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Software Vault: The Gold Collection
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Software Vault - The Gold Collection (American Databankers) (1993).ISO
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netprog.zip
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NETPROG.TAR
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tftp
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netudp.c
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C/C++ Source or Header
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1989-12-17
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12KB
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468 lines
/*
* TFTP network handling for UDP/IP connection.
*/
#include "netdefs.h"
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
extern int errno;
#ifndef CLIENT
#ifndef SERVER
either CLIENT or SERVER must be defined
#endif
#endif
int sockfd = -1; /* fd for socket of server */
char openhost[MAXHOSTNAMELEN] = { 0 }; /* remember host's name */
extern int traceflag; /* TFTP variable */
#ifdef CLIENT
extern struct sockaddr_in udp_srv_addr; /* set by udp_open() */
extern struct servent udp_serv_info; /* set by udp_open() */
static int recv_first;
/*
* Open the network connection.
*/
int
net_open(host, service, port)
char *host; /* name of other system to communicate with */
char *service; /* name of service being requested */
int port; /* if > 0, use as port#, else use value for service */
{
struct sockaddr_in addr;
/*
* Call udp_open() to create the socket. We tell udp_open to
* not connect the socket, since we'll receive the first response
* from a port that's different from where we send our first
* datagram to.
*/
if ( (sockfd = udp_open(host, service, port, 1)) < 0)
return(-1);
DEBUG2("net_open: host %s, port# %d",
inet_ntoa(udp_srv_addr.sin_addr),
ntohs(udp_srv_addr.sin_port));
strcpy(openhost, host); /* save the host's name */
recv_first = 1; /* flag for net_recv() */
return(0);
}
/*
* Close the network connection.
*/
net_close()
{
DEBUG2("net_close: host = %s, fd = %d", openhost, sockfd);
close(sockfd);
sockfd = -1;
}
/*
* Send a record to the other end.
* We use the sendto() system call, instead of send(), since the address
* of the server changes after the first packet is sent.
*/
net_send(buff, len)
char *buff;
int len;
{
register int rc;
DEBUG3("net_send: sent %d bytes to host %s, port# %d",
len, inet_ntoa(udp_srv_addr.sin_addr),
ntohs(udp_srv_addr.sin_port));
rc = sendto(sockfd, buff, len, 0, (struct sockaddr *) &udp_srv_addr,
sizeof(udp_srv_addr));
if (rc < 0)
err_dump("send error");
}
/*
* Receive a record from the other end.
*/
int /* return #bytes in packet, or -1 on EINTR */
net_recv(buff, maxlen)
char *buff;
int maxlen;
{
register int nbytes;
int fromlen; /* value-result parameter */
struct sockaddr_in from_addr; /* actual addr of sender */
fromlen = sizeof(from_addr);
nbytes = recvfrom(sockfd, buff, maxlen, 0,
(struct sockaddr *) &from_addr, &fromlen);
/*
* The recvfrom() system call can be interrupted by an alarm
* interrupt, in case it times out. We just return -1 if the
* system call was interrupted, and the caller must determine
* if this is OK or not.
*/
if (nbytes < 0) {
if (errno == EINTR)
return(-1);
else
err_dump("recvfrom error");
}
DEBUG3("net_recv: got %d bytes from host %s, port# %d",
nbytes, inet_ntoa(from_addr.sin_addr),
ntohs(from_addr.sin_port));
/*
* The TFTP client using UDP/IP has a funny requirement.
* The problem is that UDP is being used for a
* "connection-oriented" protocol, which it wasn't really
* designed for. Rather than tying up a single well-known
* port number, the server changes its port after receiving
* the first packet from a client.
*
* The first packet a client sends to the server (an RRQ or a WRQ)
* must be sent to its well-known port number (69 for TFTP).
* The server is then to choose some other port number for all
* subsequent transfers. The recvfrom() call above will return
* the server's current address. If the port number that we
* sent the last packet to (udp_srv_addr.sin_port) is still equal to
* the initial well-known port number (udp_serv_info.s_port), then we
* must set the server's port for our next transmission to be
* the port number from the recvfrom(). See Section 4 of the RFC
* where it talks about the TID (= port#).
