multicast?

multicast?

[Greg Troxel]

I'm writing a program with guile (1.6.5) and guile-gnome.
I have created a socket, bound it to a port and connected it to a
mcast destination address and port.  Sending works fine.  Looking in
libguile/socket.c, I can't find support for joining multicast groups.
This is via setsockopt with struct mreq.

I don't see anything in HEAD either.

Has anyone written this?

-- 
        Greg Troxel <gdt@ir.bbn.com>


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Re: multicast? [patch]

[Greg Troxel]

  I have created a socket, bound it to a port and connected it to a
  mcast destination address and port.  Sending works fine.  Looking in
  libguile/socket.c, I can't find support for joining multicast groups.
  This is via setsockopt with struct mreq.

--- libguile/socket.c.orig	2004-08-26 22:16:38.000000000 -0400
+++ libguile/socket.c
@@ -563,12 +563,18 @@ SCM_DEFINE (scm_setsockopt, "setsockopt"
 {
   int fd;
   int optlen = -1;
+
   /* size of optval is the largest supported option.  */
+  union bigopt {
+    size_t a;
 #ifdef HAVE_STRUCT_LINGER
-  char optval[sizeof (struct linger)];
-#else
-  char optval[sizeof (size_t)];
+    struct linger l;
 #endif
+    struct ip_mreq m;
+  };
+  /* XXX: why not just use the union? */
+  char optval[sizeof (union bigopt) + 20];
+
   int ilevel, ioptname;
 
   sock = SCM_COERCE_OUTPORT (sock);
@@ -630,6 +636,21 @@ SCM_DEFINE (scm_setsockopt, "setsockopt"
 	    (*(size_t *) optval) = (size_t) lv;
 	  }
     }
+
+  if (ilevel == IPPROTO_IP &&
+      (ioptname == IP_ADD_MEMBERSHIP || ioptname == IP_DROP_MEMBERSHIP))
+    {
+      struct ip_mreq mreq;
+
+      /* Fourth argument must be a pair of addresses. */
+      SCM_ASSERT (SCM_CONSP (value), value, SCM_ARG4, FUNC_NAME);
+      mreq.imr_multiaddr.s_addr = htonl(SCM_NUM2ULONG (4, SCM_CAR (value)));
+      mreq.imr_interface.s_addr = htonl(SCM_NUM2ULONG (4, SCM_CDR (value)));
+
+      memcpy(optval, &mreq, sizeof(mreq));
+      optlen = sizeof(mreq);
+    }
+
   if (optlen == -1)
     {
       /* Most options take an int.  */
@@ -1393,6 +1414,11 @@ scm_init_socket ()
   scm_c_define ("MSG_DONTROUTE", SCM_MAKINUM (MSG_DONTROUTE));
 #endif
 
+#ifdef IP_ADD_MEMBERSHIP
+  scm_c_define ("IP_ADD_MEMBERSHIP", SCM_MAKINUM (IP_ADD_MEMBERSHIP));
+  scm_c_define ("IP_DROP_MEMBERSHIP", SCM_MAKINUM (IP_DROP_MEMBERSHIP));
+#endif
+
   scm_add_feature ("socket");
 
 #include "libguile/socket.x"

-- 
        Greg Troxel <gdt@ir.bbn.com>


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Re: multicast? [patch]

[Marius Vollmer]

Greg Troxel <gdt@ir.bbn.com> writes:

> [a nice patch]

I'm not completely sure what to do with this.  Adding more multicast
functinoality is certainly very good and needs to happen.

On the other hand, can we hope to ever cover all socket options that
are out there?  Maybe we should have different functions for different
kinds of socket options, or maybe not.

Opinions?

I will install your patch anyway, but I'm afraid we need the
papers... more about this in private mail.


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Re: multicast? [patch]

[Greg Troxel]

  I'm not completely sure what to do with this.  Adding more multicast
  functinoality is certainly very good and needs to happen.

This is really all that's needed - joining groups and setting TTL.
As a scripting language, guile should support all the normal network
operations.
I don't find making setsockopt fancier a bad thing.
It would be cool to have a table of commands and types, but then it's
more like g-wrap.


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        Greg Troxel <gdt@ir.bbn.com>


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Re: multicast? [patch]

[Marius Vollmer]

Marius Vollmer <marius.vollmer@uni-dortmund.de> writes:

> I will install your patch anyway, [...]

Ok, it is in HEAD now.

2005-02-28  Marius Vollmer  <mvo@zagadka.de>

	* socket.c (scm_setsockopt): Handle IP_ADD_MEMBERSHIP and
	IP_DROP_MEMBERSHIP options.  Also, reorganized the code a bit for
	cleanliness.
	(scm_init_socket): Define IP_ADD_MEMBERSHIP and
	IP_DROP_MEMBERSHIP.
	Thanks to Greg Troxel!


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