ejabberd_s2s

作为gen_server启动

初始化时创建s2s（mnesia）表，保存的是服务器之间的联系信息，server和server之间的路由

主要为do_route(From, To, Packet)方法

do_route(From, To, Packet) ->
    ?DEBUG("s2s manager~n\tfrom ~p~n\tto ~p~n\tpacket "
       "~P~n",
       [From, To, Packet, 8]),
    case find_connection(From, To) of
      {atomic, Pid} when is_pid(Pid) ->
      ?DEBUG("sending to process ~p~n", [Pid]),
      #xmlel{name = Name, attrs = Attrs, children = Els} =
          Packet,
      NewAttrs =
          jlib:replace_from_to_attrs(jid:to_string(From),
                     jid:to_string(To), Attrs),
      #jid{lserver = MyServer} = From,
      ejabberd_hooks:run(s2s_send_packet, MyServer,
                 [From, To, Packet]),
      send_element(Pid,
               #xmlel{name = Name, attrs = NewAttrs, children = Els}),
      ok;
      {aborted, _Reason} ->
      case xml:get_tag_attr_s(<<"type">>, Packet) of
        <<"error">> -> ok;
        <<"result">> -> ok;
        _ ->
        Err = jlib:make_error_reply(Packet,
                        ?ERR_SERVICE_UNAVAILABLE),
        ejabberd_router:route(To, From, Err)
      end,
      false
    end.

首先根据from，to在s2s里面查找是否存在路由find_connection(From, To)

如找到则返回存在的pid

如果没找到则利用open_several_connections函数创建：

启动一个ejabberd_s2s_out进程去建立连接，并把建立的信息和pid保存到s2s里面，方便下次路由用到

其中ejabberd_s2s_out作为ejabberd_s2s_out_sup的子进程，连接到别的节点开启的ejabberd_s2s_in 服务（默认开启三个监听接口ejabberd_c2s、ejabberd_s2s_in、ejabberd_http）