System/Shell/Commands: Add telnet

System/Shell/Commands/telnet.HC

@@ -0,0 +1,142 @@
+// A very dumb, not-quite-Telnet program for testing purposes
+// If running from a VM, on the host you can do something like:
+
+// socat TCP-LISTEN:2323,bind=10.20.0.254,reuseaddr,fork EXEC:"/bin/bash",pty,stderr,setsid,sigint,sane
+
+// and connect to the host from Erythros with "telnet 10.20.0.254 2323"
+
+#define TELNET_WILL 251
+#define TELNET_WONT 252
+#define TELNET_DO 253
+#define TELNET_DONT 254
+#define TELNET_IAC 255
+
+#define TELNET_CONNECTION_TIMED_OUT cnts.jiffies > ts_begin + ts_timeout
+
+class TelnetSession {
+    @shell* sh;
+    TlsSocket* s;
+};
+
+I64 @telnet_ignore_commands(U8* buf)
+{
+    I64 i = 0;
+    while (buf[i] == TELNET_IAC) {
+        switch (buf[i + 1]) {
+        case TELNET_WILL:
+        case TELNET_WONT:
+            buf[i + 1] = TELNET_DONT;
+            break;
+        case TELNET_DO:
+        case TELNET_DONT:
+            buf[i + 1] = TELNET_WONT;
+            break;
+        }
+        i += 3;
+    }
+    return i;
+}
+
+U0 @telnet_session(TelnetSession* session)
+{
+    U8 chars[1040];
+    U8* buf = &chars;
+    I64 cnt = 1;
+    I64 i;
+
+    while (cnt && session->s->state != TCP_SOCKET_STATE_CLOSED) {
+        cnt = session->s->receive(buf, 1024);
+        if (cnt) {
+            buf[cnt] = NULL;
+            i = 0;
+            while (i < cnt) {
+                switch (buf[i]) {
+                case TELNET_IAC:
+                    i += @telnet_ignore_commands(buf);
+                    session->s->send(buf, i);
+                    buf += i;
+                    break;
+                default:
+                    Stdio.WriteLine(session->sh, buf);
+                    i = cnt;
+                    break;
+                }
+            }
+        }
+        Sleep(1);
+    }
+}
+
+U0 @telnet_handle_input(@shell* sh, TlsSocket* s)
+{
+    U8 buf[128];
+    I64 len = 0;
+    while (FifoU8Cnt(sh->input))
+        FifoU8Rem(sh->input, buf + len++);
+    if (len)
+        s->send(buf, len);
+}
+
+I64 @shell_cmd_telnet(@shell* sh, I64 argc, U8** argv)
+{
+    if (argc < 2) {
+        Stdio.WriteLine(sh, "Usage: telnet host [port]\n");
+        return 1;
+    }
+
+    U8 buf[128];
+    U8* host = argv[1];
+    I64 port = 23;
+    if (argc > 2) {
+        port = Str2I64(argv[2]);
+    }
+
+    I64 ts_begin = 0;
+    I64 ts_timeout = 10000;
+
+    if (!host || !StrLen(host)) {
+        Stdio.WriteLine(sh, "telnet: Invalid host specified\n");
+        return 1;
+    }
+
+    if (@dns_query(host) == U32_MAX) {
+        Stdio.WriteLine(sh, "telnet: Host not found: %s\n", host);
+        return 1;
+    }
+
+    StrPrint(buf, "Trying %s port %d...\n", host, port);
+    Stdio.WriteLine(sh, buf);
+
+    TelnetSession session;
+    session.sh = sh;
+    session.s = @tcp_socket_create(host, port);
+    ts_begin = cnts.jiffies;
+
+    while (!sh->break && session.s->state != TCP_SOCKET_STATE_ESTABLISHED && !(TELNET_CONNECTION_TIMED_OUT)) {
+        Sleep(1);
+    }
+
+    if (sh->break) {
+        session.s->close();
+        return 1;
+    }
+
+    if (TELNET_CONNECTION_TIMED_OUT) {
+        Stdio.WriteLine(sh, "Connection timed out.\n");
+        session.s->close();
+        return 1;
+    }
+
+    StrPrint(buf, "Connected to %s.\n", host);
+    Stdio.WriteLine(sh, buf);
+
+    Spawn(&@telnet_session, &session);
+
+    while (session.s->state != TCP_SOCKET_STATE_CLOSED) {
+        @telnet_handle_input(sh, session.s);
+        Sleep(1);
+    }
+
+    Stdio.WriteLine(sh, "Connection closed by foreign host.\n");
+    return 1;
+}