如何在 Erlang 中构建 DNS 查询记录？

发布于 2024-08-11 09:50:33 字数 525 浏览 5 评论 0原文

我正在构建一个本机 Bonjour / Zeroconf 库，并且需要构建 DNS 查询记录以广播到其他计算机。我尝试过查看 Erlang 源代码，但由于我对 Erlang 比较陌生，它在所有 inet_XXX.erl 和 .hrl 文件的内部变得有点密集。我有一个用于接收和解析 DNS 记录有效负载的侦听器，但我只是不知道如何创建查询记录。我真正需要知道的是我需要传递给 inet_dns:encode() 以获得可以发送的二进制文件。这就是我正在尝试做的事情。

{ok,P} = inet_dns:encode(#dns_query{domain="_daap._tcp.local",type=ptr,class=in})

这是我收到的错误

10> test:send().
** exception error: {badrecord,dns_rec}
     in function  inet_dns:encode/1
     in call from test:send/0
11>

原文

I am building a native Bonjour / Zeroconf library and need to build DNS query records to broadcast off to the other machines. I have tried looking thru the Erlang source code but as I am relatively new to Erlang it gets kind of dense down the bowels of all the inet_XXX.erl and .hrl files. I have a listener that works for receiving and parsing the DNS record payloads, I just can't figure out how to create the query records. What I really need to know is what I need to pass into inet_dns:encode() to get a binary I can send out. Here is what I am trying to do.

{ok,P} = inet_dns:encode(#dns_query{domain="_daap._tcp.local",type=ptr,class=in})

here is the error I am getting

10> test:send().
** exception error: {badrecord,dns_rec}
     in function  inet_dns:encode/1
     in call from test:send/0
11>

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≈。彩虹 2024-08-18 09:50:33

我终于想通了。

send(Domain) ->
    {ok,S} = gen_udp:open(5555,[{reuseaddr,true}, {ip,{224,0,0,251}}, {multicast_ttl,4}, {multicast_loop,false}, {broadcast,true}, binary]),
    P = #dns_rec{header=#dns_header{},qdlist=[#dns_query{domain=Domain,type=ptr,class=in}]},
    gen_udp:send(S,{224,0,0,251},5353,inet_dns:encode(P)),
    gen_udp:close(S).

I finally figured it out.

send(Domain) ->
    {ok,S} = gen_udp:open(5555,[{reuseaddr,true}, {ip,{224,0,0,251}}, {multicast_ttl,4}, {multicast_loop,false}, {broadcast,true}, binary]),
    P = #dns_rec{header=#dns_header{},qdlist=[#dns_query{domain=Domain,type=ptr,class=in}]},
    gen_udp:send(S,{224,0,0,251},5353,inet_dns:encode(P)),
    gen_udp:close(S).

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