another pointless yak shave: autodetect hostname

crossfire/server.rkt

@@ -865,7 +865,8 @@
                        listen-addr (config-get 'listen-port integer?)))
   (define public-addr
     (match (config-get 'public-addr (or/c 'auto string?))
-      ['auto (error "TODO auto public-addr unimplemented")]
+      ['auto (with-handlers ([exn:fail? (lambda (_) (error "failed to autodetect hostname"))])
+               (get-hostname))]
       [addr addr]))
   (define public-port
     (match (config-get 'public-port (or/c 'auto integer?))

crossfire/static-support.rkt

@@ -86,9 +86,9 @@
 ;; misc ffi calls not provided by racket (because ????)
 ;; racket should have fsync like cmon
 (module+ misc-calls
-  (require ffi/unsafe/port racket/match)
+  (require ffi/unsafe/port ffi/vector racket/list racket/match racket/string)
 
-  (provide port-fsync count-cpus current-seconds-monotonic)
+  (provide port-fsync count-cpus current-seconds-monotonic get-hostname)
 
   ;; XXX : platform-specific behavior
 
@@ -120,6 +120,24 @@
       ['unix (port-fsync/unix port)]
       [x (error "don't know how to fsync on" x)]))
 
+  (define get-hostname/unix
+    (let ([gethostname-call #f])
+      (lambda ()
+        (when (false? gethostname-call)
+          (set! gethostname-call
+            (get-ffi-obj/runtime "gethostname" (get-libc/init)
+              (_fun #:save-errno 'posix (name : (_bytes o 256)) (size : _int = 256)
+                    -> (res : _int)
+                    -> (if (zero? res)
+                         (cast name _bytes _string/utf-8)
+                         (raise (exn:fail (format "gethostname: errno ~a" (saved-errno))
+                                          (current-continuation-marks))))))))
+        (gethostname-call))))
+
+  (define (get-hostname)
+    (match (system-type 'os)
+      ['unix (get-hostname/unix)]
+      [x (error "don't know how to get-hostname on" x)]))
 
   ;; this provides an actual count of the number of CPUs on the system, even without
   ;; --enable-futures by hooking into the underlying rktio call that gets skipped when the current

etc/crossfire.rktd

@@ -5,7 +5,7 @@
  (listen-addr "0.0.0.0")
  (listen-port 25446)
  ;; the "public" ip (or domain name) and port of this node
- ;; - auto for addr selects the first interface addr (linux only)
+ ;; - auto for addr uses /etc/hostname, if present (linux only)
  ;; - auto for port uses the same as listen-port
- (public-addr "127.0.0.1")
+ (public-addr auto)
  (public-port auto))