1 /* netcat.c - Forward stdin/stdout to a file or network connection.
2 *
3 * Copyright 2007 Rob Landley <rob@landley.net>
4 *
5 * TODO: genericize for telnet/microcom/tail-f, fix -t
6
7 USE_NETCAT(NEWTOY(netcat, "^tElLw#<1W#<1p#<1>65535q#<1s:f:46uUn[!tlL][!Lw][!Lu][!46U]", TOYFLAG_BIN))
8 USE_NETCAT(OLDTOY(nc, netcat, TOYFLAG_USR|TOYFLAG_BIN))
9
10 config NETCAT
11 bool "netcat"
12 default y
13 help
14 usage: netcat [-46ElLtUu] [-wpq #] [-s addr] {IPADDR PORTNUM|-f FILENAME|COMMAND...}
15
16 Forward stdin/stdout to a file or network connection.
17
18 -4 Force IPv4
19 -6 Force IPv6
20 -E Forward stderr
21 -f Use FILENAME (ala /dev/ttyS0) instead of network
22 -l Listen for one incoming connection, then exit
23 -L Listen and background each incoming connection (server mode)
24 -n No DNS lookup
25 -p Local port number
26 -q Quit SECONDS after EOF on stdin, even if stdout hasn't closed yet
27 -s Local source address
28 -t Allocate tty
29 -u Use UDP
30 -U Use a UNIX domain socket
31 -w SECONDS timeout to establish connection
32 -W SECONDS timeout for more data on an idle connection
33
34 When listening the COMMAND line is executed as a child process to handle
35 an incoming connection. With no COMMAND -l forwards the connection
36 to stdin/stdout. If no -p specified, -l prints the port it bound to and
37 backgrounds itself (returning immediately).
38
39 For a quick-and-dirty server, try something like:
40 netcat -s 127.0.0.1 -p 1234 -tL sh -l
41
42 Or use "stty 115200 -F /dev/ttyS0 && stty raw -echo -ctlecho" with
43 netcat -f to connect to a serial port.
44 */
45
46 #define FOR_netcat
47 #include "toys.h"
48
49 GLOBALS(
50 char *f, *s;
51 long q, p, W, w;
52 )
53
timeout(int signum)54 static void timeout(int signum)
55 {
56 if (TT.w) error_exit("Timeout");
57 xexit();
58 }
59
60 // open AF_UNIX socket
usock(char * name,int type,int out)61 static int usock(char *name, int type, int out)
62 {
63 int sockfd;
64 struct sockaddr_un sockaddr;
65
66 memset(&sockaddr, 0, sizeof(struct sockaddr_un));
67
68 if (strlen(name) + 1 > sizeof(sockaddr.sun_path))
69 error_exit("socket path too long %s", name);
70 strcpy(sockaddr.sun_path, name);
71 sockaddr.sun_family = AF_UNIX;
72
73 sockfd = xsocket(AF_UNIX, type, 0);
74 (out?xconnect:xbind)(sockfd, (struct sockaddr*)&sockaddr, sizeof(sockaddr));
75
76 return sockfd;
77 }
78
netcat_main(void)79 void netcat_main(void)
80 {
81 int sockfd = -1, in1 = 0, in2 = 0, out1 = 1, out2 = 1, family = AF_UNSPEC,
82 type = FLAG(u) ? SOCK_DGRAM : SOCK_STREAM;
83 socklen_t len;
84 pid_t child;
85
86 // Addjust idle and quit_delay to ms or -1 for no timeout
87 TT.W = TT.W ? TT.W*1000 : -1;
88 TT.q = TT.q ? TT.q*1000 : -1;
89
90 xsignal(SIGCHLD, SIG_IGN);
91 if (TT.w) {
92 xsignal(SIGALRM, timeout);
93 alarm(TT.w);
94 }
95
96 // The argument parsing logic can't make "<2" conditional on other
97 // arguments like -f and -l, so do it by hand here.
