tinyfecVPN/tun_dev.cpp

/*
 * tun.cpp
 *
 *  Created on: Oct 26, 2017
 *      Author: root
 */

#include "tun_dev.h"

my_time_t last_keep_alive_time = 0;

int get_tun_fd(char *dev_name) {
    int tun_fd = open("/dev/net/tun", O_RDWR);

    if (tun_fd < 0) {
        mylog(log_fatal, "open /dev/net/tun failed");
        myexit(-1);
    }
    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    ifr.ifr_flags = IFF_TUN | IFF_NO_PI;

    strncpy(ifr.ifr_name, dev_name, IFNAMSIZ);

    if (ioctl(tun_fd, TUNSETIFF, (void *)&ifr) != 0) {
        mylog(log_fatal, "open /dev/net/tun failed");
        myexit(-1);
    }

    if (persist_tun == 1) {
        if (ioctl(tun_fd, TUNSETPERSIST, 1) != 0) {
            mylog(log_warn, "failed to set tun persistent");
        }
    }
    return tun_fd;
}

int set_tun(char *if_name, u32_t local_ip, u32_t remote_ip, int mtu) {
    if (manual_set_tun) return 0;

    // printf("i m here1\n");
    struct ifreq ifr;
    struct sockaddr_in sai;
    memset(&ifr, 0, sizeof(ifr));
    memset(&sai, 0, sizeof(struct sockaddr));

    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    strncpy(ifr.ifr_name, if_name, IFNAMSIZ);

    sai.sin_family = AF_INET;
    sai.sin_port = 0;

    sai.sin_addr.s_addr = local_ip;
    memcpy(&ifr.ifr_addr, &sai, sizeof(struct sockaddr));
    assert(ioctl(sockfd, SIOCSIFADDR, &ifr) == 0);  // set source ip

    sai.sin_addr.s_addr = remote_ip;
    memcpy(&ifr.ifr_addr, &sai, sizeof(struct sockaddr));
    assert(ioctl(sockfd, SIOCSIFDSTADDR, &ifr) == 0);  // set dest ip

    ifr.ifr_mtu = mtu;
    assert(ioctl(sockfd, SIOCSIFMTU, &ifr) == 0);  // set mtu

    assert(ioctl(sockfd, SIOCGIFFLAGS, &ifr) == 0);
    // ifr.ifr_flags |= ( IFF_UP|IFF_POINTOPOINT|IFF_RUNNING|IFF_NOARP|IFF_MULTICAST );
    ifr.ifr_flags = (IFF_UP | IFF_POINTOPOINT | IFF_RUNNING | IFF_NOARP | IFF_MULTICAST);  // set interface flags
    assert(ioctl(sockfd, SIOCSIFFLAGS, &ifr) == 0);

    // printf("i m here2\n");
    return 0;
}

int put_header(char header, char *data, int &len) {
    assert(len >= 0);
    data[len] = header;
    len += 1;
    return 0;
}
int get_header(char &header, char *data, int &len) {
    assert(len >= 0);
    if (len < 1) return -1;
    len -= 1;
    header = data[len];

    return 0;
}
int from_normal_to_fec2(conn_info_t &conn_info, dest_t &dest, char *data, int len, char header) {
    int out_n;
    char **out_arr;
    int *out_len;
    my_time_t *out_delay;

    from_normal_to_fec(conn_info, data, len, out_n, out_arr, out_len, out_delay);

    for (int i = 0; i < out_n; i++) {
        char tmp_buf[buf_len];
        int tmp_len = out_len[i];
        memcpy(tmp_buf, out_arr[i], out_len[i]);
        put_header(header, tmp_buf, tmp_len);
        delay_send(out_delay[i], dest, tmp_buf, tmp_len);  // this is slow but safer.just use this one

        // put_header(header,out_arr[i],out_len[i]);//modify in place
        // delay_send(out_delay[i],dest,out_arr[i],out_len[i]);//warning this is currently okay,but if you modified fec encoder,you  may have to use the above code
    }
    return 0;
}

int from_fec_to_normal2(conn_info_t &conn_info, dest_t &dest, char *data, int len) {
    int out_n;
    char **out_arr;
    int *out_len;
    my_time_t *out_delay;

    from_fec_to_normal(conn_info, data, len, out_n, out_arr, out_len, out_delay);

    for (int i = 0; i < out_n; i++) {
#if 0
        if (program_mode == server_mode) {
            char *tmp_data = out_arr[i];
            int tmp_len = out_len[i];
            iphdr *iph;
            iph = (struct iphdr *)tmp_data;
            if (tmp_len >= int(sizeof(iphdr)) && iph->version == 4) {
                u32_t dest_ip = iph->daddr;
                // printf("%s\n",my_ntoa(dest_ip));
                if ((ntohl(sub_net_uint32) & 0xFFFFFF00) != (ntohl(dest_ip) & 0xFFFFFF00)) {
                    string sub = my_ntoa(dest_ip);
                    string dst = my_ntoa(htonl(ntohl(sub_net_uint32) & 0xFFFFFF00));
                    mylog(log_warn, "[restriction]packet's dest ip [%s] not in subnet [%s],dropped, maybe you need to compile an un-restricted server\n", sub.c_str(), dst.c_str());
                    continue;
                }
            }
        }
#endif
        delay_send(out_delay[i], dest, out_arr[i], out_len[i]);
    }

