Hello

I try to send DHCP RENEW packets to the network and receive the responses. I broadcast the packet and I can see that it's successfully sent using Wireshark. But I have difficulties receiving the responses.I use packet sockets to catch the packets. I can see that there are responses to my RENEW packet using Wireshark, but my function 'packet_receive_renew' sometimes catch the packets but sometimes it can not catch the packets. I set the file descriptor using FDSET but the 'select' in my code can not realize that there are new packets for that file descriptor and timeout occurs. I couldn't make it clear that why it sometimes catches the packets and sometimes doesn't. Anybody have an idea? Thanks in advance.

Here's the receive function.

int packet_receive_renew(struct client_info* info)

{ int fd; struct sockaddr_ll sock, si_other; struct sockaddr_in si_me; fd_set rfds; struct timeval tv; time_t start, end; int bcast = 1;

int ret = 0, try = 0;
char buf[1500] = {'\0'};
uint8_t tmp[BUFLEN] = {'\0'};
struct dhcp_packet pkt;
socklen_t slen = sizeof(si_other);
struct dhcps* new_dhcps;

memset((char *) &si_me, 0, sizeof(si_me));
memset((char *) &si_other, 0, sizeof(si_other));
memset(&pkt, 0, sizeof(struct dhcp_packet));

define SERVER_AND_CLIENT_PORTS ((67 << 16) + 68)

static const struct sock_filter filter_instr[] = {
    /* check for udp */
    BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
    BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 4),     /* L5, L1, is UDP? */
    /* skip IP header */
    BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0),                     /* L5: */
    /* check udp source and destination ports */
    BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0),
    BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */
    /* returns */
    BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ),                   /* L3: pass */
    BPF_STMT(BPF_RET|BPF_K, 0),                             /* L4: reject */
};

static const struct sock_fprog filter_prog = {
    .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
    /* casting const away: */
    .filter = (struct sock_filter *) filter_instr,
};

printf("opening raw socket on ifindex %d\n", info->interf.if_index);

if (-1==(fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))))
{
    perror("packet_receive_renew::socket");
    return -1;
}

printf("got raw socket fd %d\n", fd);

/* Use only if standard ports are in use */
/* Ignoring error (kernel may lack support for this) */
if (-1==setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog, sizeof(filter_prog)))
    perror("packet_receive_renew::setsockopt");

sock.sll_family = AF_PACKET;
sock.sll_protocol = htons(ETH_P_IP);
//sock.sll_pkttype = PACKET_BROADCAST;
sock.sll_ifindex = info->interf.if_index;
if (-1 == bind(fd, (struct sockaddr *) &sock, sizeof(sock))) {
    perror("packet_receive_renew::bind");
    close(fd);
    return -3;
}

if (-1 == setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &bcast, sizeof(bcast))) {
    perror("packet_receive_renew::setsockopt");
    close(fd);
    return -1;
}

FD_ZERO(&rfds);
FD_SET(fd, &rfds);
tv.tv_sec = TIMEOUT;
tv.tv_usec = 0;
ret = time(&start);
if (-1 == ret) {
    perror("packet_receive_renew::time");
    close(fd);
    return -1;
}

while(1) {
    ret = select(fd + 1, &rfds, NULL, NULL, &tv);
    time(&end);
    if (TOTAL_PENDING <= (end - start)) {
        fprintf(stderr, "End receiving\n");
        break;
    }
    if (-1 == ret)
    {
        perror("packet_receive_renew::select");
        close(fd);
        return -4;
    }
    else if (ret) {
        new_dhcps = (struct dhcps*)calloc(1, sizeof(struct dhcps));
        if (-1 == recvfrom(fd, buf, 1500, 0, (struct sockaddr*)&si_other, &slen)) {
            perror("packet_receive_renew::recvfrom");
            close(fd);
            return -4;
        }
        deref_packet((unsigned char*)buf, &pkt, info);
        if (-1!=(ret=get_option_val(pkt.options, DHO_DHCP_SERVER_IDENTIFIER, tmp))) {
            sprintf((char*)tmp, "%d.%d.%d.%d", tmp[0],tmp[1],tmp[2],tmp[3]);
            fprintf(stderr, "Received renew from %s\n", tmp);
        }
        else
        {
            fprintf(stderr, "Couldnt get DHO_DHCP_SERVER_IDENTIFIER%s\n", tmp);
            close(fd);
            return -5;
        }
        new_dhcps->dhcps_addr = strdup((char*)tmp);

        //add to list
        if (info->dhcps_list)
            info->dhcps_list->next = new_dhcps;
        else
            info->dhcps_list = new_dhcps;
        new_dhcps->next = NULL;
    }
    else {
        try++;
        tv.tv_sec = TOTAL_PENDING - try * TIMEOUT;
        tv.tv_usec = 0;
        fprintf(stderr, "Timeout occured\n");
    }
}
close(fd);
printf("close fd:%d\n", fd);
return 0;

}