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RTL8139 Ethernet with real TX/RX, ARP table, honest TCP status

Rewritten in Phase A6/C. The old register pokes never touched the wire. The current driver (net.c) is PCI-probed, builds correct frames, transmits through real TX descriptors, receives through an 8 KiB ring in the NIC interrupt, and learns an ARP table. Verified by capturing a real ARP request from the guest. TCP proper is still Phase D.

Contents

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Hardware and QEMU

ItemValue
NICRTL8139, I/O base + IRQ from PCI (QEMU: IRQ11)
MACRead from card IDR0–5 (52:54:00:12:34:56 on QEMU)
IPIP_ADDR 0x5DB8D822, gateway 0x0A000202, DNS 0x0A000203
QEMU-device rtl8139,netdev=n0 -netdev user,id=n0
RX8 KiB ring, ISR-driven + 10 Hz poll backup
TX4×1536 descriptors, round-robin

Driver (net.c / net.h)

net_init(): PCI scan for 10EC:8139 → IO BAR + IRQ + bus mastering;
  MAC from IDR; software reset; publish 8 KiB RX ring (RBSTART);
  RCR accept broadcast/match; IMR ROK+TOK; enable receiver+transmitter.
rtl_tx_raw(): copy frame to next TX buffer, ring TSAD/TSD descriptors.
net_rx_ring(): drain ring by CAPR/CURR pointers, learn ARP replies
  into an 8-entry table, flag packets for net_poll().
net_handler(): ISR — ack ISR register, drain RX, EOI both PICs.
net_poll(): returns 1 only when a packet arrived (no more forced
  redraws every 10 ticks).

Protocols

FunctionWhat it does
net_arp_request(gw)Build a correct 60-byte ARP request (broadcast dst, card MAC/IP) and transmit it
net_arp_lookup(ip, mac)Look up learned ARP table entries
send_tcp_synCraft a correct SYN (IP header + checksum, TCP header)
net_http_get(ip, path, buf, sz)Resolves MAC via ARP first (-1 = no reply); TCP handshake itself is Phase D (-2)
net_dns_resolve(host, ip)Stub: always returns IP_ADDR (Phase D)

Terminal and browser integration

PING   -> net_arp_request(net_get_gw()); learned MAC shown as
          GW MAC xx:xx:xx:xx:xx:xx, else "ARP SENT TO GW"
FETCH  -> "NO ARP REPLY" (-1) or "ARP OK, TCP IN PHASE D" (-2);
          no fake OK anymore
BROWSER -> toggle browser_open; "BROWSER OPEN/CLOSED"

The browser window (draw_browser_window()) strips <tags> and wraps at 44 columns × 8 rows. Empty state shows “WELCOME TO nexOS WEB / OPEN TERMINAL, TYPE FETCH”.

Limits

  • RX ring + ISR work; TCP receive state machine, retransmit and real DNS are Phase D.
  • No TLS (and none planned for the kernel).
  • IP is static; DHCP is Phase D.
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