98 if (FLAG(f) ? toys.optc : (!FLAG(l) && !FLAG(L) && toys.optc!=2-FLAG(U)))
99 help_exit("bad argument count");
100
101 if (FLAG(4)) family = AF_INET;
102 else if (FLAG(6)) family = AF_INET6;
103 else if (FLAG(U)) family = AF_UNIX;
104
105 if (TT.f) in1 = out2 = xopen(TT.f, O_RDWR);
106 else {
107 // Setup socket
108 if (!FLAG(l) && !FLAG(L)) {
109 if (FLAG(U)) sockfd = usock(toys.optargs[0], type, 1);
110 else sockfd = xconnectany(xgetaddrinfo(toys.optargs[0],
111 toys.optargs[1], family, type, 0, AI_NUMERICHOST*FLAG(n)));
112
113 // We have a connection. Disarm timeout and start poll/send loop.
114 alarm(0);
115 in1 = out2 = sockfd;
116 pollinate(in1, in2, out1, out2, TT.W, TT.q);
117 } else {
118 // Listen for incoming connections
119 if (FLAG(U)) {
120 if (!FLAG(s)) error_exit("-s must be provided if using -U with -L/-l");
121 sockfd = usock(TT.s, type, 0);
122 } else {
123 sprintf(toybuf, "%ld", TT.p);
124 sockfd = xbindany(xgetaddrinfo(TT.s, toybuf, family, type, 0, 0));
125 }
126
127 if (!FLAG(u) && listen(sockfd, 5)) perror_exit("listen");
128 if (!TT.p && !FLAG(U)) {
129 struct sockaddr* address = (void*)toybuf;
130 short port_be;
131
132 len = sizeof(struct sockaddr_storage);
133 getsockname(sockfd, address, &len);
134 if (address->sa_family == AF_INET)
135 port_be = ((struct sockaddr_in*)address)->sin_port;
136 else if (address->sa_family == AF_INET6)
137 port_be = ((struct sockaddr_in6*)address)->sin6_port;
138 else perror_exit("getsockname: bad family");
139
140 dprintf(1, "%d\n", SWAP_BE16(port_be));
141 // Return immediately if no -p and -Ll has arguments, so wrapper
142 // script can use port number.
143 if (CFG_TOYBOX_FORK && toys.optc && xfork()) goto cleanup;
144 }
145
146 do {
147 len = sizeof(struct sockaddr_storage);
148 if (FLAG(u)) {
149 if (-1 == recvfrom(in1 = dup(sockfd), &child, 1, MSG_PEEK,
150 (void *)toybuf, &len)) perror_exit("recvfrom");
151 } else if ((in1 = accept(sockfd, 0, 0))<0) perror_exit("accept");
152 out2 = in1;
153 child = 0;
154
155 // We have a connection. Disarm timeout.
156 alarm(0);
157
158 // Fork a child as necessary. Parent cleans up and continues here.
159 if (toys.optc && FLAG(L)) NOEXIT(child = XVFORK());
160 if (child) {
161 close(in1);
162 continue;
163 }
164
165 if (FLAG(u))
166 xconnect(in1, (void *)toybuf, sizeof(struct sockaddr_storage));
167
168 // Cleanup and redirect for exec
169 if (toys.optc) {
170 // Do we need a tty?
171 // TODO nommu and -t only affects server mode...
172 // if (FLAG(t)) child = forkpty(&fdout, NULL, NULL, NULL);
173
174 close(sockfd);
175 dup2(in1, 0);
176 dup2(in1, 1);
177 if (FLAG(E)) dup2(in1, 2);
178 if (in1>2) close(in1);
179 xexec(toys.optargs);
180
181 // Copy stdin/out
182 } else {
183 pollinate(in1, in2, out1, out2, TT.W, TT.q);
184 close(in1);
185 }
186 } while (FLAG(L));
187 }
188 }
189
190 cleanup:
191 if (CFG_TOYBOX_FREE) {
192 close(in1);
193 close(sockfd);
194 }
195 }
196