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| sam at inf.enst.fr |
 Posted: Wed Dec 08, 1999 5:51 pm |
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Guest
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I decided to play with multicast sockets in Erlang, and discovered 3
problems with the following code:
-module (tm).
-export ([test/0]).
-include_lib ("kernel/src/inet_int.hrl").
-define (MULTIADDR, {224, 225, 224, 225}).
-define (MULTIPORT, 1501).
ip4_reverse ({A, B, C, D}) -> {D, C, B, A}.
test () ->
{ok, S} = inet_udp:open (?MULTIPORT, [{reuseadddr, 1},
{multicast_ttl, 16},
{multicast_loop, true},
{add_membership, {ip4_reverse (?MULTIADDR),
{0, 0, 0, 0}}}]),
inet_udp:send (S, ?MULTIADDR, ?MULTIPORT, "toto"),
receive
X ->
io:format ("~p~n", [X])
end,
inet_udp:close (S).
The three problems are:
(1) If an option is given an invalid name, or if it has a bad
argument, it is silently ignored. Try changing reuseaddr into
reuseaddddr, it should succeed. *WISHLIST*
(2) One needs to use {0, 0, 0, 0} to mean INADDR_ANY. Maybe ip_any/1
could be exported from inet.erl so that it can be used easily.
*WISHLIST*
(3) On my Intel Linux box, I need to reverse the multicast group
address given to setsockopt (..., ADD_MEMBERSHIP, ...). On my
Sparc box, I must NOT use this address reversing. There is some
suspicious code in inet_drv.c that may concern this:
L_set_mreq:
mreq_val.imr_multiaddr.s_addr = ival;
mreq_val.imr_interface.s_addr = get_int32(ptr);
I just wrote the following patch, but may not have the time to
have it tested tonight (I have no Erlang semi-compiled here). If
someone volunteers to test it, she will be welcome  Otherwise,
I'll give the answer tomorrow.
--- erts/emulator/drivers/common/inet_drv.c.orig Wed Dec 8 18:46:00 1999
+++ erts/emulator/drivers/common/inet_drv.c Wed Dec 8 18:47:22 1999
_at__at_ -1514,8 +1514,8 _at__at_
type = IP_DROP_MEMBERSHIP;
DEBUGF(("Descriptor %d: [IPPROTO_IP] IP_DROP_MEMBERSHIP(%d)
",desc->s,ival));
L_set_mreq:
- mreq_val.imr_multiaddr.s_addr = ival;
- mreq_val.imr_interface.s_addr = get_int32(ptr);
+ mreq_val.imr_multiaddr.s_addr = sock_htonl (ival);
+ mreq_val.imr_interface.s_addr = sock_htonl (get_int32(ptr));
ptr += 4;
len -= 4;
arg_ptr = (char*)&mreq_val;
Sam
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| sam at inf.enst.fr |
| Posted: Thu Dec 09, 1999 11:40 am |
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Guest
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>>>>> "Sam" == Samuel Tardieu <sam_at_inf.enst.fr> writes:
Sam> I just wrote the following patch, but may not have the time
Sam> to have it tested tonight (I have no Erlang semi-compiled
Sam> here).
After applying and testing it, it looks like multicast now works
fine.e I repost the (tiny) patch for inclusion in Erlang.
Sam
--
Samuel Tardieu -- sam_at_inf.enst.fr
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