minix/commands/simple/tcpd.c
2005-04-21 14:53:53 +00:00

303 lines
6.4 KiB
C
Executable file

/*
tcpd.c
*/
#include <sys/types.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <minix/config.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <net/hton.h>
#include <net/netlib.h>
#include <net/gen/in.h>
#include <net/gen/inet.h>
#include <net/gen/netdb.h>
#include <net/gen/tcp.h>
#include <net/gen/tcp_io.h>
/* This program can be compiled to be paranoid, i.e. check incoming connection
* according to an access file, or to trust anyone. The much smaller "trust
* 'em" binary will call the paranoid version if the access file exists.
*/
static char *arg0, *service;
static unsigned nchildren;
static void report(const char *label)
{
int err= errno;
fprintf(stderr, "%s %s: %s: %s\n", arg0, service, label, strerror(err));
errno= err;
}
static void sigchld(int sig)
{
while (waitpid(0, NULL, WNOHANG) > 0) {
if (nchildren > 0) nchildren--;
}
}
static void release(int *fd)
{
if (*fd != -1) {
close(*fd);
*fd= -1;
}
}
static void usage(void)
{
fprintf(stderr,
"Usage: %s [-d] [-m maxclients] service program [arg ...]\n",
arg0);
exit(1);
}
int main(int argc, char **argv)
{
tcpport_t port;
struct nwio_tcpcl tcplistenopt;
struct nwio_tcpconf tcpconf;
struct nwio_tcpopt tcpopt;
char *tcp_device;
struct servent *servent;
int tcp_fd, client_fd, count, r;
int pfd[2];
unsigned stall= 0;
struct sigaction sa;
sigset_t chldmask, chldunmask, oldmask;
char **progv;
#if !PARANOID
# define debug 0
# define max_children ((unsigned) -1)
arg0= argv[0];
/* Switch to the paranoid version of me if there are flags, or if
* there is an access file.
*/
if (argv[1][0] == '-' || access(_PATH_SERVACCES, F_OK) == 0) {
execv("/usr/bin/tcpdp", argv);
report("tcpdp");
exit(1);
}
if (argc < 3) usage();
service= argv[1];
progv= argv+2;
#else /* PARANOID */
int debug, i;
unsigned max_children;
arg0= argv[0];
debug= 0;
max_children= -1;
i= 1;
while (i < argc && argv[i][0] == '-') {
char *opt= argv[i++] + 1;
unsigned long m;
char *end;
if (*opt == '-' && opt[1] == 0) break; /* -- */
while (*opt != 0) switch (*opt++) {
case 'd':
debug= 1;
break;
case 'm':
if (*opt == 0) {
if (i == argc) usage();
opt= argv[i++];
}
m= strtoul(opt, &end, 10);
if (m <= 0 || m > UINT_MAX || *end != 0) usage();
max_children= m;
opt= "";
break;
default:
usage();
}
}
service= argv[i++];
progv= argv+i;
if (i >= argc) usage();
#endif
/* The interface to start the service on. */
if ((tcp_device= getenv("TCP_DEVICE")) == NULL) tcp_device= TCP_DEVICE;
/* Let SIGCHLD interrupt whatever I'm doing. */
sigemptyset(&chldmask);
sigaddset(&chldmask, SIGCHLD);
sigprocmask(SIG_BLOCK, &chldmask, &oldmask);
chldunmask= oldmask;
sigdelset(&chldunmask, SIGCHLD);
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_handler = sigchld;
sigaction(SIGCHLD, &sa, NULL);
/* Open a socket to the service I'm to serve. */
if ((servent= getservbyname(service, "tcp")) == NULL) {
