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Purports to support multicast DNS and DNS-SD in Erlang.
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Only supports one off queries. Will do more later, with any luck.
Early commit, makes it easier to share between workstations.
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@msantos
msantos committed Feb 9, 2010
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3 changes: 3 additions & 0 deletions .gitignore
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*.[oa]
*.beam
.*.swp
6 changes: 6 additions & 0 deletions Emakefile
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{["src/*"],
[{i, "include"},
{outdir, "ebin"},
debug_info]
}.

16 changes: 16 additions & 0 deletions Makefile
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ERL=erl
APP=emdns

all: dir erl

dir:
-@mkdir -p priv/tmp ebin

erl:
@$(ERL) -noinput +B \
-eval 'case make:all() of up_to_date -> halt(0); error -> halt(1) end.'

clean:
@rm -fv ebin/*.beam

54 changes: 54 additions & 0 deletions README
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emdns is a cleverly named implementation of the multicast DNS (aka
Bonjour, aka ZeroConf) and DNS-SD (DNS Service Discovery) protocols
for Erlang.

Eventually, it will support:

http://files.multicastdns.org/draft-cheshire-dnsext-multicastdns.txt


BUILD

make


QUICK START

Assume you have two hosts "nul" and "ack". Any multicast DNS services
are disabled on "nul". "ack" runs Mac OS X.

Host Entry

1. Login to "ack". From a shell, run:

$ ping nul.local
ping: unknown host nul.local

2. On "nul", start erl:

$ erl -pa ebin
> emdns_server:start().
{ok,<0.35.0>}
> emdns_server:debug(true).
ok
> A = emdns:service(host). % assumes "nul" has a reverse DNS entry
<<0,0,132,...>>
> emdns_server:send(A).
ok

3. On "ack", run:

$ ping nul.local
PING nul.local (192.168.1.10): 56 data bytes
64 bytes from 192.168.1.10: icmp_seq=0 ttl=64 time=4.471 ms
64 bytes from 192.168.1.10: icmp_seq=1 ttl=64 time=2.611 ms

4. Set up a DAAP service

> D = emdns:service(daap).
> emdns_server:send(D).

5. On "ack", in iTunes, check "Devices" for a entry named "erlMOTE".


52 changes: 52 additions & 0 deletions include/emdns.hrl
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%% Copyright (c) 2010, Michael Santos <michael.santos@gmail.com>
%% All rights reserved.
%%
%% Redistribution and use in source and binary forms, with or without
%% modification, are permitted provided that the following conditions
%% are met:
%%
%% Redistributions of source code must retain the above copyright
%% notice, this list of conditions and the following disclaimer.
%%
%% Redistributions in binary form must reproduce the above copyright
%% notice, this list of conditions and the following disclaimer in the
%% documentation and/or other materials provided with the distribution.
%%
%% Neither the name of the author nor the names of its contributors
%% may be used to endorse or promote products derived from this software
%% without specific prior written permission.
%%
%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
%% "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
%% LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
%% FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
%% COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
%% INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
%% BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
%% LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
%% CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
%% LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
%% ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
%% POSSIBILITY OF SUCH DAMAGE.

-include_lib("kernel/src/inet_dns.hrl").

-define(MDNS_PORT, 5353).
-define(MDNS_ADDRESS, {224,0,0,251}).

-define(TRUE, 1).
-define(FALSE, 0).

% XXX some of the encoding functions in inet_dns match
% XXX on class 'in'. Using CLASS_CF will cause the
% XXX decoding to fail.
% XXX
% XXX Either grovel through the binary returned by inet_dns:encode/1
% XXX and manually replace the value (ewww) or make a copy of inet_dns
% XXX and modify it.
-define(CLASS_CF, 32769). % CLASS: cache flush: class IN, with top bit set to 1

-define(TYPE_NSEC, 47). % TYPE: NSEC, negate, used to indicate a AAAA does not
% exist for the host


233 changes: 233 additions & 0 deletions src/emdns.erl
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%% Copyright (c) 2010, Michael Santos <michael.santos@gmail.com>
%% All rights reserved.
%%
%% Redistribution and use in source and binary forms, with or without
%% modification, are permitted provided that the following conditions
%% are met:
%%
%% Redistributions of source code must retain the above copyright
%% notice, this list of conditions and the following disclaimer.
%%
%% Redistributions in binary form must reproduce the above copyright
%% notice, this list of conditions and the following disclaimer in the
%% documentation and/or other materials provided with the distribution.
%%
%% Neither the name of the author nor the names of its contributors
%% may be used to endorse or promote products derived from this software
%% without specific prior written permission.
%%
%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
%% "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
%% LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
%% FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
%% COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
%% INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
%% BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
%% LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
%% CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
%% LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
%% ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
%% POSSIBILITY OF SUCH DAMAGE.

-module(emdns).

-include_lib("kernel/include/inet.hrl").
-include("emdns.hrl").

-define(TTL_SHORT, 120).
-define(TTL_LONG, 4500).

