From 233900c15eb635aa4d404b4d4b7a58aca30fadc9 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Fri, 23 Jan 2026 01:41:49 +0100
Subject: [PATCH] DEC Tulip: Reject transmissions with NO CARRIER error when
 link it down, fixes #6743.

---
 src/network/net_tulip.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/network/net_tulip.c b/src/network/net_tulip.c
index 298cda232..3f1825a1e 100644
--- a/src/network/net_tulip.c
+++ b/src/network/net_tulip.c
@@ -733,7 +733,9 @@ tulip_tx(TULIPState *s, struct tulip_descriptor *desc)
         if ((s->csr[6] >> CSR6_OM_SHIFT) & CSR6_OM_MASK) {
             /* Internal or external Loopback */
             tulip_receive(s, s->tx_frame, s->tx_frame_len);
-        } else if (s->tx_frame_len <= sizeof(s->tx_frame)) {
+        } else if (net_cards_conf[s->nic->card_num].link_state & NET_LINK_DOWN)
+            desc->status |= (TDES0_ES | TDES0_NC);
+        else if (s->tx_frame_len <= sizeof(s->tx_frame)) {
             //pclog("Transmit!.\n");
             network_tx(s->nic, s->tx_frame, s->tx_frame_len);
         }