From 26a2ccb8368a9968b6ec16068ad68dd0edb40641 Mon Sep 17 00:00:00 2001
From: user <user@clank>
Date: Fri, 17 Jul 2026 12:54:43 +0200
Subject: net: UDP sockets in the kernel + a DNS resolver (real hostname
 lookups)

Adds UDP to the kernel socket layer on top of the ICMP core:
- net_sum() (raw folded sum) split out of net_cksum() so a UDP pseudo-header
  (src/dst IP + proto + length) can seed the segment checksum.
- udp_send: builds IP+UDP with the pseudo-header checksum; NET_BIND sets the
  local/source port; net_connect sets the peer.
- udp_in: demuxes inbound UDP by destination port to the bound socket
  (net_find_udp), delivers the payload + source addr.

Also fixes a real recv bug: net_pump clobbers BC/DE/HL, so the old recv timeout
counted in registers and was effectively random. recv now counts in WRAM.

New `nslookup HOST` (PROG_NSLOOKUP=28, bank 30): builds a DNS A query and parses
the answer (with 0xC0 name-compression) entirely in userland over a UDP socket -
the kernel never sees DNS, just UDP. Verified through the bridge NAT:
    /# nslookup example.com   ->  example.com -> 172.66.147.243

This gives us name resolution for the TCP/HTTP demo next.
---
 Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'Makefile')

diff --git a/Makefile b/Makefile
index fa642ad..e3bad9d 100644
--- a/Makefile
+++ b/Makefile
@@ -20,7 +20,7 @@ $(BUILD)/%.o: src/%.asm | $(BUILD)
 # C programs: compiled with SDCC into ROM-bank blobs and INCBIN'd by programs.asm
 CBLOBS := c/chello.bin c/echo.bin c/true.bin c/false.bin c/uname.bin \
           c/pid.bin c/cat.bin c/wc.bin c/head.bin c/args.bin \
-          c/ls.bin c/save.bin c/rm.bin c/sh.bin c/ps.bin c/kill.bin c/spin.bin c/blk.bin c/mkdir.bin c/count.bin c/ptest.bin c/necho.bin c/wget.bin c/chat.bin c/netd.bin c/ping.bin
+          c/ls.bin c/save.bin c/rm.bin c/sh.bin c/ps.bin c/kill.bin c/spin.bin c/blk.bin c/mkdir.bin c/count.bin c/ptest.bin c/necho.bin c/wget.bin c/chat.bin c/netd.bin c/ping.bin c/nslookup.bin
 $(BUILD)/programs.o: $(CBLOBS)
 
 # C programs also depend on the shared libc sources
-- 
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