Add port redirection option for networking with slirp.

Port forwarding allows the emulator to host servers that can be
accessed from outside the virtual network.

The code for parsing the preference option "redir" is adapted from
qemu code. The rest was already implemented.

BasiliskII/README

@@ -528,6 +528,18 @@ udpport <IP port number>
   This item specifies the IP port number to use for the "UDP Tunnel" mode.
   The default is 6066.
 
+redir <port redirection description>
+
+  This item defines a port to be forwarded from the host to the client. 
+  The format is "[protocol]:hostport:[clientaddress]:clientport", where
+  protocol is "udp" or "tcp" (default), hostport is the port on your
+  computer to forward to the Mac, clientaddress is the IP address of the Mac
+  in the virtual network (defaults to 10.0.2.15), and clientport is the port on
+  the Mac to be exposed. For example, if you have a web server in MacOS running
+  on port 80, you can expose it as port 8000 with the line below:
+
+  redir tcp:8000:10.0.2.15:80
+
 rom <ROM file path>
 
   This item specifies the file name of the Mac ROM file to be used by

BasiliskII/src/Unix/ether_unix.cpp

@@ -66,6 +66,7 @@
 
 #ifdef HAVE_SLIRP
 #include "libslirp.h"
+#include "ctl.h"
 #endif
 
 #include "cpu_emulation.h"
@@ -131,6 +132,8 @@ static int16 ether_do_add_multicast(uint8 *addr);
 static int16 ether_do_del_multicast(uint8 *addr);
 static int16 ether_do_write(uint32 arg);
 static void ether_do_interrupt(void);
+static void slirp_add_redirs();
+static int slirp_add_redir(const char *redir_str);
 
 
 /*
@@ -279,6 +282,9 @@ bool ether_init(void)
 		// Open slirp input pipe
 		if (pipe(slirp_input_fds) < 0)
 			return false;
+
+		// Set up port redirects
+		slirp_add_redirs();
 	}
 #endif
 
@@ -951,3 +957,95 @@ void ether_do_interrupt(void)
 		}
 	}
 }
+
+// Helper function for port forwarding
+static int get_str_sep(char *buf, int buf_size, const char **pp, int sep)
+{
+	const char *p, *p1;
+	int len;
+	p = *pp;
+	p1 = strchr(p, sep);
+	if (!p1)
+		return -1;
+	len = p1 - p;
+	p1++;
+	if (buf_size > 0) {
+		if (len > buf_size - 1)
+			len = buf_size - 1;
+		memcpy(buf, p, len);
+		buf[len] = '\0';
+	}
+	*pp = p1;
+	return 0;
+}
+
+// Set up port forwarding for slirp
+static void slirp_add_redirs()
+{
+	int index = 0;
+	const char *str;
+	while ((str = PrefsFindString("redir", index++)) != NULL) {
+		slirp_add_redir(str);
+	}
+}
+
+// Add a port forward/redirection for slirp
+static int slirp_add_redir(const char *redir_str)
+{
+	// code adapted from qemu source
+	struct in_addr guest_addr = { .s_addr = 0 };
+	int host_port, guest_port;
+	const char *p;
+	char buf[256];
+	int is_udp;
+	char *end;
+	char str[256];
+
+	p = redir_str;
+	if (!p || get_str_sep(buf, sizeof(buf), &p, ':') < 0) {
+		goto fail_syntax;
+	}
+	if (!strcmp(buf, "tcp") || buf[0] == '\0') {
+		is_udp = 0;
+	} else if (!strcmp(buf, "udp")) {
+		is_udp = 1;
+	} else {
+		goto fail_syntax;
+	}
+
+	if (get_str_sep(buf, sizeof(buf), &p, ':') < 0) {
+		goto fail_syntax;
+	}
+	host_port = strtol(buf, &end, 0);
+	if (*end != '\0' || host_port < 1 || host_port > 65535) {
+		goto fail_syntax;
+	}
+
+	if (get_str_sep(buf, sizeof(buf), &p, ':') < 0) {
+		goto fail_syntax;
+	}
+	// 0.0.0.0 doesn't seem to work, so default to a client address
+	// if none is specified
+	if (buf[0] == '\0' ?
+			!inet_aton(CTL_LOCAL, &guest_addr) :
+			!inet_aton(buf, &guest_addr)) {
+		goto fail_syntax;
+	}
+
+	guest_port = strtol(p, &end, 0);
+	if (*end != '\0' || guest_port < 1 || guest_port > 65535) {
+		goto fail_syntax;
+	}
+
+	if (slirp_redir(is_udp, host_port, guest_addr, guest_port) < 0) {
+		sprintf(str, "could not set up host forwarding rule '%s'", redir_str);
+		WarningAlert(str);
+		return -1;
+	}
+	return 0;
+
+ fail_syntax:
+	sprintf(str, "invalid host forwarding rule '%s'", redir_str);
+	WarningAlert(str);
+	return -1;
+}

BasiliskII/src/prefs_items.cpp

@@ -46,6 +46,7 @@ prefs_desc common_prefs_items[] = {
 	{"etherconfig", TYPE_STRING, false,"path of network config script"},
 	{"udptunnel", TYPE_BOOLEAN, false, "tunnel all network packets over UDP"},
 	{"udpport", TYPE_INT32, false,    "IP port number for tunneling"},
+	{"redir", TYPE_STRING, true,      "port forwarding for slirp"},
 	{"rom", TYPE_STRING, false,       "path of ROM file"},
 	{"bootdrive", TYPE_INT32, false,  "boot drive number"},
 	{"bootdriver", TYPE_INT32, false, "boot driver number"},