我正在实现基于netfilter_queue的用户程序，该程序将删除ipv4可选标头“时间戳”

ping在此程序中效果很好，因为它使用 ICMP 传输。

但是基于TCP 的应用程序不起作用。我已经用Wireshark进行了检查，该程序很好地删除了时间戳。相反，基于TCP的应用程序不会为该数据包发送ACK，并且远程服务器会无限期地重新传输同一数据包。

TCP数据包处理是否缺少任何程序？我只修改了IPv4标头部分。那么为什么tcp传输根本不起作用？

我的主要代码是：

static int cb(struct nfq_q_handle *qh,struct nfgenmsg *nfmsg,struct nfq_data *nfa,void *data)
{
    
    unsigned int timestamp = 0;
    bool ptype = true;
    int pnow = 20;
    int plast = 20;
    int ihl;
    
    struct nfqnl_msg_packet_hdr *ph = nfq_get_msg_packet_hdr(nfa);

    unsigned char* rawBuff = NULL;
    int len;
    len = nfq_get_payload(nfa,&rawBuff);
    if(len < 0) printf("Failed to get payload");

    struct pkt_buff* pkBuff = pktb_alloc(AF_INET,rawBuff,len,0x20);
    struct iphdr* ip = nfq_ip_get_hdr(pkBuff);
    
    ihl = ip->ihl;
    uint8_t* buff = NULL;
    
    if( (ip->daddr != 0x0101007f) && (ip->daddr != 0x0100007f) && (ip->daddr != 0x0100A9C0) && (ip->saddr != 0x0100A9C0)) { // filter_out dns
        if(ip->version == 4) {
            if(ihl != 5) { // if ipv4 packet header is longer than default packet header
                buff = pktb_data(pkBuff); // packet buffer
                plast = ihl * 4;
                while(pnow != plast) {
                    if(buff[pnow] == 0x44) { // timestamp type
                        ptype = false;
                        break;
                    }
                    else {
                        if(buff[pnow+1] == 0) {
                            pnow = pnow + 4;
                        }
                        else {
                            pnow = pnow + buff[pnow+1];
                        }
                    }
                }
            }
            if(!ptype) {
                timestamp = buff[pnow + 4] << 24 | buff[pnow + 5] << 16 | buff[pnow + 6] << 8 | buff[pnow + 7];
                if(timestamp > 100000) { // if TS is big,delete it.
                    ip->ihl -= 2;
                    nfq_ip_mangle(pkBuff,pnow,8,"",0);
                }
            }
        }
    }
    
    nfq_ip_set_checksum(ip);
    if(nfq_ip_set_transport_header(pkBuff,ip) < 0) printf("Failed to set transport header");

    int result = 0;
    result = nfq_set_verdict(qh,ntohl(ph->packet_id),NF_accEPT,pktb_len(pkBuff),pktb_data(pkBuff));
    pktb_free(pkBuff);
    return result;
}

iptables设置为：

sudo iptables -t mangle -A PREROUTING -j NFQUEUE -p all --queue-num 0
sudo iptables -t mangle -A POSTROUTING -j NFQUEUE -p all --queue-num 0