Dave Hinton's modifications to the network layer interface, which

should make it possible to add SSL support later.

[originally from svn r996]

network.h

@@ -3,52 +3,78 @@
  *
  * The way this works is: a back end can choose to open any number
  * of sockets - including zero, which might be necessary in some.
- * It can register a function to be called when data comes in on
- * any given one, and it can call the networking abstraction to
- * send data without having to worry about blocking. The stuff
- * behind the abstraction takes care of selects and nonblocking
- * writes and all that sort of painful gubbins.
+ * It can register a bunch of callbacks (most notably for when 
+ * data is received) for each socket, and it can call the networking
+ * abstraction to send data without having to worry about blocking.
+ * The stuff behind the abstraction takes care of selects and
+ * nonblocking writes and all that sort of painful gubbins.
  */
 
 #ifndef PUTTY_NETWORK_H
 #define PUTTY_NETWORK_H
 
-typedef struct Socket_tag *Socket;
 typedef struct SockAddr_tag *SockAddr;
+/* pay attention to levels of indirection */
+typedef struct socket_function_table **Socket;
+typedef struct plug_function_table **Plug;
+
+struct socket_function_table {
+    Plug (*plug) (Socket s, Plug p);
+	/* use a different plug (return the old one) */
+	/* if p is NULL, it doesn't change the plug */
+	/* but it does return the one it's using */
+    void (*close) (Socket s);
+    void (*write) (Socket s, char *data, int len);
+    void (*write_oob) (Socket s, char *data, int len);
+    void (*flush) (Socket s);
+	/* ignored by tcp, but vital for ssl */
+    char *(*socket_error) (Socket s);
+};
+
+struct plug_function_table {
+    int (*closing)
+	(Plug p, char *error_msg, int error_code, int calling_back);
+	/* error_msg is NULL iff it is not an error (ie it closed normally) */
+	/* calling_back != 0 iff there is a Plug function */
+	/* currently running (would cure the fixme in try_send()) */
+    int (*receive) (Plug p, int urgent, char *data, int len);
+	/*
+	 *  - urgent==0. `data' points to `len' bytes of perfectly
+	 *    ordinary data.
+	 * 
+	 *  - urgent==1. `data' points to `len' bytes of data,
+	 *    which were read from before an Urgent pointer.
+	 * 
+	 *  - urgent==2. `data' points to `len' bytes of data,
+	 *    the first of which was the one at the Urgent mark.
+	 */
+};
 
-/*
- * This is the function a client must register with each socket, to
- * receive data coming in on that socket. The parameter `urgent'
- * decides the meaning of `data' and `len':
- * 
- *  - urgent==0. `data' points to `len' bytes of perfectly ordinary
- *    data.
- * 
- *  - urgent==1. `data' points to `len' bytes of data, which were
- *    read from before an Urgent pointer.
- * 
- *  - urgent==2. `data' points to `len' bytes of data, the first of
- *    which was the one at the Urgent mark.
- * 
- *  - urgent==3. An error has occurred on the socket. `data' points
- *    to an error string, and `len' points to an error code.
- */
-typedef int (*sk_receiver_t)(Socket s, int urgent, char *data, int len);
 
 void sk_init(void);		       /* called once at program startup */
 
 SockAddr sk_namelookup(char *host, char **canonicalname);
 void sk_addr_free(SockAddr addr);
 
-Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
-              sk_receiver_t receiver);
-void sk_close(Socket s);
-void sk_write(Socket s, char *buf, int len);
-void sk_write_oob(Socket s, char *buf, int len);
+Socket sk_new(SockAddr addr, int port, int privport, int oobinline, Plug p);
+
+#define sk_plug(s,p) (((*s)->plug) (s, p))
+#define sk_close(s) (((*s)->close) (s))
+#define sk_write(s,buf,len) (((*s)->write) (s, buf, len))
+#define sk_write_oob(s,buf,len) (((*s)->write_oob) (s, buf, len))
+#define sk_flush(s) (((*s)->flush) (s))
+
+#ifdef DEFINE_PLUG_METHOD_MACROS
+#define plug_closing(p,msg,code,callback) (((*p)->closing) (p, msg, code, callback))
+#define plug_receive(p,urgent,buf,len) (((*p)->receive) (p, urgent, buf, len))
+#endif
 
 /*
  * Each socket abstraction contains a `void *' private field in
  * which the client can keep state.
+ *
+ * This is perhaps unnecessary now that we have the notion of a plug,
+ * but there is some existing code that uses it, so it stays.
  */
 void sk_set_private_ptr(Socket s, void *ptr);
 void *sk_get_private_ptr(Socket s);
@@ -59,6 +85,46 @@ void *sk_get_private_ptr(Socket s);
  * or return NULL if there's no problem.
  */
 char *sk_addr_error(SockAddr addr);
-char *sk_socket_error(Socket addr);
+#define sk_socket_error(s) (((*s)->socket_error) (s))
+
+
+/********** SSL stuff **********/
+
+/*
+ * This section is subject to change, but you get the general idea
+ * of what it will eventually look like.
+ */
+
+
+typedef struct certificate *Certificate;
+typedef struct our_certificate *Our_Certificate;
+    /* to be defined somewhere else, somehow */
+
+typedef struct ssl_client_socket_function_table **SSL_Client_Socket;
+typedef struct ssl_client_plug_function_table **SSL_Client_Plug;
+
+struct ssl_client_socket_function_table {
+    struct socket_function_table base;
+    void (*renegotiate) (SSL_Client_Socket s);
+	/* renegotiate the cipher spec */
+};
+
+struct ssl_client_plug_function_table {
+    struct plug_function_table base;
+    int (*refuse_cert) (SSL_Client_Plug p, Certificate cert[]);
+	/* do we accept this certificate chain?  If not, why not? */
+	/* cert[0] is the server's certificate, cert[] is NULL-terminated */
+	/* the last certificate may or may not be the root certificate */
+    Our_Certificate (*client_cert) (SSL_Client_Plug p);
+	/* the server wants us to identify ourselves */
+	/* may return NULL if we want anonymity */
+};
+
+SSL_Client_Socket sk_ssl_client_over (
+    Socket s, /* pre-existing (tcp) connection */
+    SSL_Client_Plug p
+);
+
+#define sk_renegotiate(s) (((*s)->renegotiate) (s))
 
 #endif