*
* Furthermore, after we have determined the port number that
* we'll be receiving from, we can verify each datagram to make
* certain its from the right place.
*/
if (recv_first) {
/*
* This is the first received message.
* The server's port should have changed.
*/
if (udp_srv_addr.sin_port == from_addr.sin_port)
err_dump("first receive from port %d",
ntohs(from_addr.sin_port));
udp_srv_addr.sin_port = from_addr.sin_port;
/* save the new port# of the server */
recv_first = 0;
} else if (udp_srv_addr.sin_port != from_addr.sin_port) {
err_dump("received from port %d, expected from port %d",
ntohs(from_addr.sin_port),
ntohs(udp_srv_addr.sin_port));
}
return(nbytes); /* return the actual length of the message */
}
#endif /* CLIENT */
#ifdef SERVER
#include <sys/ioctl.h>
struct sockaddr_in udp_srv_addr; /* server's Internet socket addr */
struct sockaddr_in udp_cli_addr; /* client's Internet socket addr */
struct servent udp_serv_info; /* from getservbyname() */
static int recv_nbytes = -1;
static int recv_first = 0;
extern char recvbuff[]; /* this is declared in initvars.c */
/*
* Initialize the network connection for the server, when it has *not*
* been invoked by inetd.
*/
net_init(service, port)
char *service; /* the name of the service we provide */
int port; /* if nonzero, this is the port to listen on;
overrides the standard port for the service */
{
struct servent *sp;
/*
* We weren't started by a master daemon.
* We have to create a socket ourselves and bind our well-known
* address to it.
*/
if ( (sp = getservbyname(service, "udp")) == NULL)
err_dump("net_init: unknown service: %s/udp", service);
if (port > 0)
sp->s_port = htons(port); /* caller's value */
udp_serv_info = *sp; /* structure copy */
if ( (sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
err_dump("net_init: can't create datagram socket");
/*
* Bind our local address so that any client can send to us.
*/
bzero((char *) &udp_srv_addr, sizeof(udp_srv_addr));
udp_srv_addr.sin_family = AF_INET;
udp_srv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
udp_srv_addr.sin_port = sp->s_port;
if (bind(sockfd, (struct sockaddr *) &udp_srv_addr,
sizeof(udp_srv_addr)) < 0)
err_dump("net_init: can't bind local address");
}
/*
* Initiate the server's end.
* We are passed a flag that says whether or not we were started
* by a "master daemon," such as the inetd program under 4.3BSD.
* A master daemon will have already waited for a message to arrive
* for us, and will have already set up the connection to the client.
* If we weren't started by a master daemon, then we must wait for a
* client's request to arrive.
*/
int
net_open(inetdflag)
int inetdflag; /* true if inetd started us */
{
register int childpid, nbytes;
int on;
on = 1;
if (inetdflag) {
#ifdef BSD /* assumes 4.3BSD inetd */
/*
* When we're fired up by inetd under 4.3BSD, file
* descriptors 0, 1 and 2 are sockets to the client.
* We want to first receive the message that's waiting
* for us on the socket, and then close the socket.
* This will let inetd go back to waiting for another
* request on our "well-known port."
*/
sockfd = 0; /* descriptor for net_recv() to recvfrom() */
/*
* Set the socket to nonblocking, since inetd won't invoke
* us unless there's a datagram ready for us to read.
*/
if (ioctl(sockfd, FIONBIO, (char *) &on) < 0)
err_dump("ioctl FIONBIO error");
#endif /* BSD inetd specifics */
}
/*
* Now read the first message from the client.
* In the inetd case, the message is already here and the call to
* net_recv() returns immediately. In the other case, net_recv()
* blocks until a client request arrives.
*/
recv_first = 1; /* tell net_recv to save the address */
recv_nbytes = -1; /* tell net_recv to do the actual read */
nbytes = net_recv(recvbuff, MAXBUFF);
/*
* Fork a child process to handle the client's request.
* In the inetd case, the parent exits, which allows inetd to
* handle the next request that arrives to this well-known port
* (inetd's wait mode for a datagram socket).
* Otherwise the parent returns the child pid to the caller, which
* is probably a concurrent server that'll call us again, to wait
* for the next client request to this well-known port.
