포트 53에서 언바운드 수신 대기 방법 이해

Question

Debian Buster에 언바운드를 설치했습니다. 이제 언바운드가 각 프로토콜을 2번씩 수신하는 이유가 궁금합니다.

netstat -tulpn

tcp        0      0 0.0.0.0:53              0.0.0.0:*               LISTEN      1150/unbound        
tcp        0      0 0.0.0.0:53              0.0.0.0:*               LISTEN      1150/unbound        
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      605/sshd: /usr/sbin 
tcp        0      0 127.0.0.1:8953          0.0.0.0:*               LISTEN      1150/unbound        
tcp6       0      0 :::22                   :::*                    LISTEN      605/sshd: /usr/sbin 
udp        0      0 0.0.0.0:53              0.0.0.0:*                           1150/unbound        
udp        0      0 0.0.0.0:53              0.0.0.0:*                           1150/unbound   

누구든지 내가 이것을 이해하도록 도와줄 수 있나요?

Answer 1

언바운드는SO_REUSEPORT여러/프로세스 스레드가 동일한 수신 포트를 공유하도록 허용하는 옵션입니다.

SO_REUSEPORT(since Linux 3.9)

          Permits multiple AF_INET or AF_INET6 sockets to be bound
          to an identical socket address.  This option must be set
          on each socket (including the first socket) prior to
          calling bind(2) on the socket.  To prevent port hijacking,
          all of the processes binding to the same address must have
          the same effective UID.  This option can be employed with
          both TCP and UDP sockets.

          For TCP sockets, this option allows accept(2) load
          distribution in a multi-threaded server to be improved by
          using a distinct listener socket for each thread.  This
          provides improved load distribution as compared to
          traditional techniques such using a single accept(2)ing
          thread that distributes connections, or having multiple
          threads that compete to accept(2) from the same socket.

          For UDP sockets, the use of this option can provide better
          distribution of incoming datagrams to multiple processes
          (or threads) as compared to the traditional technique of
          having multiple processes compete to receive datagrams on
          the same socket.