comm.c

/*
 * =====================================================================================
 *
 *       Filename:  comm.c
 *
 *    Description:  This file contains the routines to implement the communication between nodes
 *
 *        Version:  1.0
 *        Created:  Thursday 19 September 2019 10:31:35  IST
 *       Revision:  1.0
 *       Compiler:  gcc
 *
 *         Author:  Er. Abhishek Sagar, Networking Developer (AS), sachinites@gmail.com
 *        Company:  Brocade Communications(Jul 2012- Mar 2016), Current : Juniper Networks(Apr 2017 - Present)
 *        
 *        This file is part of the NetworkGraph distribution (https://github.com/sachinites).
 *        Copyright (c) 2017 Abhishek Sagar.
 *        This program is free software: you can redistribute it and/or modify
 *        it under the terms of the GNU General Public License as published by  
 *        the Free Software Foundation, version 3.
 *
 *        This program is distributed in the hope that it will be useful, but 
 *        WITHOUT ANY WARRANTY; without even the implied warranty of 
 *        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
 *        General Public License for more details.
 *
 *        You should have received a copy of the GNU General Public License 
 *        along with this program. If not, see <http://www.gnu.org/licenses/>.
 *
 * =====================================================================================
 */

#include "comm.h"
#include "graph.h"
#include <sys/socket.h>
#include <pthread.h>
#include <netinet/in.h>
#include <memory.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <netdb.h> /*for struct hostent*/
#include "net.h"
#include <unistd.h> // for close

static int
_send_pkt_out(int sock_fd, char *pkt_data, unsigned int pkt_size, 
                unsigned int dst_udp_port_no){

    int rc;
    struct sockaddr_in dest_addr;
   
    struct hostent *host = (struct hostent *) gethostbyname("127.0.0.1"); 
    dest_addr.sin_family = AF_INET;
    dest_addr.sin_port = dst_udp_port_no;
    dest_addr.sin_addr = *((struct in_addr *)host->h_addr);

    rc = sendto(sock_fd, pkt_data, pkt_size, 0, 
            (struct sockaddr *)&dest_addr, sizeof(struct sockaddr));
    
    return rc;
}


static unsigned int udp_port_number = 40000;

static unsigned int 
get_next_udp_port_number(){
    
    return udp_port_number++;
}

void
init_udp_socket(node_t *node){

    if(node->udp_port_number)
        return;
    
    node->udp_port_number = get_next_udp_port_number();
     
    int udp_sock_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP );
    
    if(udp_sock_fd == -1){
        printf("Socket Creation Failed for node %s\n", node->node_name);
        return;   
    }

    struct sockaddr_in node_addr;
    node_addr.sin_family      = AF_INET;
    node_addr.sin_port        = node->udp_port_number;
    node_addr.sin_addr.s_addr = INADDR_ANY;
    if (bind(udp_sock_fd, (struct sockaddr *)&node_addr, sizeof(struct sockaddr)) == -1) {
        printf("Error : socket bind failed for Node %s\n", node->node_name);
        return;
    }

    node->udp_sock_fd = udp_sock_fd;
}

static char recv_buffer[MAX_PACKET_BUFFER_SIZE];
static char send_buffer[MAX_PACKET_BUFFER_SIZE];

static void
_pkt_receive(node_t *receving_node, 
            char *pkt_with_aux_data, 
            unsigned int pkt_size){

    char *recv_intf_name = pkt_with_aux_data;
    interface_t *recv_intf = get_node_if_by_name(receving_node, recv_intf_name);

    if(!recv_intf){
        printf("Error : Pkt recvd on unknown interface %s on node %s\n", 
                    recv_intf->if_name, receving_node->node_name);
        return;
    }

    pkt_receive(receving_node, recv_intf, pkt_with_aux_data + IF_NAME_SIZE, 
                pkt_size - IF_NAME_SIZE);
}

static void *
_network_start_pkt_receiver_thread(void *arg){

    node_t *node;
    glthread_t *curr;
    
    fd_set active_sock_fd_set,
           backup_sock_fd_set;
    
    int sock_max_fd = 0;
    int bytes_recvd = 0;
    
    graph_t *topo = (void *)arg;

    int addr_len = sizeof(struct sockaddr);

    FD_ZERO(&active_sock_fd_set);
    FD_ZERO(&backup_sock_fd_set);
    
    struct sockaddr_in sender_addr;

    ITERATE_GLTHREAD_BEGIN(&topo->node_list, curr){

        node = graph_glue_to_node(curr);
        
        if(!node->udp_sock_fd) 
            continue;

        if(node->udp_sock_fd > sock_max_fd)
            sock_max_fd = node->udp_sock_fd;

        FD_SET(node->udp_sock_fd, &backup_sock_fd_set);
            
    } ITERATE_GLTHREAD_END(&topo->node_list, curr);

    while(1){

        memcpy(&active_sock_fd_set, &backup_sock_fd_set, sizeof(fd_set));

        select(sock_max_fd + 1, &active_sock_fd_set, NULL, NULL, NULL);