*/
if ( (childpid = fork()) < 0)
err_dump("server can't fork");
else if (childpid > 0) { /* parent */
if (inetdflag)
exit(0); /* inetd case; we're done */
else
return(childpid); /* independent server */
}
/*
* Child process continues here.
* First close the socket that is bound to the well-known address:
* the parent will handle any further requests that arrive there.
* We've already read the message that arrived for us to handle.
*/
if (inetdflag) {
close(0);
close(1);
close(2);
} else {
close(sockfd);
}
errno = 0; /* in case it was set by a close() */
/*
* Create a new socket.
* Bind any local port# to the socket as our local address.
* We don't connect(), since net_send() uses the sendto()
* system call, specifying the destination address each time.
*/
if ( (sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
err_dump("net_open: can't create socket");
bzero((char *) &udp_srv_addr, sizeof(udp_srv_addr));
udp_srv_addr.sin_family = AF_INET;
udp_srv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
udp_srv_addr.sin_port = htons(0);
if (bind(sockfd, (char *) &udp_srv_addr, sizeof(udp_srv_addr)) < 0)
err_dump("net_open: bind error");
/*
* Now we'll set a special flag for net_recv(), so that
* the next time it's called, it'll know that the recvbuff[]
* already has the received packet in it (from our call to
* net_recv() above).
*/
recv_nbytes = nbytes;
return(0);
}
/*
* Close a socket.
*/
net_close()
{
DEBUG2("net_close: host = %s, fd = %d", openhost, sockfd);
close(sockfd);
sockfd = -1;
}
/*
* Send a record to the other end.
* The "struct sockaddr_in cli_addr" specifies the client's address.
*/
net_send(buff, len)
char *buff;
int len;
{
register int rc;
DEBUG3("net_send: sent %d bytes to host %s, port# %d",
len, inet_ntoa(udp_cli_addr.sin_addr),
ntohs(udp_cli_addr.sin_port));
rc = sendto(sockfd, buff, len, 0, (struct sockaddr *) &udp_cli_addr,
sizeof(udp_cli_addr));
if (rc != len)
err_dump("sendto error");
}
/*
* Receive a record from the other end.
* We're called not only by the user, but also by net_open() above,
* to read the first datagram after a "connection" is established.
*/
int
net_recv(buff, maxlen)
char *buff;
int maxlen;
{
register int nbytes;
int fromlen; /* value-result parameter */
extern int tout_flag; /* set by SIGALRM */
struct sockaddr_in from_addr;
if (recv_nbytes >= 0) {
/*
* First message has been handled specially by net_open().
* It's already been read into recvbuff[].
*/
nbytes = recv_nbytes;
recv_nbytes = -1;
return(nbytes);
}
again:
fromlen = sizeof(from_addr);
nbytes = recvfrom(sockfd, buff, maxlen, 0,
(struct sockaddr *) &from_addr, &fromlen);
/*
* The server can have its recvfrom() interrupted by either an
* alarm timeout or by a SIGCLD interrupt. If it's a timeout,
* "tout_flag" will be set and we have to return to the caller
* to let them determine if another receive should be initiated.
* For a SIGCLD signal, we can restart the recvfrom() ourself.
*/
if (nbytes < 0) {
if (errno == EINTR) {
if (tout_flag)
return(-1);
errno = 0; /* assume SIGCLD */
goto again;
}
err_dump("recvfrom error");
}
DEBUG3("net_recv: got %d bytes from host %s, port# %d",
nbytes, inet_ntoa(from_addr.sin_addr),
ntohs(from_addr.sin_port));
/*
* If "recv_first" is set, then we must save the received
* address that recvfrom() stored in "from_addr" in the
* global "udp_cli_addr".
*/
if (recv_first) {
bcopy((char *) &from_addr, (char *) &udp_cli_addr,
sizeof(from_addr));
recv_first = 0;
}
/*
* Make sure the message is from the expected client.
*/
if (udp_cli_addr.sin_port != 0 &&
udp_cli_addr.sin_port != from_addr.sin_port)
err_dump("received from port %d, expected from port %d",
ntohs(from_addr.sin_port), ntohs(udp_cli_addr.sin_port));
return(nbytes); /* return the actual length of the message */
}
#endif /* SERVER */