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server.c
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server.c
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/*
* server.c
*
* This is the main server program which services file transfer requests from
* different clients. For each new client request, a separate child is
* spawned. This uses a protocol library that ensures ordered delivery of
* data.
*
* October 2012
*/
/* Includes */
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <errno.h>
#include <pthread.h>
#include <assert.h>
#include "server.h"
#include "rudp.h"
/* Globals */
server_params_t *serv_params;
/*
* sigchild_handler
*
* This will be called when one of the server-child processes die
*/
static void
sigchild_handler (int signo)
{
int i;
pid_t pid, del_pid = 0;
int stat;
while ((pid = waitpid(-1, &stat, WNOHANG)) > 0) {
printf("\nsigchild received: child %d terminated (%d)\n",
(int)pid, stat);
if (del_pid == 0) {
del_pid = pid;
}
}
/*
* We go the PID of the child who died. Walk through the cli_info
* structure array and purge the entry corresponding to this child. Close
* the associated client socket before purging the entry.
*/
for (i = 0; i < MAX_CLIENTS; i++) {
if (!serv_params->cli_info[i].valid) {
continue;
}
if (serv_params->cli_info[i].pid == (int)del_pid ||
serv_params->cli_info[i].pid == 0) {
printf("sigchild_handler: purging entry corresponding to "
"child %d, client %s (%d)\n", (int)del_pid,
serv_params->cli_info[i].ip,
serv_params->cli_info[i].port);
close(serv_params->cli_info[i].connection_sock);
bzero(&serv_params->cli_info[i], sizeof(cli_info_t));
break;
}
}
}
/*
* init_listening_sockets
*
* Initialize and bind sockets on all the interfaces present on the server.
* Also cache the information on IP, Net mask and Subnet associated with each
* interface in a local array of connection structures.
*/
static int
init_listening_sockets (void)
{
int sockfd, idx = 0, optval = 1;
struct ifi_info *ifi;
struct sockaddr_in *sa, *netmask;
char ip[IP_LEN], mask[IP_LEN], subnet[IP_LEN];
printf("\nINTERFACE LIST:\n");
/* Walk through all the interfaces in the system */
for (ifi = Get_ifi_info(AF_INET, 1); ifi != NULL; ifi = ifi->ifi_next) {
/* Create and bind the socket on this interface */
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));
sa = (struct sockaddr_in *)ifi->ifi_addr;
sa->sin_family = AF_INET;
sa->sin_port = htons(serv_params->port);
netmask = (struct sockaddr_in *)ifi->ifi_ntmaddr;
bind(sockfd, (struct sockaddr *)sa, sizeof(struct sockaddr_in));
/* Store the connection details in our local conn_info structure */
bzero(&serv_params->conn[idx], sizeof(conn_info_t));
serv_params->conn[idx].sock = sockfd;
memcpy(serv_params->conn[idx].ifname, ifi->ifi_name, IFNAME_LEN);
memcpy(&serv_params->conn[idx].ip, sa, sizeof(struct sockaddr_in));
memcpy(&serv_params->conn[idx].netmask, netmask,
sizeof(struct sockaddr_in));
serv_params->conn[idx].subnet.sin_addr.s_addr =
(serv_params->conn[idx].ip.sin_addr.s_addr &
serv_params->conn[idx].netmask.sin_addr.s_addr);
/* Display it! */
printf("interface: %s ip: %s mask: %s subnet: %s\n",
serv_params->conn[idx].ifname,
inet_ntop(AF_INET, &(serv_params->conn[idx].ip.sin_addr),
ip, IP_LEN),
inet_ntop(AF_INET, &(serv_params->conn[idx].netmask.sin_addr),
mask, IP_LEN),
inet_ntop(AF_INET, &(serv_params->conn[idx].subnet.sin_addr),
subnet, IP_LEN));
idx++;
}
serv_params->conn_count = idx;
return 0;
}
/*
* init_connection_socket
*
* Initialize a connection socket that the server will use to communicate with
* a specific client. This is created by the child spawned by the server to
* handle a particular client.
