关于打断点的问题?

PF_FORWARD_ACTION
IpFilterHook(
unsigned char   *PacketHeader,
unsigned char   *Packet,
unsigned int    PacketLength,
unsigned int    RecvInterfaceIndex,
unsigned int    SendInterfaceIndex,
IPAddr          RecvLinkNextHop,
IPAddr          SendLinkNextHop
)
{
DebugPrintMsg(\"ZFfiltering\");
unsigned char a=0,b=0;
    if(((IPHeader *)PacketHeader)->iph_protocol == PROT_TCP)
    {
unsigned char swap=Packet[0];
a=swap<<4;
a=swap>>4;
b=swap>>4;
    }
    return PF_FORWARD;
}
为什么只有  return PF_FORWARD;这一句可以打断点