Add new helper functions to support cmd_fd feature

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>

openconnect-internal.h

@@ -298,6 +298,7 @@ struct openconnect_info {
 
 	int cmd_fd;
 	int cmd_fd_write;
+	int got_cancel_cmd;
 
 	struct pkt *incoming_queue;
 	struct pkt *outgoing_queue;
@@ -403,7 +404,9 @@ const char *keystore_strerror(int err);
 int keystore_fetch(const char *key, unsigned char **result);
 #endif
 void cmd_fd_set(struct openconnect_info *vpninfo, fd_set *fds, int *maxfd);
+void check_cmd_fd(struct openconnect_info *vpninfo, fd_set *fds);
 int is_cancel_pending(struct openconnect_info *vpninfo, fd_set *fds);
+void poll_cmd_fd(struct openconnect_info *vpninfo, int timeout);
 
 /* ${SSL_LIBRARY}.c */
 int openconnect_SSL_gets(struct openconnect_info *vpninfo, char *buf, size_t len);

openconnect.h

@@ -167,6 +167,9 @@ struct oc_auth_form {
 #define PRG_DEBUG	2
 #define PRG_TRACE	3
 
+/* byte commands to write into the cmd_fd */
+#define OC_CMD_CANCEL	'x'
+
 struct openconnect_info;
 
 #define OPENCONNECT_X509 void

ssl.c

@@ -530,7 +530,42 @@ void cmd_fd_set(struct openconnect_info *vpninfo, fd_set *fds, int *maxfd)
 	}
 }
 
+void check_cmd_fd(struct openconnect_info *vpninfo, fd_set *fds)
+{
+	char cmd;
+
+	if (vpninfo->cmd_fd == -1 || !FD_ISSET(vpninfo->cmd_fd, fds))
+		return;
+	if (vpninfo->cmd_fd_write == -1) {
+		/* legacy openconnect_set_cancel_fd() users */
+		vpninfo->got_cancel_cmd = 1;
+		return;
+	}
+
+	if (read(vpninfo->cmd_fd, &cmd, 1) != 1)
+		return;
+
+	switch (cmd) {
+	case OC_CMD_CANCEL:
+		vpninfo->got_cancel_cmd = 1;
+		break;
+	}
+}
+
 int is_cancel_pending(struct openconnect_info *vpninfo, fd_set *fds)
 {
-	return vpninfo->cmd_fd != -1 && FD_ISSET(vpninfo->cmd_fd, fds);
+	check_cmd_fd(vpninfo, fds);
+	return vpninfo->got_cancel_cmd;
+}
+
+void poll_cmd_fd(struct openconnect_info *vpninfo, int timeout)
+{
+	fd_set rd_set;
+	int maxfd = 0;
+	struct timeval tv = { timeout, 0 };
+
+	FD_ZERO(&rd_set);
+	cmd_fd_set(vpninfo, &rd_set, &maxfd);
+	select(maxfd + 1, &rd_set, NULL, NULL, &tv);
+	check_cmd_fd(vpninfo, &rd_set);
 }