unsigned long p;
char *end;
p= strtoul(service, &end, 0);
if (p <= 0 || p > 0xFFFF || *end != 0) {
fprintf(stderr, "%s: %s: Unknown service\n",
arg0, service);
exit(1);
}
port= htons((tcpport_t) p);
} else {
port= servent->s_port;
if (debug)
{
fprintf(stderr, "%s %s: listening to port %u\n",
arg0, service, ntohs(port));
}
}
/* No client yet. */
client_fd= -1;
while (1) {
if ((tcp_fd= open(tcp_device, O_RDWR)) < 0) {
report(tcp_device);
if (errno == ENOENT || errno == ENODEV
|| errno == ENXIO) {
exit(1);
}
goto bad;
}
tcpconf.nwtc_flags= NWTC_LP_SET | NWTC_UNSET_RA | NWTC_UNSET_RP;
tcpconf.nwtc_locport= port;
if (ioctl(tcp_fd, NWIOSTCPCONF, &tcpconf) < 0) {
report("Can't configure TCP channel");
exit(1);
}
tcpopt.nwto_flags= NWTO_DEL_RST;
if (ioctl(tcp_fd, NWIOSTCPOPT, &tcpopt) < 0) {
report("Can't set TCP options");
exit(1);
}
if (client_fd != -1) {
/* We have a client, so start a server for it. */
tcpopt.nwto_flags= 0;
(void) ioctl(client_fd, NWIOSTCPOPT, &tcpopt);
fflush(NULL);
/* Create a pipe to serve as an error indicator. */
if (pipe(pfd) < 0) {
report("pipe");
goto bad;
}
(void) fcntl(pfd[1], F_SETFD,
fcntl(pfd[1], F_GETFD) | FD_CLOEXEC);
/* Fork and exec. */
switch (fork()) {
case -1:
report("fork");
close(pfd[0]);
close(pfd[1]);
goto bad;
case 0:
close(tcp_fd);
close(pfd[0]);
#if PARANOID
/* Check if access to this service allowed. */
if (ioctl(client_fd, NWIOGTCPCONF, &tcpconf) == 0
&& tcpconf.nwtc_remaddr != tcpconf.nwtc_locaddr
&& !servxcheck(tcpconf.nwtc_remaddr, argv[1], NULL)
) {
exit(1);
}
#endif
sigprocmask(SIG_SETMASK, &oldmask, NULL);
dup2(client_fd, 0);
dup2(client_fd, 1);
close(client_fd);
execvp(progv[0], progv);
report(progv[0]);
write(pfd[1], &errno, sizeof(errno));
exit(1);
default:
nchildren++;
release(&client_fd);
close(pfd[1]);
r= read(pfd[0], &errno, sizeof(errno));
close(pfd[0]);
if (r != 0) goto bad;
break;
}
}
while (nchildren >= max_children) {
/* Too many clients, wait for one to die off. */
sigsuspend(&chldunmask);
}
/* Wait for a new connection. */
sigprocmask(SIG_UNBLOCK, &chldmask, NULL);
tcplistenopt.nwtcl_flags= 0;
while (ioctl(tcp_fd, NWIOTCPLISTEN, &tcplistenopt) < 0) {
if (errno != EINTR) {
if (errno != EAGAIN || debug) {
report("Unable to listen");
}
goto bad;
}
}
sigprocmask(SIG_BLOCK, &chldmask, NULL);
/* We got a connection. */
client_fd= tcp_fd;
tcp_fd= -1;
if (debug && ioctl(client_fd, NWIOGTCPCONF, &tcpconf) == 0) {
fprintf(stderr, "%s %s: Connection from %s:%u\n",
arg0, service,
inet_ntoa(tcpconf.nwtc_remaddr),
ntohs(tcpconf.nwtc_remport));
}
/* All is well, no need to stall. */
stall= 0;
continue;
bad:
/* All is not well, release resources. */
release(&tcp_fd);
release(&client_fd);
/* Wait a bit if this happens more than once. */
if (stall != 0) {
if (debug) {
fprintf(stderr, "%s %s: stalling %u second%s\n",
arg0, service,
stall, stall == 1 ? "" : "s");
}
sleep(stall);
stall <<= 1;
} else {
stall= 1;
}
}
}