*/
static int
init_connection_socket (char *server_ip, int client_local, cli_info_t *cli_info)
{
int sockfd, ret, optval = 1, buf_size;
struct sockaddr_in cli_addr, serv_addr;
struct sockaddr_in sock_addr;
int sock_len;
char buf[IP_LEN];
/* Create the socket */
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd < 0) {
printf("init_connection_socket: failed to create socket on the "
"client (%d)\n", errno);
return -1;
}
/* Set buffer size */
buf_size = MAX_BUFFER_SIZE;
if (setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &buf_size,
sizeof(buf_size)) < 0) {
printf("init_connection_socket: failed to set recv buf (%d)\n", errno);
return -1;
}
if (setsockopt(sockfd, SOL_SOCKET, SO_SNDBUF, &buf_size,
sizeof(buf_size)) < 0) {
printf("init_connection_socket: failed to set send buf (%d)\n", errno);
return -1;
}
/* Set SO_DONTROUTE if the client is local */
if (client_local) {
if (setsockopt(sockfd, SOL_SOCKET, SO_DONTROUTE,
&optval, sizeof(optval)) < 0) {
printf("init_connection_socket: failed to set SO_DONTROUTE (%d)\n",
errno);
return -1;
}
}
cli_info->connection_sock = sockfd;
/* Bind the socket to the server-ip and an ephemeral port */
bzero(&serv_addr, sizeof(struct sockaddr_in));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(0);
inet_pton(AF_INET, server_ip, &serv_addr.sin_addr);
ret = bind(sockfd, (struct sockaddr *)(&serv_addr),
sizeof(struct sockaddr_in));
if (ret < 0) {
printf("init_connection_socket: bind failed (%d)\n", errno);
return -1;
}
/* Print out the socket information */
sock_len = sizeof(struct sockaddr);
bzero(&sock_addr, sizeof(struct sockaddr_in));
getsockname(sockfd, (struct sockaddr *)&sock_addr, &sock_len);
printf("Connection socket created and bound to %s port %d\n",
inet_ntop(AF_INET, &sock_addr.sin_addr, buf, IP_LEN),
ntohs(sock_addr.sin_port));
cli_info->connection_port = ntohs(sock_addr.sin_port);
/* Connect to the client */
bzero(&cli_addr, sizeof(struct sockaddr_in));
cli_addr.sin_family = AF_INET;
cli_addr.sin_port = htons(cli_info->port);
inet_pton(AF_INET, cli_info->ip, &cli_addr.sin_addr);
ret = connect(sockfd, (struct sockaddr *)&cli_addr,
sizeof(struct sockaddr));
if (ret != 0) {
printf("init_connection_socket: failed to connect to client\n");
return -1;
}
/* Print out the client information */
sock_len = sizeof(struct sockaddr);
bzero(&sock_addr, sizeof(struct sockaddr_in));
getpeername(sockfd, (struct sockaddr *)&sock_addr, &sock_len);
printf("Connection socket connected to client %s port %d\n",
inet_ntop(AF_INET, &sock_addr.sin_addr, buf, IP_LEN),
ntohs(sock_addr.sin_port));
return 0;
}
/*
* check_client_on_same_network
*
* This function checks if the client and server are on the same network.
* Returns -1 upon error. Returns 1 if both are on the same network.
*/
static int
check_client_on_same_network (conn_info_t *server_conn, char *client_ip)
{
in_addr_t client_addr;
bzero(&client_addr, sizeof(struct in_addr));
inet_pton(AF_INET, client_ip, &client_addr);
if ((server_conn->netmask.sin_addr.s_addr & client_addr) ==
(server_conn->subnet.sin_addr.s_addr)) {
return 1;
}
return 0;
}
/*
* send_file_data
*
* This is called once the connection is successfully established with the
* client. It transfers the given file contents to the client.
*/
static void
send_file_data (int client_fd, char *filename)
{
int ret, fd, bytes_read;
char *buf;
/* Sanity check */
if (!filename) {
return;
}
buf = (char *)malloc(FILE_CHUNK_SIZE);
if (!buf) {
printf("send_file_data: memory failure\n");
return;
}
/* Open the file */
fd = open(filename, O_RDONLY);
if (fd < 0) {
printf("\nsend_file_data: failed to open file %s\n", filename);
printf("send_file_data: closing file transfer\n\n");
/* Notify the client */
rudp_send_ctrl_packet(client_fd, MSG_TYPE_ERROR_INVALID_FILE);
return;
}
printf("Starting file transfer\n\n");
/*
* Read the file contents in chunks of 4K and send it across to the
* client.
