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    af_unix: implement socket filter · d6ae3bae
    Alban Crequy 提交于
    Linux Socket Filters can already be successfully attached and detached on unix
    sockets with setsockopt(sockfd, SOL_SOCKET, SO_{ATTACH,DETACH}_FILTER, ...).
    See: Documentation/networking/filter.txt
    
    But the filter was never used in the unix socket code so it did not work. This
    patch uses sk_filter() to filter buffers before delivery.
    
    This short program demonstrates the problem on SOCK_DGRAM.
    
    int main(void) {
      int i, j, ret;
      int sv[2];
      struct pollfd fds[2];
      char *message = "Hello world!";
      char buffer[64];
      struct sock_filter ins[32] = {{0,},};
      struct sock_fprog filter;
    
      socketpair(AF_UNIX, SOCK_DGRAM, 0, sv);
    
      for (i = 0 ; i < 2 ; i++) {
        fds[i].fd = sv[i];
        fds[i].events = POLLIN;
        fds[i].revents = 0;
      }
    
      for(j = 1 ; j < 13 ; j++) {
    
        /* Set a socket filter to truncate the message */
        memset(ins, 0, sizeof(ins));
        ins[0].code = BPF_RET|BPF_K;
        ins[0].k = j;
        filter.len = 1;
        filter.filter = ins;
        setsockopt(sv[1], SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));
    
        /* send a message */
        send(sv[0], message, strlen(message) + 1, 0);
    
        /* The filter should let the message pass but truncated. */
        poll(fds, 2, 0);
    
        /* Receive the truncated message*/
        ret = recv(sv[1], buffer, 64, 0);
        printf("received %d bytes, expected %d\n", ret, j);
      }
    
        for (i = 0 ; i < 2 ; i++)
          close(sv[i]);
    
      return 0;
    }
    Signed-off-by: NAlban Crequy <alban.crequy@collabora.co.uk>
    Reviewed-by: NIan Molton <ian.molton@collabora.co.uk>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    d6ae3bae
af_unix.c 54.1 KB