Q:

Not a pcap capture file (bad magic) - scapy python

I've got problem trying open .pcap file. In scapy.utils there is RawPcapReader
    try:
        self.f = gzip.open(filename,"rb")
        magic = self.f.read(4)
    except IOError:
        self.f = open(filename,"rb")
        magic = self.f.read(4)
    if magic == "\xa1\xb2\xc3\xd4": #big endian
        self.endian = ">"
    elif  magic == "\xd4\xc3\xb2\xa1": #little endian
        self.endian = "<"
    else:
        raise Scapy_Exception("Not a pcap capture file (bad magic)")
    hdr = self.f.read(20)
    if len(hdr)<20:
        raise Scapy_Exception("Invalid pcap file (too short)")

My magic has value "\n\r\r\n" but RawPcapReader is expecting  magic == "\xa1\xb2\xc3\xd4" or magic == "\xd4\xc3\xb2\xa1".
Could you tell me what can be the problem? With .pcap file? I'm using python version 2.7

A:

The magic value of "\n\r\r\n" (\x0A\x0D\x0D\x0A) indicates that your file is actually in .pcapng format, rather than libpcap 
The solution is simple
In Wireshark 'Save As': Wireshark/tcpdump - pcap
Or use tshark:
$tshark -r old.pcapng -w new.pcap -F libpcap