*/
bzero(buf, FILE_CHUNK_SIZE);
bytes_read = read(fd, buf, FILE_CHUNK_SIZE);
while (bytes_read > 0) {
ret = rudp_send(client_fd, buf, bytes_read);
if (ret < 0) {
printf("send_file_data: failed with error %d\n", errno);
return;
}
/* Read the next chunk from the file */
bzero(buf, FILE_CHUNK_SIZE);
bytes_read = read(fd, buf, FILE_CHUNK_SIZE);
}
/*
* All the file contents have been transferred successfully. Close the
* connection gracefully.
*/
ret = rudp_close(client_fd);
if (ret < 0) {
printf("send_file_data: failed to close the connection (%d)\n", errno);
}
/* All done */
free(buf);
return;
}
/*
* handle_client
*
* Main routine for the server-child. This is invoked whenever a new client
* request is received.
*/
static void
handle_client (int cli_sock, struct sockaddr_in *cli_addr, int cli_idx,
void *buf)
{
char client_ip[IP_LEN], server_ip[IP_LEN], send_buf[MAXLINE];
int i, client_port, server_port, is_local, ret;
conn_info_t *conn;
cli_info_t *cli_info = &serv_params->cli_info[cli_idx];
inet_ntop(AF_INET, &(cli_addr->sin_addr), client_ip, IP_LEN);
client_port = ntohs(cli_addr->sin_port);
/*
* Close all the sockets inherited from the parent except for the socket
* on which the connection was received.
*/
for (i = 0; i < serv_params->conn_count; i++) {
if (serv_params->conn[i].sock == cli_sock) {
conn = &serv_params->conn[i];
continue;
}
close(serv_params->conn[i].sock);
}
/*
* Check whether the client and server are on the same host / network. If
* so, we have to set the MSG_DONTROUTE flag.
*/
is_local = 0;
inet_ntop(AF_INET, &(conn->ip.sin_addr), server_ip, IP_LEN);
server_port = serv_params->port;
if (strncmp(server_ip, LOCALHOST_IP, IP_LEN) == 0) {
is_local = 1;
printf("Server and Client are on the same host\n");
} else {
is_local = check_client_on_same_network(conn, client_ip);
if (is_local) {
printf("Server and Client are on the same network (Local)\n");
} else {
printf("Server and Client are on different networks (Non-Local)\n");
}
}
printf("Selected Server: %s (%d)\n", server_ip, server_port);
printf("Selected Client: %s (%d)\n\n", client_ip, client_port);
printf("Filename received from client for transfer: %s\n\n", (char *)buf);
/* Create a new connection socket to communicate with the client */
ret = init_connection_socket(server_ip, is_local, cli_info);
if (ret != 0) {
printf("handle_client: failed to initialize connection socket\n");
return;
}
/* Send the port associated with the connection socket to the client */
sprintf(send_buf, "%d", cli_info->connection_port);
ret = rudp_srv_conn_send(conn->sock, cli_info->connection_sock, cli_addr,
(void *)send_buf, MAXLINE);
if (ret < 0) {
printf("handle_client: failed to send connection socket port to "
"client\n");
return;
}
printf("Connection re-established with the client\n");
/* Now send the file contents to the client */
send_file_data(cli_info->connection_sock, buf);
/* All done */
exit(0);
}
/*
* is_new_client_request
*
* This checks whether the given client is connecting with us for the first
* time or if it's a duplicate request. If it's a new request, we cache the
* request. We get duplicate requests when the connection port information we
* sent to the client is lost.
*/
static int
is_new_client_request (struct sockaddr_in *cli_addr, int *cli_idx)
{
char cli_ip[IP_LEN];
int i, idx, cli_port;
inet_ntop(AF_INET, &(cli_addr->sin_addr), cli_ip, IP_LEN);
cli_port = ntohs(cli_addr->sin_port);
idx = MAX_CLIENTS;
for (i = 0; i < MAX_CLIENTS; i++) {
/* Skip if the entry is invalid */
if (!serv_params->cli_info[i].valid) {
if (idx == MAX_CLIENTS) {
idx = i;
}
continue;
}
/* Check if it's a duplicate request */
if (strncmp(serv_params->cli_info[i].ip, cli_ip, IP_LEN) == 0 &&
serv_params->cli_info[i].port == cli_port) {
printf("is_new_client_request: duplicate client request %s(%d). "
"ignoring\n", cli_ip, cli_port);
return 0;
}
}
if (idx == MAX_CLIENTS) {
printf("cannot process new request as number of clients exceed "
"maximum\n");
return 0;
}
/* Cache the request. PID will be updated after forking the child. */
strncpy(serv_params->cli_info[idx].ip, cli_ip, IP_LEN);
serv_params->cli_info[idx].port = cli_port;
serv_params->cli_info[idx].valid = 1;
*cli_idx = idx;
serv_params->cli_count += 1;
printf("Received new connection request from client %s (%d)\n\n",
cli_ip, cli_port);
return 1;
}
/*
* conn_listen
*
* This is the main loop for the server wherein it listens for incoming
* connections using select.
