Move TCP closure detection to cstp.c, make it reconnect when it happens

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

cstp.c

@@ -502,6 +502,14 @@ int cstp_mainloop(struct openconnect_info *vpninfo, int *timeout)
 		return 1;
 	}
 
+	ret = SSL_get_error(vpninfo->https_ssl, len);
+	if (ret == SSL_ERROR_SYSCALL || ret == SSL_ERROR_ZERO_RETURN) {
+		vpninfo->progress(vpninfo, PRG_ERR,
+				  "SSL read error %d (server probably closed connection); reconnecting.\n",
+				  ret);
+			goto do_reconnect;
+	}
+
 
 	/* If SSL_write() fails we are expected to try again. With exactly
 	   the same data, at exactly the same location. So we keep the

mainloop.c

@@ -127,15 +127,8 @@ int vpn_mainloop(struct openconnect_info *vpninfo)
 
 		tv.tv_sec = timeout / 1000;
 		tv.tv_usec = (timeout % 1000) * 1000;
-		if (select(vpninfo->select_nfds, &rfds, &wfds, &efds, &tv) >= 0
-		    && FD_ISSET(vpninfo->ssl_fd, &rfds)) {
-			char b;
-			if (recv(vpninfo->ssl_fd, &b, 1, MSG_PEEK) == 0) {
-				/* Zero indicates EOF, which OpenSSL won't handle on read() */
-				vpninfo->progress(vpninfo, PRG_ERR, "Server closed connection!\n");
-				exit(1);
-			}
-		}
+
+		select(vpninfo->select_nfds, &rfds, &wfds, &efds, &tv);
 	}
 
 	cstp_bye(vpninfo, vpninfo->quit_reason);