Scapy中LLDP模块构造的数据包字节数异常问题求助

我使用scapy.contrib.lldp库构造LLDP数据包，包含以下字段：

• Chassis ID（l1）
• Port ID（l2）
• Time to live（l3）
• System name（l4）
• Generic Organisation Specific - 自定义数据1（l5）
• Generic Organisation Specific - 自定义数据2（l6）
• End of LLDP（l7）

所有字段的参数来自导入为DataFrame的CSV文件，通过库中对应的类构造每个字段。目前遇到的问题是：构造完成的数据包中，l6字段的字节数是预期值的两倍，即使设置固定值也无法解决这个问题。

Wireshark对比示例 #

DataFrame数据 #

相关代码 #

def getlldppack(host_2,ifa):
    lim = 1
    log = "/root/log.log"
    file = "/root/dic_"+str(host_2)+"_"+str(lim)+".csv"
    while lim<5:
        try:
            lldp1 = pd.read_csv(file)
        except:
            with open(log,'a') as lf:
                lf.write("error when reading the packet "+file+" for count "+str(lim)+"\n")
            time.sleep(8)
        else:
            lldp1 = lldp1.iloc[: , 1:]
            e1=lldp1.loc[(lldp1['Layer']=='Ethernet')&(lldp1['Field']=='dst')].iloc[0,2]
            e2=lldp1.loc[(lldp1['Layer']=='Ethernet')&(lldp1['Field']=='src')].iloc[0,2]
            e3=int(lldp1.loc[(lldp1['Layer']=='Ethernet')&(lldp1['Field']=='type')].iloc[0,2])
            e = Ether(dst=e1, src=e2, type=e3)
            a1=int(lldp1.loc[(lldp1['Layer']=='LLDPDUChassisID')&(lldp1['Field']=='_type')].iloc[0,2])
            a2=int(lldp1.loc[(lldp1['Layer']=='LLDPDUChassisID')&(lldp1['Field']=='_length')].iloc[0,2])
            a3=int(lldp1.loc[(lldp1['Layer']=='LLDPDUChassisID')&(lldp1['Field']=='subtype')].iloc[0,2])
            a4=lldp1.loc[(lldp1['Layer']=='LLDPDUChassisID')&(lldp1['Field']=='family')].iloc[0,2]
            a5=lldp1.loc[(lldp1['Layer']=='LLDPDUChassisID')&(lldp1['Field']=='id')].iloc[0,2]
            b1=int(lldp1.loc[(lldp1['Layer']=='LLDPDUPortID')&(lldp1['Field']=='_type')].iloc[0,2])
            b2=int(lldp1.loc[(lldp1['Layer']=='LLDPDUPortID')&(lldp1['Field']=='_length')].iloc[0,2])
            b3=int(lldp1.loc[(lldp1['Layer']=='LLDPDUPortID')&(lldp1['Field']=='subtype')].iloc[0,2])
            b4=lldp1.loc[(lldp1['Layer']=='LLDPDUPortID')&(lldp1['Field']=='family')].iloc[0,2]
            b5=int(lldp1.loc[(lldp1['Layer']=='LLDPDUPortID')&(lldp1['Field']=='id')].iloc[0,2])
            c1=int(lldp1.loc[(lldp1['Layer']=='LLDPDUTimeToLive')&(lldp1['Field']=='_type')].iloc[0,2])
            c2=int(lldp1.loc[(lldp1['Layer']=='LLDPDUTimeToLive')&(lldp1['Field']=='_length')].iloc[0,2])
            c3=int(lldp1.loc[(lldp1['Layer']=='LLDPDUTimeToLive')&(lldp1['Field']=='ttl')].iloc[0,2])
            d1=int(lldp1.loc[(lldp1['Layer']=='LLDPDUSystemName')&(lldp1['Field']=='_type')].iloc[0,2])
            d2=int(lldp1.loc[(lldp1['Layer']=='LLDPDUSystemName')&(lldp1['Field']=='_length')].iloc[0,2])
            d3=lldp1.loc[(lldp1['Layer']=='LLDPDUSystemName')&(lldp1['Field']=='system_name')].iloc[0,2])
            e1=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='_type')].iloc[0,2])
            e2=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='_length')].iloc[0,2])
            e3=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='org_code')].iloc[0,2])
            e4=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='subtype')].iloc[0,2])
            e5=lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='data')].iloc[0,2])
            f1=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='_type')].iloc[1,2])
            f2=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='_length')].iloc[1,2])
            f3=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='org_code')].iloc[1,2])
            f4=int(lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='subtype')].iloc[1,2])
            f5=lldp1.loc[(lldp1['Layer']=='LLDPDUGenericOrganisationSpecific')&(lldp1['Field']=='data')].iloc[1,2])
            g1=int(lldp1.loc[(lldp1['Layer']=='LLDPDUEndOfLLDPDU')&(lldp1['Field']=='_type')].iloc[0,2])
            g2=int(lldp1.loc[(lldp1['Layer']=='LLDPDUEndOfLLDPDU')&(lldp1['Field']=='_length')].iloc[0,2])
           
           
            l1 = LLDPDUChassisID(_type=a1,_length=a2,subtype=a3,family=a4,id=a5)
            l2 = LLDPDUPortID(_type=b1,_length=b2,subtype=b3,family=b4,id=str(b5))
            l3 = LLDPDUTimeToLive(_type=c1,_length=c2,ttl=c3)
            auxo=d3
            l4 = LLDPDUSystemName(_type=d1,_length=d2,system_name=auxo)
            auxo=e5
            l5 = LLDPDUGenericOrganisationSpecific(_type=e1,_length=e2,org_code=e3,subtype=e4,data=auxo)
            auxa=f5[2:-1]
            l6 = LLDPDUGenericOrganisationSpecific(_type=f1,_length=f2,org_code=f3,subtype=f4,data=auxa)
            l7 = LLDPDUEndOfLLDPDU(_type=0,_length=0)
            lldpu_layer = LLDPDU()
            lldpu_layer = l1/l2/l3/l4/l5/l6/l7
            
            pack = e/lldpu_layer
            
            flag = False
            sendp(pack,count=1, iface=ifa)
            flag = True
            lim = lim +1

            with open(log,'a') as lf:
                lf.write('read packet '+file+"\n")

我已经尝试修改数据类型、固定LLDPDUGenericOrganisationSpecific的data参数值，但都无法解决问题。目标是构造出与原始数据包完全一致、长度正确的LLDP数据包。

内容的提问来源于stack exchange，提问作者Juli