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net: an interface that appears after boot starts the stack

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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
This commit is contained in:
Nexoniarz 2026-10-25 15:38:06 +01:00
commit a9d2e14004
3 changed files with 21 additions and 4 deletions
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5
kernel/net/lwip/netif_eth.c
View file

@ -110,6 +110,11 @@ net_eth_attach(struct device *dev)
if (nifs >= NETIF_MAX || dev == 0) if (nifs >= NETIF_MAX || dev == 0)
return -1; 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]; struct eth_if *e = &ifs[nifs];
e->dev = dev; e->dev = dev;

12
kernel/net/net.c
View file

@ -194,8 +194,16 @@ net_attach_late(struct device *d)
{ {
int idx; int idx;
if (!net_ready) // No stack yet. Either netinit() is still to run, or it ran on a machine
return -1; // netinit() has not run; it will pick this up // 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(); lwip_sys_lock();
idx = net_eth_attach(d); idx = net_eth_attach(d);

8
ldls/kpi/net.c
View file

@ -220,8 +220,12 @@ kpi_register_netdev(void *dev)
c.pad[0] = c.pad[1] = 0; c.pad[0] = c.pad[1] = 0;
c.name[0] = 'l'; c.name[1] = 'd'; c.name[2] = 'l'; c.name[3] = 's'; c.name[0] = 'l'; c.name[1] = 'd'; c.name[2] = 'l'; c.name[3] = 's';
if (ioctl(kpi.netfd, NETUSERIOC_CREATE, &c) < 0) { int r = ioctl(kpi.netfd, NETUSERIOC_CREATE, &c);
kpi_log("kpi: /dev/netdev is already somebody else's\n"); 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); close(kpi.netfd);
kpi.netfd = -1; kpi.netfd = -1;
return -1; return -1;