            (values peer
-                    (msg:no-route src
-                                  dst))]
-           [dst-peer-ip
-            (values (ip->peer-conn dst-peer-ip)
+            (values src-peer-conn
+                    (msg:no-route src dst))]
+           [dst-peer
+            (values (peer->peer-conn dst-peer)
                     msg)]))
-       (printf "----\nwant to send back ~a to ~a\n"
-               dst-peer
+       (printf "----\nwant to send back to ~a:\n~a\n"
+               (peer-conn-info dst-peer-conn)
                resp-msg)]
 
       [_
        (printf "----\nignored\n")])
-    (loop))
-
-  (printf "waiting for messages...\n")
-  (loop))
+    (loop)))
 
 ;; Str [Listof Peer] ->
 ;; Router main