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* Networking abstraction in PuTTY.
* 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 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.
typedef struct config_tag Config;
typedef struct backend_tag Backend;
typedef struct terminal_tag Terminal;
typedef struct SockAddr_tag *SockAddr;
/* pay attention to levels of indirection */
typedef struct socket_function_table **Socket;
typedef struct plug_function_table **Plug;
typedef void *OSSocket;
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);
int (*write) (Socket s, const char *data, int len);
int (*write_oob) (Socket s, const char *data, int len);
void (*flush) (Socket s);
void (*set_private_ptr) (Socket s, void *ptr);
void *(*get_private_ptr) (Socket s);
void (*set_frozen) (Socket s, int is_frozen);
/* ignored by tcp, but vital for ssl */
const char *(*socket_error) (Socket s);
struct plug_function_table {
void (*log)(Plug p, int type, SockAddr addr, int port,
const char *error_msg, int error_code);
* Passes the client progress reports on the process of setting
* up the connection.
* - type==0 means we are about to try to connect to address
* `addr' (error_msg and error_code are ignored)
* - type==1 means we have failed to connect to address `addr'
* (error_msg and error_code are supplied). This is not a
* fatal error - we may well have other candidate addresses
* to fall back to. When it _is_ fatal, the closing()
* function will be called.
int (*closing)
(Plug p, const 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.
void (*sent) (Plug p, int bufsize);
* The `sent' function is called when the pending send backlog
* on a socket is cleared or partially cleared. The new backlog
* size is passed in the `bufsize' parameter.
int (*accepting)(Plug p, OSSocket sock);
* returns 0 if the host at address addr is a valid host for connecting or error
/* proxy indirection layer */
/* NB, control of 'addr' is passed via new_connection, which takes
* responsibility for freeing it */
Socket new_connection(SockAddr addr, char *hostname,
int port, int privport,
int oobinline, int nodelay, int keepalive,
Plug plug, const Config *cfg);
Socket new_listener(char *srcaddr, int port, Plug plug, int local_host_only,
const Config *cfg, int addressfamily);
SockAddr name_lookup(char *host, int port, char **canonicalname,
const Config *cfg, int addressfamily);
/* platform-dependent callback from new_connection() */
/* (same caveat about addr as new_connection()) */
Socket platform_new_connection(SockAddr addr, char *hostname,
int port, int privport,
int oobinline, int nodelay, int keepalive,
Plug plug, const Config *cfg);
/* socket functions */
void sk_init(void); /* called once at program startup */
void sk_cleanup(void); /* called just before program exit */
SockAddr sk_namelookup(const char *host, char **canonicalname, int address_family);
SockAddr sk_nonamelookup(const char *host);
void sk_getaddr(SockAddr addr, char *buf, int buflen);
int sk_hostname_is_local(char *name);
int sk_address_is_local(SockAddr addr);
int sk_addrtype(SockAddr addr);
void sk_addrcopy(SockAddr addr, char *buf);
void sk_addr_free(SockAddr addr);
/* sk_addr_dup generates another SockAddr which contains the same data
* as the original one and can be freed independently. May not actually
* physically _duplicate_ it: incrementing a reference count so that
* one more free is required before it disappears is an acceptable
* implementation. */
SockAddr sk_addr_dup(SockAddr addr);
/* NB, control of 'addr' is passed via sk_new, which takes responsibility
* for freeing it, as for new_connection() */
Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
int nodelay, int keepalive, Plug p);
Socket sk_newlistener(char *srcaddr, int port, Plug plug, int local_host_only, int address_family);
Socket sk_register(OSSocket sock, Plug plug);
#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))
#define plug_log(p,type,addr,port,msg,code) (((*p)->log) (p, type, addr, port, msg, code))
#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))
#define plug_sent(p,bufsize) (((*p)->sent) (p, bufsize))
#define plug_accepting(p, sock) (((*p)->accepting)(p, sock))
* 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.
#define sk_set_private_ptr(s, ptr) (((*s)->set_private_ptr) (s, ptr))
#define sk_get_private_ptr(s) (((*s)->get_private_ptr) (s))
* Special error values are returned from sk_namelookup and sk_new
* if there's a problem. These functions extract an error message,
* or return NULL if there's no problem.
const char *sk_addr_error(SockAddr addr);
#define sk_socket_error(s) (((*s)->socket_error) (s))
* Set the `frozen' flag on a socket. A frozen socket is one in
* which all READABLE notifications are ignored, so that data is
* not accepted from the peer until the socket is unfrozen. This
* exists for two purposes:
* - Port forwarding: when a local listening port receives a
* connection, we do not want to receive data from the new
* socket until we have somewhere to send it. Hence, we freeze
* the socket until its associated SSH channel is ready; then we
* unfreeze it and pending data is delivered.
* - Socket buffering: if an SSH channel (or the whole connection)
* backs up or presents a zero window, we must freeze the
* associated local socket in order to avoid unbounded buffer
* growth.
#define sk_set_frozen(s, is_frozen) (((*s)->set_frozen) (s, is_frozen))
* Call this after an operation that might have tried to send on a
* socket, to clean up any pending network errors.
void net_pending_errors(void);
* Simple wrapper on getservbyname(), needed by ssh.c. Returns the
* port number, in host byte order (suitable for printf and so on).
* Returns 0 on failure. Any platform not supporting getservbyname
* can just return 0 - this function is not required to handle
* numeric port specifications.
int net_service_lookup(char *service);
* Look up the local hostname; return value needs freeing.
* May return NULL.
char *get_hostname(void);
/********** 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))