dhcp-inform for sip server ( = get p-cscf server for ims)

gistfile1.txt

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/udp.h>
#include <ifaddrs.h>
#include <net/if.h>

#define DHCPV6_CLIENT_PORT 546
#define DHCPV6_SERVER_PORT 547
#define DHCPV6_MULTICAST_GROUP "FF02::1:2"
#define DHCPV6_INFORMATION_REQUEST 11
#define DHCPV6_DNS_SERVERS 23
#define DHCPV6_DOMAIN_LIST 24
#define SIP_SERVER_D 21
#define SIP_SERVER_A 22
#define OPTION_REQUEST_OPTION 6

// Function to create a DHCPv6 Information Request packet
int create_dhcpv6_info_request(unsigned char *packet) {
    // DHCPv6 Message Type (Information Request)
    int i = 0;
    packet[i++] = 1;//solicit 11; // information request

    // Transaction ID (random 3 bytes)
    packet[i++] = rand();
    packet[i++] = rand();
    packet[i++] = rand();

    // Options
    // Option: DNS Servers (23)
#if 0
    packet[i++] = (DHCPV6_DNS_SERVERS >> 8) & 0xFF;
    packet[i++] = DHCPV6_DNS_SERVERS & 0xFF;
    packet[i++] = 0x00; // Length (0 for now, will be filled later)
    packet[i++] = 0x00;

    // Option: Domain List (24)
    packet[i++] = (DHCPV6_DOMAIN_LIST >> 8) & 0xFF;
    packet[i++] = DHCPV6_DOMAIN_LIST & 0xFF;
    packet[i++] = 0x00; // Length (0 for now, will be filled later)
    packet[i++] = 0x00;

    packet[i++] = (SIP_SERVER_A >> 8) & 0xFF;
    packet[i++] = SIP_SERVER_A & 0xFF;
    packet[i++] = 0x00; // Length (0 for now, will be filled later)
    packet[i++] = 0x00;

    // Option: Domain List (24)
    packet[i++] = (SIP_SERVER_D >> 8) & 0xFF;
    packet[i++] = SIP_SERVER_D & 0xFF;
    packet[i++] = 0x00; // Length (0 for now, will be filled later)
    packet[i++] = 0x00;
#endif
    packet[i++] = (OPTION_REQUEST_OPTION >> 8) & 0xFF;
    packet[i++] = OPTION_REQUEST_OPTION & 0xFF;
    packet[i++] = 0;
    packet[i++] = 8;

    packet[i++] = (DHCPV6_DNS_SERVERS >> 8) & 0xFF;
    packet[i++] = DHCPV6_DNS_SERVERS & 0xFF;
    packet[i++] = (DHCPV6_DOMAIN_LIST >> 8) & 0xFF;
    packet[i++] = DHCPV6_DOMAIN_LIST & 0xFF;
    packet[i++] = (SIP_SERVER_D >> 8) & 0xFF;
    packet[i++] = SIP_SERVER_D & 0xFF;
    packet[i++] = (SIP_SERVER_A >> 8) & 0xFF;
    packet[i++] = SIP_SERVER_A & 0xFF;

    // Option: End (255)
    packet[i++] = 0xFF;
    return i;
}

// Function to get the interface index by name
int get_interface_index(const char *ifname) {
    struct ifaddrs *ifaddr, *ifa;
    int ifindex = -1;

    if (getifaddrs(&ifaddr) == -1) {
        perror("getifaddrs");
        exit(EXIT_FAILURE);
    }

    for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
        if (ifa->ifa_addr == NULL)
            continue;
        if (strcmp(ifa->ifa_name, ifname) == 0) {
            ifindex = if_nametoindex(ifa->ifa_name);
            break;
        }
    }

    freeifaddrs(ifaddr);
    return ifindex;
}

// Function to send the DHCPv6 Information Request packet
void send_dhcpv6_info_request(const char *ifname) {
    int sockfd;
    struct sockaddr_in6 server_addr;
    unsigned char packet[1024];
    int packet_len;
    int ifindex;

    // Create a raw socket
    sockfd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
    if (sockfd < 0) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // Set the interface index for sending multicast packets
    ifindex = get_interface_index(ifname);
    if (ifindex == -1) {
        perror("get_interface_index");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_MULTICAST_IF, &ifindex, sizeof(ifindex)) < 0) {
        perror("setsockopt");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    struct sockaddr_in6 serv_addr;
    socklen_t addrlen = sizeof(serv_addr);
    // Prepare the sockaddr_in6 structure
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin6_family = AF_INET6;
    serv_addr.sin6_addr = in6addr_any; // Bind to all available IPv6 addresses
    serv_addr.sin6_port = htons(546);  // DHCPv6 client port

    // Bind the socket to the DHCPv6 client port
    if (bind(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
        perror("Bind failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }


    // Set up the server address
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin6_family = AF_INET6;
    server_addr.sin6_port = htons(DHCPV6_SERVER_PORT);
    inet_pton(AF_INET6, DHCPV6_MULTICAST_GROUP, &server_addr.sin6_addr);

    // Create the DHCPv6 Information Request packet
    packet_len = create_dhcpv6_info_request(packet);

    // Send the packet
    if (sendto(sockfd, packet, packet_len, 0, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("sendto");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    printf("DHCPv6 Information Request sent successfully on interface %s.\n", ifname);

    // Close the socket
    close(sockfd);
}

int main(int argc, char *argv[]) {
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <interface>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    const char *ifname = argv[1];
    send_dhcpv6_info_request(ifname);
    return 0;
}