Add openconnect_set_cancel_fd() to library

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

Makefile.am

@@ -21,7 +21,7 @@ library_srcs = ssl.c http.c auth.c library.c compat.c
 libopenconnect_la_SOURCES = version.c $(library_srcs)
 libopenconnect_la_CFLAGS = $(OPENSSL_CFLAGS) $(LIBXML2_CFLAGS) $(LIBPROXY_CFLAGS)
 libopenconnect_la_LIBADD = $(OPENSSL_LIBS) $(LIBXML2_LIBS) $(LIBPROXY_LIBS) $(LIBINTL)
-libopenconnect_la_LDFLAGS = -version-number 1:2
+libopenconnect_la_LDFLAGS = -version-number 1:4
 noinst_HEADERS = openconnect-internal.h openconnect.h
 include_HEADERS = openconnect.h
 

library.c

@@ -204,6 +204,11 @@ void openconnect_set_cert_expiry_warning (struct openconnect_info *vpninfo,
 	vpninfo->cert_expire_warning = seconds;
 }
 
+void openconnect_set_cancel_fd (struct openconnect_info *vpninfo, int fd)
+{
+	vpninfo->cancel_fd = fd;
+}
+
 const char *openconnect_get_version (void)
 {
 	return openconnect_version;

openconnect.h

@@ -31,9 +31,12 @@
 #include <unistd.h>
 
 #define OPENCONNECT_API_VERSION_MAJOR 1
-#define OPENCONNECT_API_VERSION_MINOR 3
+#define OPENCONNECT_API_VERSION_MINOR 4
 
 /*
+ * API version 1.4:
+ *  - Add openconnect_set_cancel_fd()
+ *
  * API version 1.3:
  *  - Add openconnect_set_cert_expiry_warning() to change from default 60 days
  *
@@ -138,6 +141,18 @@ void openconnect_reset_ssl (struct openconnect_info *vpninfo);
 int openconnect_parse_url (struct openconnect_info *vpninfo, char *url);
 void openconnect_set_cert_expiry_warning (struct openconnect_info *vpninfo,
 					  int seconds);
+
+/* If this is set, then openconnect_obtain_cookie() will abort and return
+   failure if the file descriptor is readable. Typically a user may create
+   a pair of pipes with the pipe(2) system call, hand the readable one to
+   this function, and then write a byte to the other end if it ever wants
+   to cancel the connection. This way, a multi-threaded UI (which will be
+   running openconnect_obtain_cookie() in a separate thread since it blocks)
+   has the ability to cancel that call, reap its thread and free the
+   vpninfo structure (or retry). An 'fd' argument of -1 will render the
+   cancellation mechanism inactive. */
+void openconnect_set_cancel_fd (struct openconnect_info *vpninfo, int fd);
+
 const char *openconnect_get_version(void);
 
 /* The first (privdata) argument to each of these functions is either