-export([ttl/1, type/1, encode/1, service/1]).
-export([hostname/0,local_address/0,reverse_address/1]).


%%%
%%% Record construction
%%%
ttl(short) ->
?TTL_SHORT;
ttl(long) ->
?TTL_LONG.


type(header) ->
% standard, authoritative mdns header
#dns_header{
id = 0,
opcode = ?QUERY,
aa = ?TRUE, % authoritative
qr = ?TRUE % response flag
};

type({ptr, L}) when is_list(L) ->
Domain = proplists:get_value(domain, L, reverse_address(local_address())),
Class = proplists:get_value(class, L, in),
TTL = proplists:get_value(ttl, L, ?TTL_SHORT),
Data = proplists:get_value(data, L, hostname()),

#dns_rr{
domain = Domain,
type = ptr,
class = Class,
ttl = TTL,
data = Data
};

type({srv, L}) when is_list(L) ->
Domain = proplists:get_value(domain, L, hostname()),
Class = proplists:get_value(class, L, in),
TTL = proplists:get_value(ttl, L, ?TTL_SHORT),
Data = proplists:get_value(data, L, hostname()),

case Data of
{A,B,C,D} when is_integer(A), is_integer(B), is_integer(C), is_list(D) ->
#dns_rr{
domain = Domain,
type = srv,
class = Class,
ttl = TTL,
data = {0,0,1024,"nul.local"}
};
_ ->
{err, fmt}
end;

type({txt, L}) when is_list(L) ->
Domain = proplists:get_value(domain, L, hostname()),
Class = proplists:get_value(class, L, in), % should be cache flush
TTL = proplists:get_value(ttl, L, ?TTL_LONG),
Data = proplists:get_value(data, L, []),

case Data of
Any when is_list(Any) ->
#dns_rr{
domain = Domain,
type = txt,
class = Class,
ttl = TTL,
data = Data
};
_ ->
{err, fmt}
end;

type({a, L}) when is_list(L) ->
Domain = proplists:get_value(domain, L, hostname()),
Class = proplists:get_value(class, L, in),
TTL = proplists:get_value(ttl, L, ?TTL_SHORT),
{IP1,IP2,IP3,IP4} = proplists:get_value(data, L, local_address()),

#dns_rr{
domain = Domain,
type = a,
class = Class,
ttl = TTL,
data = <<IP1,IP2,IP3,IP4>>
};

type({any, L}) when is_list(L) ->
Domain = proplists:get_value(domain, L, hostname()),
Class = proplists:get_value(class, L, in),
TTL = proplists:get_value(ttl, L, ?TTL_SHORT),

#dns_rr{
domain = Domain,
type = any,
class = Class,
ttl = TTL
}.


encode(L) when is_list(L) ->
Header = proplists:get_value(header, L, type(header)),
Queries = proplists:get_value(queries, L, []),
Answers = proplists:get_value(answers, L, []),
Resources = proplists:get_value(resources, L, []),

Record = #dns_rec{
header = Header,
qdlist = Queries,
anlist = Answers,
arlist = Resources
},
inet_dns:encode(Record).


%%%
%%% Services
%%%
service(probe) ->
Any = type({any, [{class, ?CLASS_CF}]}),
encode([{answers, [Any]}]);

service(host) ->
A = type({a, [{class, ?CLASS_CF}]}),
encode([{answers, [A]}]);

% See:
% http://dacp.jsharkey.org/
% http://blog.mycroes.nl/2008/08/pairing-itunes-remote-app-with-your-own.html
service(daap) ->
Service = "0000000000000000000000000000000000000011._touch-remote._tcp.local",
Domain = "nul.local",
Hostname = hostname(),
IP = local_address(),

PTR = type({ptr, [
{domain, "_touch-remote._tcp.local"},
{ttl, ?TTL_LONG},
{data, Service}
]}),

TXT = type({txt, [
{domain, Service},
{ttl, 4500},
{data, [
"DvNm=erlMOTE",
"RemV=10000",
"DvTy=iPod",
"RemN=Remote",
"txtvers=1",
"Pair=0000000000000011"
]}
]}),

SRV = type({srv, [
{domain, Service},
{data, {0,0,1024,Hostname}} % XXX should allow setting port
]}),

A = type({a, [
{domain, Domain},
{class, ?CLASS_CF},
{data, IP}
]}),

encode([{answers, [PTR, TXT, SRV, A]}]).


%%
%% Utilities
%%

reverse_address(Addr) when is_tuple(Addr) ->
% 212.213.168.192.in-addr.arpa
lists:flatten([ integer_to_list(N) ++ "." ||
N <- lists:reverse(tuple_to_list(Addr)) ]
++ "in-addr.arpa").


%%
%% Defaults
%%

hostname() ->
% inet:gethostname/0 will never fail
hd(string:tokens(element(2,inet:gethostname()), ".")) ++ ".local".

local_address() ->
Host = element(2, inet:gethostname()),
{ok, HE} = inet:gethostbyname(Host),
hd(HE#hostent.h_addr_list).


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