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/* netcat.c - Forward stdin/stdout to a file or network connection.
*
* Copyright 2007 Rob Landley <rob@landley.net>
*
* TODO: udp, ipv6, genericize for telnet/microcom/tail-f
USE_NETCAT(OLDTOY(nc, netcat, USE_NETCAT_LISTEN("tl^L^")"w#p#s:q#f:", TOYFLAG_BIN))
USE_NETCAT(NEWTOY(netcat, USE_NETCAT_LISTEN("tl^L^")"w#p#s:q#f:", TOYFLAG_BIN))
config NETCAT
bool "netcat"
default y
help
usage: netcat [-u] [-wpq #] [-s addr] {IPADDR PORTNUM|-f FILENAME}
-f use FILENAME (ala /dev/ttyS0) instead of network
-p local port number
-q SECONDS quit this many seconds after EOF on stdin.
-s local ipv4 address
-w SECONDS timeout for connection
Use "stty 115200 -F /dev/ttyS0 && stty raw -echo -ctlecho" with
netcat -f to connect to a serial port.
config NETCAT_LISTEN
bool "netcat server options (-let)"
default y
depends on NETCAT
depends on TOYBOX_PTY
help
usage: netcat [-t] [-lL COMMAND...]
-t allocate tty (must come before -l or -L)
-l listen for one incoming connection.
-L listen for multiple incoming connections (server mode).
The command line after -l or -L is executed to handle each incoming
connection. If none, the connection is forwarded to stdin/stdout.
For a quick-and-dirty server, try something like:
netcat -s 127.0.0.1 -p 1234 -tL /bin/bash -l
*/
#define FOR_netcat
#include "toys.h"
GLOBALS(
char *filename; // -f read from filename instead of network
long quit_delay; // -q Exit after EOF from stdin after # seconds.
char *source_address; // -s Bind to a specific source address.
long port; // -p Bind to a specific source port.
long wait; // -w Wait # seconds for a connection.
)
static void timeout(int signum)
{
if (TT.wait) error_exit("Timeout");
exit(0);
}
static void set_alarm(int seconds)
{
signal(SIGALRM, seconds ? timeout : SIG_DFL);
alarm(seconds);
}
// Translate x.x.x.x numeric IPv4 address, or else DNS lookup an IPv4 name.
static void lookup_name(char *name, uint32_t *result)
{
struct hostent *hostbyname;
hostbyname = gethostbyname(name); // getaddrinfo
if (!hostbyname) error_exit("no host '%s'", name);
*result = *(uint32_t *)*hostbyname->h_addr_list;
}
// Worry about a fancy lookup later.
static void lookup_port(char *str, uint16_t *port)
{
*port = SWAP_BE16(atoi(str));
}
void netcat_main(void)
{
int sockfd=-1, pollcount=2;
struct pollfd pollfds[2];
memset(pollfds, 0, 2*sizeof(struct pollfd));
pollfds[0].events = pollfds[1].events = POLLIN;
set_alarm(TT.wait);
// The argument parsing logic can't make "<2" conditional on other
// arguments like -f and -l, so we do it by hand here.
if (toys.optflags&FLAG_f) {
if (toys.optc) toys.exithelp++;
} else if (!(toys.optflags&(FLAG_l|FLAG_L)) && toys.optc!=2) toys.exithelp++;
if (toys.exithelp) error_exit("Argument count wrong");
if (TT.filename) pollfds[0].fd = xopen(TT.filename, O_RDWR);
else {
int temp;
struct sockaddr_in address;
// Setup socket
sockfd = xsocket(AF_INET, SOCK_STREAM, 0);
fcntl(sockfd, F_SETFD, FD_CLOEXEC);
temp = 1;
setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &temp, sizeof(temp));
memset(&address, 0, sizeof(address));
address.sin_family = AF_INET;
if (TT.source_address || TT.port) {
address.sin_port = SWAP_BE16(TT.port);
if (TT.source_address)
lookup_name(TT.source_address, (uint32_t *)&address.sin_addr);
if (bind(sockfd, (struct sockaddr *)&address, sizeof(address)))
perror_exit("bind");
}
// Dial out
if (!CFG_NETCAT_LISTEN || !(toys.optflags&(FLAG_L|FLAG_l))) {
// Figure out where to dial out to.
lookup_name(*toys.optargs, (uint32_t *)&address.sin_addr);
lookup_port(toys.optargs[1], &address.sin_port);
temp = connect(sockfd, (struct sockaddr *)&address, sizeof(address));
if (temp<0) perror_exit("connect");
pollfds[0].fd = sockfd;
// Listen for incoming connections
} else {
socklen_t len = sizeof(address);
if (listen(sockfd, 5)) error_exit("listen");
if (!TT.port) {
getsockname(sockfd, (struct sockaddr *)&address, &len);
printf("%d\n", SWAP_BE16(address.sin_port));
fflush(stdout);
}
// Do we need to return immediately because -l has arguments?
if ((toys.optflags & FLAG_l) && toys.optc) {
if (xfork()) goto cleanup;
close(0);
close(1);
close(2);
}
for (;;) {
pid_t child = 0;
// For -l, call accept from the _new_ process.
pollfds[0].fd = accept(sockfd, (struct sockaddr *)&address, &len);
if (pollfds[0].fd<0) perror_exit("accept");
// Do we need a tty?
if (toys.optflags&FLAG_t)
child = forkpty(&(pollfds[1].fd), NULL, NULL, NULL);
// Do we need to fork and/or redirect for exec?
else {
if (toys.optflags&FLAG_L) child = fork();
if (!child && toys.optc) {
int fd = pollfds[0].fd;
dup2(fd, 0);
dup2(fd, 1);
if (toys.optflags&FLAG_L) dup2(fd, 2);
if (fd>2) close(fd);
}
}
if (child<0) error_msg("Fork failed\n");
if (child<1) break;
close(pollfds[0].fd);
}
}
}
// We have a connection. Disarm timeout.
// (Does not play well with -L, but what _should_ that do?)
set_alarm(0);
if (CFG_NETCAT_LISTEN && (toys.optflags&(FLAG_L|FLAG_l) && toys.optc))
xexec_optargs(0);
// Poll loop copying stdin->socket and socket->stdout.
for (;;) {
int i;
if (0>poll(pollfds, pollcount, -1)) perror_exit("poll");
for (i=0; i<pollcount; i++) {
if (pollfds[i].revents & POLLIN) {
int len = read(pollfds[i].fd, toybuf, sizeof(toybuf));
if (len<1) goto dohupnow;
xwrite(i ? pollfds[0].fd : 1, toybuf, len);
} else if (pollfds[i].revents & POLLHUP) {
dohupnow:
// Close half-connection. This is needed for things like
// "echo GET / | netcat landley.net 80"
if (i) {
shutdown(pollfds[0].fd, SHUT_WR);
pollcount--;
set_alarm(TT.quit_delay);
} else goto cleanup;
}
}
}
cleanup:
if (CFG_TOYBOX_FREE) {
close(pollfds[0].fd);
close(sockfd);
}
}
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