From b2cae3951f390ebd0e75cf5a7c668b4f90eb81ce Mon Sep 17 00:00:00 2001
From: Peter Bex <peter@more-magic.net>
Date: Mon, 6 May 2013 22:09:08 +0200
Subject: Implement buffer-length option, and export the interface
 setting/getting procedures as well as the procedure to retrieve the buffer
 length. Switch to c-pointer and use LOCATION to get pointers from scheme
 objects.

---
 bpf-interface.scm | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/bpf-interface.scm b/bpf-interface.scm
index 49046b0..5a3be0c 100644
--- a/bpf-interface.scm
+++ b/bpf-interface.scm
@@ -4,7 +4,7 @@
 ;;; Copyright (c) 2013 by Peter Bex, see file COPYING.BSD
 ;;;
 (module bpf-interface
-  (bpf-open bpf-close bpf? bpf-interface-set! bpf-interface)
+  (bpf-open bpf-close bpf? bpf-buffer-length bpf-interface bpf-interface-set!)
 
 (import chicken scheme foreign)
 
@@ -31,7 +31,7 @@
 
 (define ioctl1
   (foreign-lambda* int (((c-pointer int) err) (int fd)
-                        (unsigned-long req) (scheme-pointer val1))
+                        (unsigned-long req) (c-pointer val1))
     "int res = ioctl(fd, req, val1);"
     "*err = errno;"
     "return(res);"))
@@ -77,6 +77,9 @@
                        (e (exn i/o file) (lp (fx+ i 1) fn e))))
                  (bpf (make-bpf fd)))
             (set-finalizer! bpf bpf-close)
+            ;; Length _must_ be set before interface is assigned
+            (when buffer-length
+              (bpf-buffer-length-set! bpf buffer-length))
             (bpf-interface-set! bpf interface)
             bpf)))))
 
@@ -86,6 +89,15 @@
     (bpf-fd-set! bpf #f))
   (void))
 
+;; Returns the *actual* size that was set, the requested size is too big
+;; Remember, this can only be done *before* setting the interface.
+;; Oddly enough, the interface can be switched afterwards, so there's
+;; no way to set a new interface *and* buffer-length...
+(define (bpf-buffer-length-set! bpf requested-length)
+  (let-location ((new-length int requested-length))
+    (ioctl (bpf-fd bpf) (foreign-value "BIOCSBLEN" int) (location new-length))
+    new-length))
+
 (define interface-name-maximum-length (foreign-value "IF_NAMESIZE" int))
 
 (define (bpf-interface-set! bpf interface)
@@ -99,13 +111,18 @@
        "char *ifname = ((struct ifreq *)i)->ifr_name;"
        "strncpy(ifname, s, len);"
        "ifname[len] = '\\0';") ifreq interface len)
-    (ioctl (bpf-fd bpf) (foreign-value "BIOCSETIF" int) ifreq)
+    (ioctl (bpf-fd bpf) (foreign-value "BIOCSETIF" int) (location ifreq))
     (void)))
 
 (define (bpf-interface bpf)
   (let ((ifreq (make-blob (foreign-value "sizeof(struct ifreq)" int))))
-    (ioctl (bpf-fd bpf) (foreign-value "BIOCGETIF" int) ifreq)
+    (ioctl (bpf-fd bpf) (foreign-value "BIOCGETIF" int) (location ifreq))
     ((foreign-lambda* c-string ((scheme-pointer i))
        "C_return(((struct ifreq *)i)->ifr_name);") ifreq)))
 
+(define (bpf-buffer-length bpf)
+  (let-location ((length int))
+    (ioctl (bpf-fd bpf) (foreign-value "BIOCGBLEN" int) (location length))
+    length))
+
 )
-- 
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