        ITERATE_GLTHREAD_BEGIN(&topo->node_list, curr){

            node = graph_glue_to_node(curr);

            if(FD_ISSET(node->udp_sock_fd, &active_sock_fd_set)){
    
                memset(recv_buffer, 0, MAX_PACKET_BUFFER_SIZE);
                bytes_recvd = recvfrom(node->udp_sock_fd, (char *)recv_buffer, 
                        MAX_PACKET_BUFFER_SIZE, 0, (struct sockaddr *)&sender_addr, &addr_len);
                
                _pkt_receive(node, recv_buffer, bytes_recvd);
            }
            
        } ITERATE_GLTHREAD_END(&topo->node_list, curr);
    }
}


void
network_start_pkt_receiver_thread(graph_t *topo){

    pthread_attr_t attr;
    pthread_t recv_pkt_thread;

    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

    pthread_create(&recv_pkt_thread, &attr, 
                    _network_start_pkt_receiver_thread, 
                    (void *)topo);
}

int
send_pkt_to_self(char *pkt, unsigned int pkt_size,
                interface_t *interface){

    int rc = 0;    
    node_t *sending_node = interface->att_node;
    node_t *nbr_node = sending_node;
    
    unsigned int dst_udp_port_no = nbr_node->udp_port_number;
    
    int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP );

    if(sock < 0){
        printf("Error : Sending socket Creation failed , errno = %d", errno);
        return -1;
    }
    
    interface_t *other_interface =  interface;

    memset(send_buffer, 0, MAX_PACKET_BUFFER_SIZE);

    char *pkt_with_aux_data = send_buffer;

    strncpy(pkt_with_aux_data, other_interface->if_name, IF_NAME_SIZE);

    pkt_with_aux_data[IF_NAME_SIZE - 1] = '\0';

    memcpy(pkt_with_aux_data + IF_NAME_SIZE, pkt, pkt_size);

    rc = _send_pkt_out(sock, pkt_with_aux_data, pkt_size + IF_NAME_SIZE, 
                        dst_udp_port_no);

    close(sock);
    return rc; 
       
}

/*Public APIs to be used by the other modules*/
int
send_pkt_out(char *pkt, unsigned int pkt_size, 
             interface_t *interface){

    int rc = 0;

    node_t *sending_node = interface->att_node;
    node_t *nbr_node = get_nbr_node(interface);
    
    if(!nbr_node)
        return -1;

    if(pkt_size + IF_NAME_SIZE > MAX_PACKET_BUFFER_SIZE){
        printf("Error : Node :%s, Pkt Size exceeded\n", sending_node->node_name);
        return -1;
    }

    unsigned int dst_udp_port_no = nbr_node->udp_port_number;
    
    int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP );

    if(sock < 0){
        printf("Error : Sending socket Creation failed , errno = %d", errno);
        return -1;
    }
    
    interface_t *other_interface = &interface->link->intf1 == interface ? \
                                    &interface->link->intf2 : &interface->link->intf1;

    memset(send_buffer, 0, MAX_PACKET_BUFFER_SIZE);

    char *pkt_with_aux_data = send_buffer;

    strncpy(pkt_with_aux_data, other_interface->if_name, IF_NAME_SIZE);

    pkt_with_aux_data[IF_NAME_SIZE - 1] = '\0';

    memcpy(pkt_with_aux_data + IF_NAME_SIZE, pkt, pkt_size);

    rc = _send_pkt_out(sock, pkt_with_aux_data, pkt_size + IF_NAME_SIZE, 
                        dst_udp_port_no);

    close(sock);
    return rc; 
}

extern void
layer2_frame_recv(node_t *node, interface_t *interface,
                     char *pkt, unsigned int pkt_size);

int
pkt_receive(node_t *node, interface_t *interface,
            char *pkt, unsigned int pkt_size){

    /*Make room in the packet buffer by shifting the data towards
      right so that tcp/ip stack can append more hdrs to the packet 
      as required */
    pkt = pkt_buffer_shift_right(pkt, pkt_size, 
            MAX_PACKET_BUFFER_SIZE - IF_NAME_SIZE);

    /*Do further processing of the pkt here*/
    layer2_frame_recv(node, interface, pkt, pkt_size );
    return 0;
}

int
send_pkt_flood(node_t *node, interface_t *exempted_intf, 
                char *pkt, unsigned int pkt_size){

    unsigned int i = 0;
    interface_t *intf; 

    for( ; i < MAX_INTF_PER_NODE; i++){

        intf = node->intf[i];
        if(!intf) return 0;

        if(intf == exempted_intf)
            continue;

        send_pkt_out(pkt, pkt_size, intf);
    }
    return 0;
}

int
send_pkt_flood_l2_intf_only(node_t *node,
                            interface_t *exempted_intf,
                            char *pkt, unsigned int pkt_size){

    unsigned int i = 0;
    interface_t *intf;

    for( ; i < MAX_INTF_PER_NODE; i++){

        intf = node->intf[i];
        if(!intf) return 0;

        if(intf == exempted_intf || 
            !IF_L2_MODE(intf))
            continue;

        send_pkt_out(pkt, pkt_size, intf);
    }
}