ipv4.py 文件源码

def serialize(self, payload, prev):
        length = len(self)
        hdr = bytearray(length)
        version = self.version << 4 | self.header_length
        flags = self.flags << 13 | self.offset
        if self.total_length == 0:
            self.total_length = self.header_length * 4 + len(payload)
        struct.pack_into(ipv4._PACK_STR, hdr, 0, version, self.tos,
                         self.total_length, self.identification, flags,
                         self.ttl, self.proto, 0,
                         addrconv.ipv4.text_to_bin(self.src),
                         addrconv.ipv4.text_to_bin(self.dst))

        if self.option:
            assert (length - ipv4._MIN_LEN) >= len(self.option)
            hdr[ipv4._MIN_LEN:ipv4._MIN_LEN + len(self.option)] = self.option

        self.csum = packet_utils.checksum(hdr)
        struct.pack_into('!H', hdr, 10, self.csum)
        return hdr