*/
static void
conn_listen (void)
{
int i, max_fd, bytes_read, ret, pid, cli_idx;
fd_set fdset, origset;
char buf[10000];
struct sockaddr_in cli_addr;
int len = sizeof(struct sockaddr);
printf("\nWaiting for incoming connections...\n");
/* Setup parameters for the select call and invoke it */
FD_ZERO(&fdset);
max_fd = -1;
for (i = 0; i < serv_params->conn_count; i++) {
FD_SET(serv_params->conn[i].sock, &fdset);
if (serv_params->conn[i].sock > max_fd) {
max_fd = serv_params->conn[i].sock;
}
}
origset = fdset;
/* Main Loop */
while (1) {
fdset = origset;
ret = select(max_fd + 1, &fdset, NULL, NULL, NULL);
if (ret < 0) {
if (errno == EINTR) {
continue;
} else {
/* Should never happen! */
assert(0);
}
}
/* See which socket the request arrived on and read from it */
for (i = 0; i < serv_params->conn_count; i++) {
if (FD_ISSET(serv_params->conn[i].sock, &fdset)) {
/* See who we got the message from */
bzero(&cli_addr, sizeof(struct sockaddr_in));
bytes_read = rudp_srv_conn_recv(serv_params->conn[i].sock,
buf, sizeof(buf),
(struct sockaddr *)&cli_addr,
&len);
/*
* Check if we have already received a message from this guy.
* If so, we need to ignore the message. If it's a new
* request, then cache it to avoid duplicates later on.
*/
ret = is_new_client_request(&cli_addr, &cli_idx);
if (ret) {
/* It's a new request. Spawn a child to handle it */
pid = fork();
if (pid == 0) {
/* Call the child routine to handle this request */
handle_client(serv_params->conn[i].sock, &cli_addr,
cli_idx, buf);
} else {
/* Store the child's PID in our table */
serv_params->cli_info[cli_idx].pid = pid;
}
}
}
}
}
}
/*
* read_server_params
*
* Read the input parameters for the server from the file server.in
*/
static int
read_server_params (rudp_srv_state_t *rudp_srv_state)
{
int fd, val, lineno = 1;
char buf[MAXLINE];
/* Open the input file */
fd = open(SERVER_INPUT, O_RDONLY);
if (!fd) {
return -1;
}
/* Read the parameters one line at a time */
bzero(serv_params, sizeof(server_params_t));
bzero(rudp_srv_state, sizeof(rudp_srv_state_t));
bzero(buf, MAXLINE);
while (readline(fd, buf, MAXLINE)) {
val = atoi(buf);
if (val == 0) {
return -1;
}
if (lineno == 1) {
serv_params->port = val;
} else if (lineno == 2) {
rudp_srv_state->max_cwnd_size = val;
}
lineno++;
bzero(buf, MAXLINE);
}
printf("\nSERVER PARAMS:\n");
printf("port: %d\n", serv_params->port);
printf("sending window size: %d\n", rudp_srv_state->max_cwnd_size);
return 0;
}
/* Main entry point */
int
main (int argc, char *argv[])
{
int ret;
rudp_srv_state_t rudp_srv_state;
/* Sanity check */
if (argc != 1) {
printf("usage: ./server\n");
return -1;
}
/* Register for SIGCHLD */
signal(SIGCHLD, sigchild_handler);
/* Initialize the structure for holding server parameters */
serv_params = (server_params_t *)malloc(sizeof(server_params_t));
if (!serv_params) {
printf("main: failed to initialize server parameters\n");
return -1;
}
/* Read the server parameters from server.in */
ret = read_server_params(&rudp_srv_state);
if (ret != 0) {
printf("main: failed to read server parameters from server.in\n");
return -1;
}
/* Initialize the RUDP library */
ret = rudp_srv_init(&rudp_srv_state);
if (ret != 0) {
printf("main: failed to initialize the RUDP library\n");
return -1;
}
/* Setup connections on all the interfaces */
init_listening_sockets();
/* Monitor the created sockets using select */
conn_listen();
return 0;
}
/* End of File */