title: Scapy: no reply on raw ICMP packet
body: <p>I've constructed a packet with <code>scapy</code>:</p>
  
  <pre><code>a=IP(dst='192.168.0.1',proto=1)/'\x08\x00\xf7\xff\x00\x00\x00\x00'
  </code></pre>
  
  <p>I run:</p>
  
  <pre><code>send(a)
  </code></pre>
  
  <p>Wireshark shows me that there is a ping request and ping response from 192.168.0.1
  No warnings, all fields are correct</p>
  
  <p>But when I try:</p>
  
  <pre><code>b=sr1(a)
  </code></pre>
  
  <p>Then Scapy can't get an answer (Wireshark shows me again that there is request and reply)</p>
  
  <p>What can I do with it?</p>