    return 0;
}
int do_mssfix(char *s, int len)  // currently only for ipv4
{
    if (mssfix == 0) {
        return 0;
    }

    if (len < int(sizeof(iphdr))) {
        mylog(log_debug, "packet from tun len=%d <20\n", len);
        return -1;
    }
    iphdr *iph;
    iph = (struct iphdr *)s;
    if (iph->version != 4) {
        // mylog(log_trace,"not ipv4");
        return 0;
    }

    if (iph->protocol != IPPROTO_TCP) {
        // mylog(log_trace,"not tcp");
        return 0;
    }

    int ip_len = ntohs(iph->tot_len);
    int ip_hdr_len = iph->ihl * 4;

    if (len < ip_hdr_len) {
        mylog(log_debug, "len<ip_hdr_len,%d %d\n", len, ip_hdr_len);
        return -1;
    }
    if (len < ip_len) {
        mylog(log_debug, "len<ip_len,%d %d\n", len, ip_len);
        return -1;
    }
    if (ip_hdr_len > ip_len) {
        mylog(log_debug, "ip_hdr_len<ip_len,%d %d\n", ip_hdr_len, ip_len);
        return -1;
    }

    if ((ntohs(iph->frag_off) & (short)(0x1FFF)) != 0) {
        // not first segment

        // printf("line=%d %x  %x \n",__LINE__,(u32_t)ntohs(iph->frag_off),u32_t( ntohs(iph->frag_off) &0xFFF8));
        return 0;
    }
    if ((ntohs(iph->frag_off) & (short)(0x80FF)) != 0) {
        // not whole segment
        // printf("line=%d   \n",__LINE__);
        return 0;
    }

    char *tcp_begin = s + ip_hdr_len;
    int tcp_len = ip_len - ip_hdr_len;

    if (tcp_len < 20) {
        mylog(log_debug, "tcp_len<20,%d\n", tcp_len);
        return -1;
    }

    tcphdr *tcph = (struct tcphdr *)tcp_begin;

    if (int(tcph->syn) == 0)  // fast fail
    {
        mylog(log_trace, "tcph->syn==0\n");
        return 0;
    }

    int tcp_hdr_len = tcph->doff * 4;

    if (tcp_len < tcp_hdr_len) {
        mylog(log_debug, "tcp_len <tcp_hdr_len, %d %d\n", tcp_len, tcp_hdr_len);
        return -1;
    }

    /*
    if(tcp_hdr_len==20)
    {
        //printf("line=%d\n",__LINE__);
        mylog(log_trace,"no tcp option\n");
        return 0;
    }*/

    char *ptr = tcp_begin + 20;
    char *option_end = tcp_begin + tcp_hdr_len;
    while (ptr < option_end) {
        if (*ptr == 0) {
            return 0;
        } else if (*ptr == 1) {
            ptr++;
        } else if (*ptr == 2) {
            if (ptr + 1 >= option_end) {
                mylog(log_debug, "invaild option ptr+1==option_end,for mss\n");
                return -1;
            }
            if (*(ptr + 1) != 4) {
                mylog(log_debug, "invaild mss len\n");
                return -1;
            }
            if (ptr + 3 >= option_end) {
                mylog(log_debug, "ptr+4>option_end for mss\n");
                return -1;
            }
            int mss = read_u16(ptr + 2);  // uint8_t(ptr[2])*256+uint8_t(ptr[3]);
            int new_mss = mss;
            if (new_mss > ::mssfix - 40 - 10)  // minus extra 10 for safe
            {
                new_mss = ::mssfix - 40 - 10;
            }
            write_u16(ptr + 2, (unsigned short)new_mss);

            pseudo_header psh;

            psh.source_address = iph->saddr;
            psh.dest_address = iph->daddr;
            psh.placeholder = 0;
            psh.protocol = iph->protocol;
            psh.tcp_length = htons(tcp_len);

            tcph->check = 0;
            tcph->check = tcp_csum(psh, (unsigned short *)tcph, tcp_len);

            mylog(log_trace, "mss=%d  syn=%d ack=%d, changed mss to %d \n", mss, (int)tcph->syn, (int)tcph->ack, new_mss);

            // printf("test=%x\n",u32_t(1));
            // printf("frag=%x\n",u32_t( ntohs(iph->frag_off) ));

            return 0;
        } else {
            if (ptr + 1 >= option_end) {
                mylog(log_debug, "invaild option ptr+1==option_end\n");
                return -1;
            } else {
                int len = (unsigned char)*(ptr + 1);
                if (len <= 1) {
                    mylog(log_debug, "invaild option len %d\n", len);
                    return -1;
                }
                ptr += len;
            }
        }
    }

    return 0;
}
int do_keep_alive(dest_t &dest) {
    if (get_current_time() - last_keep_alive_time > u64_t(keep_alive_interval)) {
        last_keep_alive_time = get_current_time();
        char data[buf_len];
        int len;
        data[0] = header_keep_alive;
        len = 1;

        assert(dest.cook == 1);
        // do_cook(data,len);

        delay_send(0, dest, data, len);
    }
    return 0;
}