httpd: clear upload reset intent when the TCP slot is reused

With UIP_CONF_MAX_CONNECTIONS set to one, a verified upload can leave
reset intent set when its response is never acknowledged. A subsequent
TCP connection reuses that slot, and ACKing its plain GET response can
otherwise trigger reset_chip(). This is sequential slot reuse, not
concurrent HTTP connections.

Store reset intent in the connection appstate and initialize both tstate
and fw_reset_pending on every uip_connected() event, regardless of stale
appstate contents. Reset only after the verified upload response is fully
acknowledged.

Exercise the real HTTP callback for all stale tstate bytes, sequential
slot reuse and a later GET, partial/final ACKs, abort, timeout and CRC
failure. Keep the regression tests in the existing tab-indented style.

httpd/httpd.c

@@ -75,9 +75,6 @@ __xdata uint8_t postbody_endpoint;
 __xdata uint16_t postbody_start;
 
 __xdata char passwd[21];
-// Set when a verified firmware upload awaits its response ACK, after
-// which the chip resets to apply the staged image
-__xdata uint8_t fw_reset_pending;
 __xdata char session_id[SESSION_ID_LENGTH + 1];
 __xdata uint8_t authenticated;
 __xdata uint32_t now;
@@ -110,7 +107,6 @@ void httpd_init(void) __banked
 	// Not through uip_conn: it only points at a connection while uIP is
 	// handling one, and nothing has set it yet at init time.
 	uip_conns[0].appstate.tstate = TSTATE_CLOSED;
-	fw_reset_pending = 0; // xdata is not zeroed by the startup code
 }
 
 
@@ -511,7 +507,7 @@ uint8_t stream_upload(void)
 						"Content-Type: text/plain\r\n\r\n"
 						"OK: checksum verified, rebooting\n");
 					// Reset once the response is fully ACKed
-					fw_reset_pending = 1;
+					s->fw_reset_pending = 1;
 				} else {
 					print_string("Checksum incorrect! Aborting.\n");
 					slen = strtox(outbuf, "HTTP/1.1 400 Bad Request\r\nContent-Length: 33\r\n"
@@ -874,9 +870,10 @@ void httpd_appcall(void)
 	print_byte(s->tstate);
 	write_char(' ');
 #endif
-	if(uip_connected() && s->tstate == TSTATE_CLOSED) {
+	if(uip_connected()) {
 		dbg_string("Connected...\n");
 		s->tstate = TSTATE_NONE;
+		s->fw_reset_pending = 0; // explicitly initialize reused XDATA appstate
 	} else if (uip_closed()) {
 		dbg_string("Connection closed\n");
 		s->tstate = TSTATE_CLOSED;
@@ -928,7 +925,7 @@ void httpd_appcall(void)
 			cont_len -= slen;
 			cont_addr += slen;
 			s->tstate = TSTATE_TX;
-		} else if (fw_reset_pending) {
+		} else if (s->fw_reset_pending) {
 			// The upload verdict has been fully ACKed by the client;
 			// now it is safe to reset and apply the staged image
 			print_string("Resetting to apply update\n");