fix RST storm: stop proxy_feed after CLOSE sent + free unsent before tcp_close

src/tcp_proxy.c

@@ -187,7 +187,7 @@ static void transport_to_uip_cb(struct ll_queue* q, void* arg) {
 // Helper: feed data from transport_to_uip queue to lwIP TCP
 // ====================================================================
 static void proxy_feed_from_transport(struct proxy_conn *pc) {
-    if (!pc->transport_to_uip || !pc->pcb) return;
+    if (!pc->transport_to_uip || !pc->pcb || pc->closing_sent) return;
     int sent_any = 0;
     int entries_fed = 0;
     while (1) {
@@ -330,6 +330,7 @@ static err_t proxy_poll_cb(void *arg, struct tcp_pcb *pcb) {
         tcp_arg(save, NULL); pc->pcb = NULL;
         { uint16_t wnd_gap = TCP_WND_MAX(save) - save->rcv_wnd;
           if (wnd_gap > 0) tcp_recved(save, wnd_gap); }
+        while (save->unsent) { struct tcp_seg *seg = save->unsent; save->unsent = seg->next; u_free(seg); }
         tcp_close(save);
         struct tcp_proxy *proxy = pc->proxy;
         struct proxy_conn **prev = &proxy->conns;