From a9d2e140046908f62a52311d2eff4065635e4191 Mon Sep 17 00:00:00 2001
From: Nexoniarz <gamesfrank90@gmail.com>
Date: Sun, 25 Oct 2026 15:38:06 +0100
Subject: [PATCH] net: an interface that appears after boot starts the stack

With the native r8169 out of the registry, the TUF A15 boots with no
network device; netinit() saw none and left the stack off, and
net_attach_late() then refused every interface that came later -- its
comment assumed netinit() was still to run. Linux's r8169 under LDLS
got as far as registering ldls0 and was turned away. A late interface
now starts the stack, whose first act is to attach every device there
is; net_eth_attach() refuses a device it already has, for the window
in which both could offer it.

LDLS says which refusal it got: EBUSY is another process, anything else
is the kernel.

Tested in QEMU with -nic none and netecho: no interface at boot, then
ldls0 with a DHCP lease and ping answered.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
---
 kernel/net/lwip/netif_eth.c |  5 +++++
 kernel/net/net.c            | 12 ++++++++++--
 ldls/kpi/net.c              |  8 ++++++--
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/kernel/net/lwip/netif_eth.c b/kernel/net/lwip/netif_eth.c
index a16b5dd..764a178 100644
--- a/kernel/net/lwip/netif_eth.c
+++ b/kernel/net/lwip/netif_eth.c
@@ -110,6 +110,11 @@ net_eth_attach(struct device *dev)
 
     if (nifs >= NETIF_MAX || dev == 0)
         return -1;
+    // Once only: a device that appears while netd is starting can be offered
+    // both by netd's boot-time walk and by net_attach_late.
+    for (int i = 0; i < nifs; i++)
+        if (ifs[i].used && ifs[i].dev == dev)
+            return -1;
 
     struct eth_if *e = &ifs[nifs];
     e->dev  = dev;
diff --git a/kernel/net/net.c b/kernel/net/net.c
index 5fbc2b7..b526350 100644
--- a/kernel/net/net.c
+++ b/kernel/net/net.c
@@ -194,8 +194,16 @@ net_attach_late(struct device *d)
 {
     int idx;
 
-    if (!net_ready)
-        return -1;              // netinit() has not run; it will pick this up
+    // No stack yet. Either netinit() is still to run, or it ran on a machine
+    // with no network device and left the stack off -- which is every boot
+    // now that the laptop's RTL8168 is driven by a process (LDLS) that only
+    // appears later. Start it: net_thread's first act is to attach every
+    // network device there is, and that now includes this one.
+    if (!net_ready) {
+        if (!net_started)
+            netinit();
+        return net_started ? 0 : -1;
+    }
 
     lwip_sys_lock();
     idx = net_eth_attach(d);
diff --git a/ldls/kpi/net.c b/ldls/kpi/net.c
index e702a0d..ae8b14c 100644
--- a/ldls/kpi/net.c
+++ b/ldls/kpi/net.c
@@ -220,8 +220,12 @@ kpi_register_netdev(void *dev)
   c.pad[0] = c.pad[1] = 0;
   c.name[0] = 'l'; c.name[1] = 'd'; c.name[2] = 'l'; c.name[3] = 's';
 
-  if (ioctl(kpi.netfd, NETUSERIOC_CREATE, &c) < 0) {
-    kpi_log("kpi: /dev/netdev is already somebody else's\n");
+  int r = ioctl(kpi.netfd, NETUSERIOC_CREATE, &c);
+  if (r < 0) {
+    // -16 EBUSY is another process; anything else is the kernel refusing.
+    kpi_log(r == -16 ? "kpi: /dev/netdev is already somebody else's\n"
+                     : "kpi: the kernel would not take the interface, error ");
+    if (r != -16) { kpi_lognum(r); kpi_log("\n"); }
     close(kpi.netfd);
     kpi.netfd = -1;
     return -1;