2a441af3c6
docs/plan/ldls.md L3a -- the class bridge, and the first of the three pieces
L3 turned out to be.
/dev/netdev is /dev/pci with the arrows reversed. That hands a device to a
process; this lets a process be one. The kernel side is netdev_ops and nothing
else -- transmit, receive, mac, link_up, the same four entries e1000
publishes -- so a process claims the device, supplies a MAC, and from then on
read() gives it frames the stack wants sent and write() hands it frames that
arrived.
cmd/netecho proves it and is deliberately not a driver: no hardware, none
claimed, every frame answered by the program itself. DHCP so the interface
gets an address at all, ARP so the stack can find it, ICMP so it can be
pinged. All built by hand from RFCs 826, 791, 792 and 2131.
# netecho &
netuser: ldls0 is a process now, 2:4c:44:4c:53:1
netecho: I am 10.9.0.1 and will offer 10.9.0.2
netecho: answered DHCP, offering an address
# cat /proc/netif
interface ldls0 driver netuser address 10.9.0.2 gateway 10.9.0.1
# ping 10.9.0.1 3
netecho: answered an ARP
netecho: answered a ping
3 packets transmitted, 3 received, 0% packet loss
The interface got its address by DHCP from a process and then answered ping
from one. lwIP never learns that the thing behind netdev_ops is not a driver,
which is the whole property the bridge exists to have.
It dies the way it should, too. kill the process and link_up() answers false
immediately, so the stack refuses to send -- "ping: sendto: -5" -- rather than
swallowing packets into a driver that is not there. Start another and the
*same* interface comes back, keeping its address. That came free:
netuser_release_all() sits beside pciuser_release_all() in exit() for exactly
the same reason, and the reason is that a process holding a device is one that
may crash.
One thing the kernel needed: netinit() starts DHCP on the devices that exist
when it runs, so an interface created later -- which is how an LDLS-hosted
driver arrives -- would have come up with no address and no way to get one.
net_attach_late() fixes that, and lives in kernel/net/net.c because that is
the only file allowed to include lwIP's headers.
Recorded as not done, because it is not: this proves the bridge, not a driver.
Nothing in that test loads a module. That is why it was done first -- if ping
had not worked here the bridge would be wrong, and now a failure with a real
driver can only be the driver's side. L3b is the SchOS-side host, L3c is the
fifteen symbols for real, and L3 is the two joined.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
128 lines
4 KiB
C
128 lines
4 KiB
C
#include "types.h"
|
|
#include "defs.h"
|
|
#include "param.h"
|
|
#include "spinlock.h"
|
|
#include "sleeplock.h"
|
|
#include "fs.h"
|
|
#include "file.h"
|
|
#include "x86.h"
|
|
#include "errno.h"
|
|
|
|
extern int consoleread(struct inode*, uint64, char*, int);
|
|
extern int consolewrite(struct inode*, uint64, char*, int);
|
|
extern int mouseread(struct inode*, uint64, char*, int);
|
|
|
|
static uint64 rseed = 0x2A99554433221100ULL;
|
|
|
|
int
|
|
nullwrite(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
return n;
|
|
}
|
|
|
|
int
|
|
nullread(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
int
|
|
zeroread(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
memset(dst, 0, n);
|
|
return n;
|
|
}
|
|
|
|
int
|
|
randomread(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
for(int i = 0; i < n; i++){
|
|
rseed = rseed * 6364136223846793005ULL + 1442695040888963407ULL;
|
|
dst[i] = (rseed >> 32) & 0xFF;
|
|
}
|
|
return n;
|
|
}
|
|
|
|
// /dev/full — reads as an endless run of zero bytes, every write fails with
|
|
// ENOSPC. Programs use it to exercise their out-of-disk-space paths.
|
|
int
|
|
fullwrite(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
return -ENOSPC;
|
|
}
|
|
|
|
int
|
|
mousewrite(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
return n;
|
|
}
|
|
|
|
int
|
|
memread(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
switch(ip->minor) {
|
|
case 1: return consoleread(ip, off, dst, n);
|
|
case 2: return nullread(ip, off, dst, n);
|
|
case 3: return consoleread(ip, off, dst, n);
|
|
/* 10 = /dev/tty, 11..16 = /dev/tty1..tty6. consoleread resolves the
|
|
minor to a terminal; see vt_for_minor(). */
|
|
case 10: case 11: case 12: case 13: case 14: case 15: case 16:
|
|
return consoleread(ip, off, dst, n);
|
|
case 5: return zeroread(ip, off, dst, n);
|
|
case 7: return zeroread(ip, off, dst, n); // /dev/full reads as zeros
|
|
case 8:
|
|
case 9: return randomread(ip, off, dst, n);
|
|
default: return -1;
|
|
}
|
|
}
|
|
|
|
int
|
|
memwrite(struct inode *ip, uint64 off, char *dst, int n)
|
|
{
|
|
switch(ip->minor) {
|
|
case 1: return consolewrite(ip, off, dst, n);
|
|
case 10: case 11: case 12: case 13: case 14: case 15: case 16:
|
|
return consolewrite(ip, off, dst, n);
|
|
case 7: return fullwrite(ip, off, dst, n); // /dev/full: always ENOSPC
|
|
case 2:
|
|
case 5:
|
|
case 8:
|
|
case 9: return nullwrite(ip, off, dst, n);
|
|
default: return -1;
|
|
}
|
|
}
|
|
|
|
struct devsw devsw[] = {
|
|
[0] = { 0, 0 },
|
|
[1] = { memread, memwrite },
|
|
// /dev/fb0 (major 2) — the framebuffer, kernel/dev/fb.c. This used to be
|
|
// { nullread, nullwrite }, so writing pixels to it succeeded and did
|
|
// nothing.
|
|
// The close hook gives the text console its screen back when whatever was
|
|
// drawing on the framebuffer exits — see fbclose().
|
|
[2] = { fbread, fbwrite, 0, fbclose },
|
|
[3] = { mouseread, mousewrite },
|
|
[4] = { 0, 0 },
|
|
// /dev/tty (major 5) — alias for the console
|
|
[5] = { memread, memwrite },
|
|
// /proc status files (major 6) — see kernel/dev/procfs.c
|
|
[6] = { procread, procwrite },
|
|
// /dev/input/eventN (major 7) — raw evdev events, kernel/dev/input.c. The
|
|
// minor is the device index, so event0 is the keyboard and event1 the mouse.
|
|
[7] = { inputread, inputwrite, inputready, inputclose, inputopen },
|
|
// /dev/hdN (major 8) — raw disks, kernel/dev/disk.c. The minor is the IDE
|
|
// device number. No `ready` hook: a disk is always ready, which is what
|
|
// fileread assumes when one is absent.
|
|
[8] = { diskread, diskwrite },
|
|
// /dev/pci (major 9) -- PCI devices reachable from userspace, for drivers
|
|
// that do not live in the kernel. Registers arrive through mmap and
|
|
// everything else through ioctl; see include/pciuser.h.
|
|
[9] = { pciuser_read, pciuser_write },
|
|
// /dev/dbg (major 10) -- ask the kernel a question. Write a line, read the
|
|
// answer; see include/dbg.h and docs/plan/debugger.md.
|
|
[10] = { dbg_read, dbg_write },
|
|
// /dev/netdev (major 11) -- a process, being a network interface. The
|
|
// reverse of major 9: that hands a device to a process, this lets a process
|
|
// be one. See include/netuser.h.
|
|
[11] = { netuser_read, netuser_write, netuser_ready },
|
|
};
|