Why is the encoding mode of 'ifreq' 16s16x?

[Orobas-D]

Sorry, I'm a beginner, I'm just curious, but I noticed that in the <if.h> header file, the 'ifreq' structure can be 16 bytes. Why is there still a need to fill in 16 empty bytes?Is it because of compatibility issues?
scapy.arch.bpf.supersocket. _L2bpfSocket

try:
    fcntl.ioctl(
        self.bpf_fd, BIOCSETIF,
        struct.pack("16s16x", self.iface.encode())
     )
except IOError:
     raise Scapy_Exception("BIOCSETIF failed on %s" % self.iface)
     self.assigned_interface = self.iface

It seems that changing it to the following format also works fine.

try:
    fcntl.ioctl(
        self.bpf_fd, BIOCSETIF,
        struct.pack(str(len(self.iface)) + "s", self.iface.encode())
     )
except IOError:
     raise Scapy_Exception("BIOCSETIF failed on %s" % self.iface)
     self.assigned_interface = self.iface

MacOS:14.4

[gpotter2]

Hi,
Please note that this is not a forum but a bugtracker. Please ask your question on the gitter or on stack overflow.
Thanks for your understanding