如何获取所需广播地址的发件人IP：端口组合？

Question

我在Wireshark上看到了一些广播数据包，我希望能够使用希望成为简单的Linux命令行实用程序的东西进行检查。它看起来像这样：

getsenders bcast_IP port timeout 

它只会打印在超时期间遇到的每个新的发件人IP。

例如：

getsenders 192.168.0.255 12345 0.150 

或（可替换地）

getsenders 192.168.0.0/8 12345 0.150 

将侦听发送到192.168.0.255:12345广播报文，然后打印遇到的每个独特的发送者。在指定界面上列出任何广播发送者的替代方法。

不幸的是，我的socket-fu很弱。我所知道的是，程序必须以root权限运行（suid）来监听广播套接字。

我已经花了很多时间（天）试图从Python做到这一点，但它看起来像这条路线将需要使用原始套接字和解析数据包（嗅探器，呃！）。我也看着使用socat/netcat（通过一个只执行suid bash脚本），但也没有得到。

是否有一些简单的Linux代码可以为我做这个？我不在乎工具或源语言是什么，只要它可以设置为suid-root并从命令行运行即可。

顺便说一句，我有一个简单的Python的解决方案，微软Windows下工作，但死在Linux下：

myip = <IP address of local interface to listen on> 
p = <broadcast port> 
timeout = 0.150 # 150 ms 
addresses = {} 

if "windows" in sys.platform.tolower(): 
    # Create the broadcast reception socket 
    bsock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) 
    bsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) 
    bsock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1) 
    bsock.settimeout(timeout) 
    bsock.bind((myip, p)) 
    while True: # Look for all senders 
     try: 
      __, address = bsock.recvfrom(1024) # Don't care about payload 
     except BaseException, e: 
      break # Nothing found 
     else: # A desired broadcast packet was detected 
      if address[0] not in addresses: 
       addresses[address[0]] = 1 
      else: 
       addresses[address[0]] += 1 
       if addresses[address[0]] >= 3: 
        break # Go until timeout or any sender is seen 3 times 
     finally: 
      bsock.close() 
      bsock = None 
      print(', '.join([k for k in addresses])) 

Answer 1

下载和测试的许多例子之后，我终于得到了它的工作，然后一分为二并结合代码，直到我在两个平台上都有很小的差别。

它只涉及到一行：Linux必须绑定到特定的广播地址（以root身份），Windows可以绑定到广播数据包预计到达的本地接口地址（作为普通用户）。

下面是修改后的代码片段：

bcast_addr = <IP addr of broadcast: Must end with at least one '.255'> 
myip = <IP addr of local interface receiving from bcast_addr> 
p = <broadcast port> 
timeout = 0.150 # 150 ms 
addresses = {} 

# Create the broadcast reception socket 
bsock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) 
bsock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) 
bsock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1) 
bsock.settimeout(timeout) 
if "windows" in sys.platform.tolower(): 
    bsock.bind((myip, p)) 
elif os.getuid() == 0: # Must be root for Linux! 
    bsock.bind((bcast_addr, p)) 
while True: # Look for all senders 
    try: 
     __, address = bsock.recvfrom(1024) # Don't care about payload 
    except BaseException, e: 
     break # Nothing found 
    else: # A desired broadcast packet was detected 
     if address[0] not in addresses: 
      addresses[address[0]] = 1 
     else: 
      addresses[address[0]] += 1 
      if addresses[address[0]] >= 3: 
       break # Go until timeout or any sender is seen 3 times 
    finally: 
     bsock.close() 
     bsock = None 
     print(', '.join([k for k in addresses]))